Is not fasting before cardiac catheterisation better than fasting? A systematic integrative literature review
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Coronary artery disease (CAD) is the leading cause of death internationally and the second leading cause of death in New Zealand.[[1,2]] The disease carries a significant health burden and affects more than 170,000 individuals across New Zealand.[[3]] Cardiac catheterisation is the gold standard test for diagnosis of coronary artery disease.[[4]] This procedure is minimally invasive and usually completed under conscious sedation. In recent years, the risks associated with this procedure have decreased substantially due to the development of equipment, peri-procedural care and operator experience.[[5]] Accordingly, diagnostic angiography is commonly completed as an outpatient procedure, with many elective angioplasties following the same trend.[[6]]
Historically, patients undergoing coronary angiography and angioplasty have been required to fast in preparation for this procedure.[[7,8]] However, scholars have questioned the evidence base for this practice, with some centres changing guidelines to remove fasting altogether.[[9,10]] Concerns regarding eating before procedures relate to the possible increased risk for pulmonary aspiration, a serious event that can lead to pneumonia, respiratory compromise and death.[[11,12]] However, fasting patients for an extended period could put patients at higher risk of other complications, including hypotension, contrast-induced nephropathy and hypoglycaemia.[[5,13]] Allowing patients to eat and drink before coronary angiography positively affects the individual’s experience, improves patient satisfaction and reduces anxiety.[[14–16]] In this context, we aimed to synthesise current international evidence about not fasting before cardiac catheterisation.
Methods
We used an integrative review to synthesise current evidence about not fasting before coronary angiography and angioplasty. The integrative method is the broadest type of review, allowing the inclusion of studies with diverse methodologies, including both empirical and theoretical publications.[[17,18]] This systematic approach facilitates an in-depth analysis and captures varied perspectives on a topic without the focus on hierarchical evidence types.[[17,18]]
Searches were carried out via title, subject and keyword using the following online databases: MEDLINE, Scopus, the Cumulative Index to Nursing and Allied Health Literature (CINAHL Plus), Cochrane and Web of Science. The search terms listed in Table 1 captured variations of the terms “non-fasted,” “fasted,” “before,” “coronary angiography” and “coronary angioplasty.” Terms were combined using Boolean operators. Inclusion and exclusion criteria are listed in Table 2.
The initial search yielded 1,531 papers. After the removal of duplicates and screening by title and abstract, seven studies remained and were screened by full text. Four papers were added through reference checking and screened. Of these 11, nine studies were included in the review (Figure 1).
Table 1: Search terms.
Table 2: Inclusion and exclusion criteria.
Figure 1: Flowchart of literature selection process.
Data extraction was completed using a standard pro forma and included: relevance to the research question, study design and limitations.[[19]] Studies were then assessed for quality and methodological rigour (Table 3). For research reviews, no gold standard for quality scores exists; the diversity of methodologies means criteria for quality assessment are variable.[[17]] We chose the quantitative assessment tool developed by Hawker et al[[20]] to assess empirical studies and abstracts. This tool evaluates each section of the study, including abstract, research aims and background, methodology and sampling, data collection and analysis, ethics and bias and research findings. Overall, the quality of available evidence was low. The quality of evidence published by Hamid et al[[9]] and Bacus et al[[14]] were rated as fair. The abstracts from Mishra et al[[15]] and Li et al[[21]] were rated as poor as they did not provide sufficient information to accurately assess some article sections using the evaluation tool. The opinion pieces, study protocols and nursing guidelines were considered grey literature and were not formally scored for quality.[[22]]
The process of thematic data analysis followed the six-phase approach outlined by Braun and Clarke: familiarisation with data, generating initial codes, searching for themes, reviewing themes, defining and naming themes and producing the report.[[23]] Data from all studies were extracted and coded. Codes were catalogued and grouped in Microsoft Excel to allow for identification of themes. This theme-based approach to data extraction allowed information from a variety of sources to be compared and combined.[[24]]
Table 3: Evidence on not fasting before cardiac catheterisation. View Table 3.
Results
Of the nine studies included in this review, there was one retrospective observational analysis of a data registry,[[9]] one prospective observational study[[14]] and two abstracts of randomised controlled trials from conference proceedings.[[15,21]] There were three opinion pieces (two of which provided commentary on other studies included in this review),[[16,26,27]] one published clinical guideline[[28]] and one record from a clinical trials register.[[25]] Three studies discussed both coronary angiography and angioplasty[[14,21,25]] and five studies discussed coronary angioplasty only.[[9,16,26–28]] One study did not outline whether included participants underwent coronary angiography or angioplasty.[[15]] Seven studies commented on the incidence of outcomes associated with fasting or not fasting.[[9,14–16,21,25,26]] Of the four empirical studies, one was completed in the United Kingdom,[[9]] one in New Zealand,[[14]] one in Singapore[[21]] and one in the United States of America.[[15]] The planned study, found on the clinical trial registry, will be completed in the United Kingdom.[[25]]
Two full-text empirical studies were identified, one with 1916 participants involved[[9]] and the second with 1,030 participants.[[14]] Abdelaziz[[25]] has indicated an intention to complete a randomised controlled trial involving 600 participants. Their study outline hypothesises that there will be no difference in the incidence of procedural complications between non-fasted and fasted groups and that the non-fasted groups will have a lower incidence of hypoglycaemia and hypotension.[[25]] This is similar to Hamid et al[[9]] and Li et al,[[21]] who aimed to show the safety of not fasting before coronary angiography and angioplasty. Three studies concluded that their results demonstrated the safety of this practice.[[9,15,21]]
Thematic analysis identified the following three themes related to not fasting before cardiac catheterisation:
- Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management.
- Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting.
- Current practice, evidence and guidelines are inconsistent and further study is required.
Theme 1: fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management
The benefits of fasting found in this literature search are centred around mitigating the possible risks associated with not fasting. Fasting is thought to reduce the risk of vomiting, bronchial aspiration and resulting pneumonia.[[9,14,26]] However, Hamid et al[[16]] suggest that the increased risk of aspiration in unfasted patients is unfounded. There is also a perceived benefit of fasting due to the possibility of proceeding to emergency surgery and the need for general anaesthesia.[[9,28]] For this reason, patients routinely fast from four to eight hours before coronary angiography.[[9,14,26]] Hamid et al[[9]] claim that the benefits of fasting before coronary angiography and angioplasty are not evidence-based, as little evidence exists. Hamid et al[[16]] suggest that the risk associated with not fasting has been overstated and that those who fast may be at greater risk of complications. Interestingly, individuals presenting with an acute requirement for angioplasty did not fast before the procedure.[[16]] Further, there are limited reports of excess peri-procedural pulmonary aspiration or related complications during emergency coronary artery bypass grafting in the unfasted patient.[[16,25]]
Theme 2: not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting
Coronary angiography is considered a safe procedure, which brings into question the need for fasting in preparation.[[26]] In one study involving 1,916 angioplasty patients over three years, only two patients (0.1%) required subsequent emergency coronary artery bypass grafting surgery.[[9]] Also, none of the patients in this population fasted, and yet none required intubation during the angioplasty procedure and there were no episodes of aspiration pneumonia. Similarly, Bacus et al[[14]] reported that, among 1,030 elective coronary angiography and angioplasty patients, there were no episodes of aspiration. Mishra et al[[15]] recorded one episode of aspiration pneumonitis in the non-fasting group of 253 inpatients, and this did not represent a statistically significant difference between the non-fasting and fasting groups. The outcomes of small-scale studies demonstrate that reducing or eliminating fasting before coronary angiography and angioplasty may be safe. However, further studies are needed to explore this.[[9,21,26]]
The benefits of not fasting before cardiac catheterisation are mostly perceived rather than evidence-based. Scholars hypothesise that allowing patients to eat and drink up to the time of their procedure will increase their level of hydration, reduce the risk of contrast-induced nephropathy, improve vascular access and reduce peri-procedural hypotension and hypoglycaemia.[[9,14,16,21]] Fasting-related procedural delay and cancellation is thought to significantly impact patients and optimal health resource allocation.[[14]] These delays can be avoided, and hospital stays potentially shortened, if patients are allowed to eat pre-procedure.[[9,16,25]] Scholars also predict that non-fasting patients may be less anxious before their procedure.[[16]] Following preliminary analysis, Mishra et al[[15]] reported that non-fasting patients had a significantly higher patient satisfaction score and a lower cost of index hospitalisation compared to the fasting group.
Pre-procedural fasting is associated with risk and possible complications. In a randomised trial, patients that were allowed to eat up to two hours before angiography had a lower incidence of hypotension requiring a fluid bolus (4% vs 9.4%) and a lower incidence of nausea (0% vs 0.8%) when compared to those who had fasted overnight.[[21]] However, patients that were fasted for less time also required a larger dose of sedation (6.8% vs 2.6%) as a result of anxiety or arterial spasm.[[21]] Mishra et al[[15]] compared patients who fasted solids from midnight and clear fluids from two hours before the procedure to patients who were allowed to eat and drink until the time of the procedure. There was no statistically significant difference between the two groups for incidence of adverse events, such as peri-procedural hypotension, contrast-induced nephropathy, hypoglycaemia, hyperglycaemia, nausea, vomiting and 30-day mortality. In the study completed by Bacus et al[[14]] , 47% of patients with a mean fasting time of 11.6 hours reported feeling hungry, and 11.6% reported headaches. Prolonged periods of fasting is thought to increase insulin resistance, potentially exacerbating the metabolic response following trauma.[[16]] Additionally, patients who are fasting may be less likely to take their morning medication, including anti-hypertensives, leading to poorly controlled hypertension.[[9]] Bacus et al[[14]] reported eight episodes of hyperglycaemia and seven episodes of hypoglycaemia, suggesting that this may have been due to missed medications and prolonged fasting. Fasted individuals, particularly the older age group, are at risk of dehydration, hypoglycaemia and contrast-induced nephropathy.[[9,26]] Such complications could lead to a prolonged hospital stay with economic and health implications.[[9]]
Theme 3: current practice, evidence and guidelines are inconsistent and further study is required
Data available in this review indicate there is an inconsistency in practices between institutions. In New Zealand, one hospital guideline recommended fasting patients for four to six hours.[[14]] The practice in two district general hospitals in the United Kingdom was that no patients were fasted in preparation for cardiac catheterisation.[[9]] In Singapore, standard practice in one hospital was to fast patients from midnight for both elective and in-hospital cardiac catheterisation.[[21]] The duration of fasting within a New Zealand institution was variable, with patients fasting anywhere between zero and 24 hours before their procedure.[[14]] The mean fasting time of 11.6 hours was greater than anticipated considering the maximum recommended duration for fasting was six hours.[[14]] In emergencies, however, angioplasty is performed urgently without any fasting restrictions.[[9,26]] Current practice in this context is based on limited scientific evidence and may have developed from fasting guidelines for general anaesthesia.[[9,14,16,25–27]] According to Wijeyeratne et al,[[27]] the evidence base relating to this practice and the optimal period of fasting has been “exceedingly slow to develop.”
Authors of papers included in this review claim that there are no available fasting guidelines specific to coronary angiography and angioplasty.[[9,16,26]] Instead, information and opinion identified in this review suggest that practice is based on local hospital and health board guidelines, which are considered inconsistent and unsubstantiated.[[9,25,27,28]] Protocols and guidelines such as this require revision.[[26]] Clinical nursing guidelines for angioplasty published in 2011 state that, given the available evidence, routine fasting for coronary angioplasty “is not justifiable; fasting should be based on clinical judgement on a case-by-case basis.”[[28]] However, the grade of this recommendation was documented as low, and consensus among the panel of clinical experts had not been reached. Clinicians are encouraged to “follow local policy and procedures.”[[28]]
Although both Hamid et al[[9]] and Mishra et al[[15]] suggest that their research demonstrates patients do not require fasting before coronary angioplasty, this review identified that there is consensus on the need for further study.[[9,16,21,26,27]] Future research should involve larger cohorts and multiple centres in randomised controlled trials in order to support interventional cardiologists to change from their current practice.[[ 9,16,21,26,27]] Studies currently underway aim to record the incidence of outcomes related to fasting and not fasting, such as contrast-induced nephropathy, hypotension, nausea, vomiting, emergency intubation, aspiration pneumonia, hyperglycaemia, hypoglycaemia and patient satisfaction.[[15,25]]
Discussion
Overall, analysis of the nine papers in this review identified limited evidence about not fasting before cardiac catheterisation. Thematic synthesis revealed that, although not fasting in this context is generally considered to be safe, there is still concern with implementing this practice in a clinical setting. This review identified that the potential for vomiting and pulmonary aspiration are two significant concerns associated with not fasting before coronary angiography and angioplasty. Vomiting, nausea and allergic reactions were once common complications of angiography due to the hypertonic nature of first-generation contrast dye.[[29]] In some reports, reactions to contrast dye occurred in over 50% of cases.[[30]] Such reactions could be why fasting was once a relevant choice for cardiac catheterisation. However, contrast dye used today is low-osmolality and non-ionic, and the reported rate of vomiting is low (0.8%).[[5]] Similarly, the risk of requiring emergency surgery has reduced significantly in recent years and is reported at around 0.14% in the contemporary setting.[[31]] These diminishing risks question the necessity of this practice.[[14]]
Although there is limited recent evidence to support fasting in this context, this practice continues to be widely enforced and supported by healthcare professionals. The recommendation of fasting before cardiac catheterisation is based on perceived risk, and it does not acknowledge the potential risk associated with fasting. It may be that physicians are more concerned by rare events with potentially severe outcomes than the possibility of more common adverse events with lesser effects from not fasting. For example, the perceived risk of aspiration causing serious harm for a small number of individuals may be over-emphasised in the context of the general wellbeing and comfort of the majority of patients. Although this is understandable, it limits the opportunity to foster the potential safe and beneficial outcomes of not fasting in this context. Indeed, in the randomised controlled trial by Mishra et al,[[15]] unfasted patients reported higher satisfaction scores following cardiac catheterisation compared to those who fasted.
Research in other fields does not show a connection between not fasting and vomiting or aspiration when patients receive conscious sedation. In a study of cerebral angiography by Kwon et al,[[32]] there was no statistical difference in nausea and vomiting between fasting and non-fasting groups, and there were no cases of pulmonary aspiration among 2,554 patients. The overall incidence of nausea and vomiting was low, reported at 1.05%. Similarly, a systematic review of various procedures involving conscious sedation found no episodes of aspiration in unfasted patients undergoing procedures other than endoscopy.[[33]] Research regarding procedural sedation in the emergency department has shown no association between fasting duration and the incidence of vomiting and other complications.[[12,34,35]] Indeed, current recommendations for conscious sedation in the emergency department state that fasting is not required when verbal contact is maintained.[[36]]
The overall quality of evidence included in the review was assessed as poor when compared to empirical evidence, as it is based predominantly on expert opinion.[[22,37]] However, the quality of grey literature is variable, and its inclusion can be important in reducing publication bias and providing contextual factors.[[38]] The low quality of evidence identified by this review limits understanding of the safety of not fasting and its future utility. Further, there is no consensus among experts for recommendations in this area and practice varies greatly between and within hospitals.[[9,14,21,25,26,28]] Indeed, current guidelines and local practices may not be based on scientific evidence. We argue that further investigation into the risks and benefits of not fasting before cardiac catheterisation is warranted.
Conclusion
This is the first systematic review to synthesise evidence about not fasting before coronary angiography and angioplasty. It has revealed limited evidence regarding this practice. Thematic analysis of nine studies demonstrates that current fasting practices are based on managing perceived risk and that not fasting before angiography is generally considered safe and beneficial for the patient. Due to the gap in knowledge that exists regarding this topic, there is significant potential for future research, both locally and internationally. Future multi-centre randomised controlled trials will build a reliable and robust knowledge base on this topic. It appears that the ongoing concerns around not fasting are related to perceived risk, rather than actual risk. However, further research is needed in this area to support policy and practice change on a large scale.
Summary
Historically, patients undergoing cardiac catheterisation have not been allowed to eat or drink for at least six hours prior to their procedure. Fasting in this context has recently been questioned by scholars around the world. This literature review has shown that being able to eat and drink in the lead up to this procedure is considered safe and beneficial for the patient. However, guidelines and practices are inconsistent and further research needs to be done to encourage hospitals around New Zealand and across the world to change their practice.
Abstract
Aim
To synthesise international evidence about not fasting before cardiac catheterisation.
Method
We used a systematic, integrative literature review and applied quality assessment criteria.
Results
Nine of 1,535 articles met the inclusion criteria. Critique and analysis of the literature revealed three themes: (1) Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management. (2) Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting. (3) Current practice, evidence and guidelines are inconsistent.
Conclusion
Ongoing concerns regarding not fasting before cardiac catheterisation are related to perceived risk, not actual risk. Indeed, this review indicates that not fasting may optimise patient experience. Further large-scale research is needed in this area to support policy and practice change to a patient-centric fasting protocol.
Author Information
Acknowledgements
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Competing Interests
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Is not fasting before cardiac catheterisation better than fasting? A systematic integrative literature review
View Article PDF
Coronary artery disease (CAD) is the leading cause of death internationally and the second leading cause of death in New Zealand.[[1,2]] The disease carries a significant health burden and affects more than 170,000 individuals across New Zealand.[[3]] Cardiac catheterisation is the gold standard test for diagnosis of coronary artery disease.[[4]] This procedure is minimally invasive and usually completed under conscious sedation. In recent years, the risks associated with this procedure have decreased substantially due to the development of equipment, peri-procedural care and operator experience.[[5]] Accordingly, diagnostic angiography is commonly completed as an outpatient procedure, with many elective angioplasties following the same trend.[[6]]
Historically, patients undergoing coronary angiography and angioplasty have been required to fast in preparation for this procedure.[[7,8]] However, scholars have questioned the evidence base for this practice, with some centres changing guidelines to remove fasting altogether.[[9,10]] Concerns regarding eating before procedures relate to the possible increased risk for pulmonary aspiration, a serious event that can lead to pneumonia, respiratory compromise and death.[[11,12]] However, fasting patients for an extended period could put patients at higher risk of other complications, including hypotension, contrast-induced nephropathy and hypoglycaemia.[[5,13]] Allowing patients to eat and drink before coronary angiography positively affects the individual’s experience, improves patient satisfaction and reduces anxiety.[[14–16]] In this context, we aimed to synthesise current international evidence about not fasting before cardiac catheterisation.
Methods
We used an integrative review to synthesise current evidence about not fasting before coronary angiography and angioplasty. The integrative method is the broadest type of review, allowing the inclusion of studies with diverse methodologies, including both empirical and theoretical publications.[[17,18]] This systematic approach facilitates an in-depth analysis and captures varied perspectives on a topic without the focus on hierarchical evidence types.[[17,18]]
Searches were carried out via title, subject and keyword using the following online databases: MEDLINE, Scopus, the Cumulative Index to Nursing and Allied Health Literature (CINAHL Plus), Cochrane and Web of Science. The search terms listed in Table 1 captured variations of the terms “non-fasted,” “fasted,” “before,” “coronary angiography” and “coronary angioplasty.” Terms were combined using Boolean operators. Inclusion and exclusion criteria are listed in Table 2.
The initial search yielded 1,531 papers. After the removal of duplicates and screening by title and abstract, seven studies remained and were screened by full text. Four papers were added through reference checking and screened. Of these 11, nine studies were included in the review (Figure 1).
Table 1: Search terms.
Table 2: Inclusion and exclusion criteria.
Figure 1: Flowchart of literature selection process.
Data extraction was completed using a standard pro forma and included: relevance to the research question, study design and limitations.[[19]] Studies were then assessed for quality and methodological rigour (Table 3). For research reviews, no gold standard for quality scores exists; the diversity of methodologies means criteria for quality assessment are variable.[[17]] We chose the quantitative assessment tool developed by Hawker et al[[20]] to assess empirical studies and abstracts. This tool evaluates each section of the study, including abstract, research aims and background, methodology and sampling, data collection and analysis, ethics and bias and research findings. Overall, the quality of available evidence was low. The quality of evidence published by Hamid et al[[9]] and Bacus et al[[14]] were rated as fair. The abstracts from Mishra et al[[15]] and Li et al[[21]] were rated as poor as they did not provide sufficient information to accurately assess some article sections using the evaluation tool. The opinion pieces, study protocols and nursing guidelines were considered grey literature and were not formally scored for quality.[[22]]
The process of thematic data analysis followed the six-phase approach outlined by Braun and Clarke: familiarisation with data, generating initial codes, searching for themes, reviewing themes, defining and naming themes and producing the report.[[23]] Data from all studies were extracted and coded. Codes were catalogued and grouped in Microsoft Excel to allow for identification of themes. This theme-based approach to data extraction allowed information from a variety of sources to be compared and combined.[[24]]
Table 3: Evidence on not fasting before cardiac catheterisation. View Table 3.
Results
Of the nine studies included in this review, there was one retrospective observational analysis of a data registry,[[9]] one prospective observational study[[14]] and two abstracts of randomised controlled trials from conference proceedings.[[15,21]] There were three opinion pieces (two of which provided commentary on other studies included in this review),[[16,26,27]] one published clinical guideline[[28]] and one record from a clinical trials register.[[25]] Three studies discussed both coronary angiography and angioplasty[[14,21,25]] and five studies discussed coronary angioplasty only.[[9,16,26–28]] One study did not outline whether included participants underwent coronary angiography or angioplasty.[[15]] Seven studies commented on the incidence of outcomes associated with fasting or not fasting.[[9,14–16,21,25,26]] Of the four empirical studies, one was completed in the United Kingdom,[[9]] one in New Zealand,[[14]] one in Singapore[[21]] and one in the United States of America.[[15]] The planned study, found on the clinical trial registry, will be completed in the United Kingdom.[[25]]
Two full-text empirical studies were identified, one with 1916 participants involved[[9]] and the second with 1,030 participants.[[14]] Abdelaziz[[25]] has indicated an intention to complete a randomised controlled trial involving 600 participants. Their study outline hypothesises that there will be no difference in the incidence of procedural complications between non-fasted and fasted groups and that the non-fasted groups will have a lower incidence of hypoglycaemia and hypotension.[[25]] This is similar to Hamid et al[[9]] and Li et al,[[21]] who aimed to show the safety of not fasting before coronary angiography and angioplasty. Three studies concluded that their results demonstrated the safety of this practice.[[9,15,21]]
Thematic analysis identified the following three themes related to not fasting before cardiac catheterisation:
- Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management.
- Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting.
- Current practice, evidence and guidelines are inconsistent and further study is required.
Theme 1: fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management
The benefits of fasting found in this literature search are centred around mitigating the possible risks associated with not fasting. Fasting is thought to reduce the risk of vomiting, bronchial aspiration and resulting pneumonia.[[9,14,26]] However, Hamid et al[[16]] suggest that the increased risk of aspiration in unfasted patients is unfounded. There is also a perceived benefit of fasting due to the possibility of proceeding to emergency surgery and the need for general anaesthesia.[[9,28]] For this reason, patients routinely fast from four to eight hours before coronary angiography.[[9,14,26]] Hamid et al[[9]] claim that the benefits of fasting before coronary angiography and angioplasty are not evidence-based, as little evidence exists. Hamid et al[[16]] suggest that the risk associated with not fasting has been overstated and that those who fast may be at greater risk of complications. Interestingly, individuals presenting with an acute requirement for angioplasty did not fast before the procedure.[[16]] Further, there are limited reports of excess peri-procedural pulmonary aspiration or related complications during emergency coronary artery bypass grafting in the unfasted patient.[[16,25]]
Theme 2: not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting
Coronary angiography is considered a safe procedure, which brings into question the need for fasting in preparation.[[26]] In one study involving 1,916 angioplasty patients over three years, only two patients (0.1%) required subsequent emergency coronary artery bypass grafting surgery.[[9]] Also, none of the patients in this population fasted, and yet none required intubation during the angioplasty procedure and there were no episodes of aspiration pneumonia. Similarly, Bacus et al[[14]] reported that, among 1,030 elective coronary angiography and angioplasty patients, there were no episodes of aspiration. Mishra et al[[15]] recorded one episode of aspiration pneumonitis in the non-fasting group of 253 inpatients, and this did not represent a statistically significant difference between the non-fasting and fasting groups. The outcomes of small-scale studies demonstrate that reducing or eliminating fasting before coronary angiography and angioplasty may be safe. However, further studies are needed to explore this.[[9,21,26]]
The benefits of not fasting before cardiac catheterisation are mostly perceived rather than evidence-based. Scholars hypothesise that allowing patients to eat and drink up to the time of their procedure will increase their level of hydration, reduce the risk of contrast-induced nephropathy, improve vascular access and reduce peri-procedural hypotension and hypoglycaemia.[[9,14,16,21]] Fasting-related procedural delay and cancellation is thought to significantly impact patients and optimal health resource allocation.[[14]] These delays can be avoided, and hospital stays potentially shortened, if patients are allowed to eat pre-procedure.[[9,16,25]] Scholars also predict that non-fasting patients may be less anxious before their procedure.[[16]] Following preliminary analysis, Mishra et al[[15]] reported that non-fasting patients had a significantly higher patient satisfaction score and a lower cost of index hospitalisation compared to the fasting group.
Pre-procedural fasting is associated with risk and possible complications. In a randomised trial, patients that were allowed to eat up to two hours before angiography had a lower incidence of hypotension requiring a fluid bolus (4% vs 9.4%) and a lower incidence of nausea (0% vs 0.8%) when compared to those who had fasted overnight.[[21]] However, patients that were fasted for less time also required a larger dose of sedation (6.8% vs 2.6%) as a result of anxiety or arterial spasm.[[21]] Mishra et al[[15]] compared patients who fasted solids from midnight and clear fluids from two hours before the procedure to patients who were allowed to eat and drink until the time of the procedure. There was no statistically significant difference between the two groups for incidence of adverse events, such as peri-procedural hypotension, contrast-induced nephropathy, hypoglycaemia, hyperglycaemia, nausea, vomiting and 30-day mortality. In the study completed by Bacus et al[[14]] , 47% of patients with a mean fasting time of 11.6 hours reported feeling hungry, and 11.6% reported headaches. Prolonged periods of fasting is thought to increase insulin resistance, potentially exacerbating the metabolic response following trauma.[[16]] Additionally, patients who are fasting may be less likely to take their morning medication, including anti-hypertensives, leading to poorly controlled hypertension.[[9]] Bacus et al[[14]] reported eight episodes of hyperglycaemia and seven episodes of hypoglycaemia, suggesting that this may have been due to missed medications and prolonged fasting. Fasted individuals, particularly the older age group, are at risk of dehydration, hypoglycaemia and contrast-induced nephropathy.[[9,26]] Such complications could lead to a prolonged hospital stay with economic and health implications.[[9]]
Theme 3: current practice, evidence and guidelines are inconsistent and further study is required
Data available in this review indicate there is an inconsistency in practices between institutions. In New Zealand, one hospital guideline recommended fasting patients for four to six hours.[[14]] The practice in two district general hospitals in the United Kingdom was that no patients were fasted in preparation for cardiac catheterisation.[[9]] In Singapore, standard practice in one hospital was to fast patients from midnight for both elective and in-hospital cardiac catheterisation.[[21]] The duration of fasting within a New Zealand institution was variable, with patients fasting anywhere between zero and 24 hours before their procedure.[[14]] The mean fasting time of 11.6 hours was greater than anticipated considering the maximum recommended duration for fasting was six hours.[[14]] In emergencies, however, angioplasty is performed urgently without any fasting restrictions.[[9,26]] Current practice in this context is based on limited scientific evidence and may have developed from fasting guidelines for general anaesthesia.[[9,14,16,25–27]] According to Wijeyeratne et al,[[27]] the evidence base relating to this practice and the optimal period of fasting has been “exceedingly slow to develop.”
Authors of papers included in this review claim that there are no available fasting guidelines specific to coronary angiography and angioplasty.[[9,16,26]] Instead, information and opinion identified in this review suggest that practice is based on local hospital and health board guidelines, which are considered inconsistent and unsubstantiated.[[9,25,27,28]] Protocols and guidelines such as this require revision.[[26]] Clinical nursing guidelines for angioplasty published in 2011 state that, given the available evidence, routine fasting for coronary angioplasty “is not justifiable; fasting should be based on clinical judgement on a case-by-case basis.”[[28]] However, the grade of this recommendation was documented as low, and consensus among the panel of clinical experts had not been reached. Clinicians are encouraged to “follow local policy and procedures.”[[28]]
Although both Hamid et al[[9]] and Mishra et al[[15]] suggest that their research demonstrates patients do not require fasting before coronary angioplasty, this review identified that there is consensus on the need for further study.[[9,16,21,26,27]] Future research should involve larger cohorts and multiple centres in randomised controlled trials in order to support interventional cardiologists to change from their current practice.[[ 9,16,21,26,27]] Studies currently underway aim to record the incidence of outcomes related to fasting and not fasting, such as contrast-induced nephropathy, hypotension, nausea, vomiting, emergency intubation, aspiration pneumonia, hyperglycaemia, hypoglycaemia and patient satisfaction.[[15,25]]
Discussion
Overall, analysis of the nine papers in this review identified limited evidence about not fasting before cardiac catheterisation. Thematic synthesis revealed that, although not fasting in this context is generally considered to be safe, there is still concern with implementing this practice in a clinical setting. This review identified that the potential for vomiting and pulmonary aspiration are two significant concerns associated with not fasting before coronary angiography and angioplasty. Vomiting, nausea and allergic reactions were once common complications of angiography due to the hypertonic nature of first-generation contrast dye.[[29]] In some reports, reactions to contrast dye occurred in over 50% of cases.[[30]] Such reactions could be why fasting was once a relevant choice for cardiac catheterisation. However, contrast dye used today is low-osmolality and non-ionic, and the reported rate of vomiting is low (0.8%).[[5]] Similarly, the risk of requiring emergency surgery has reduced significantly in recent years and is reported at around 0.14% in the contemporary setting.[[31]] These diminishing risks question the necessity of this practice.[[14]]
Although there is limited recent evidence to support fasting in this context, this practice continues to be widely enforced and supported by healthcare professionals. The recommendation of fasting before cardiac catheterisation is based on perceived risk, and it does not acknowledge the potential risk associated with fasting. It may be that physicians are more concerned by rare events with potentially severe outcomes than the possibility of more common adverse events with lesser effects from not fasting. For example, the perceived risk of aspiration causing serious harm for a small number of individuals may be over-emphasised in the context of the general wellbeing and comfort of the majority of patients. Although this is understandable, it limits the opportunity to foster the potential safe and beneficial outcomes of not fasting in this context. Indeed, in the randomised controlled trial by Mishra et al,[[15]] unfasted patients reported higher satisfaction scores following cardiac catheterisation compared to those who fasted.
Research in other fields does not show a connection between not fasting and vomiting or aspiration when patients receive conscious sedation. In a study of cerebral angiography by Kwon et al,[[32]] there was no statistical difference in nausea and vomiting between fasting and non-fasting groups, and there were no cases of pulmonary aspiration among 2,554 patients. The overall incidence of nausea and vomiting was low, reported at 1.05%. Similarly, a systematic review of various procedures involving conscious sedation found no episodes of aspiration in unfasted patients undergoing procedures other than endoscopy.[[33]] Research regarding procedural sedation in the emergency department has shown no association between fasting duration and the incidence of vomiting and other complications.[[12,34,35]] Indeed, current recommendations for conscious sedation in the emergency department state that fasting is not required when verbal contact is maintained.[[36]]
The overall quality of evidence included in the review was assessed as poor when compared to empirical evidence, as it is based predominantly on expert opinion.[[22,37]] However, the quality of grey literature is variable, and its inclusion can be important in reducing publication bias and providing contextual factors.[[38]] The low quality of evidence identified by this review limits understanding of the safety of not fasting and its future utility. Further, there is no consensus among experts for recommendations in this area and practice varies greatly between and within hospitals.[[9,14,21,25,26,28]] Indeed, current guidelines and local practices may not be based on scientific evidence. We argue that further investigation into the risks and benefits of not fasting before cardiac catheterisation is warranted.
Conclusion
This is the first systematic review to synthesise evidence about not fasting before coronary angiography and angioplasty. It has revealed limited evidence regarding this practice. Thematic analysis of nine studies demonstrates that current fasting practices are based on managing perceived risk and that not fasting before angiography is generally considered safe and beneficial for the patient. Due to the gap in knowledge that exists regarding this topic, there is significant potential for future research, both locally and internationally. Future multi-centre randomised controlled trials will build a reliable and robust knowledge base on this topic. It appears that the ongoing concerns around not fasting are related to perceived risk, rather than actual risk. However, further research is needed in this area to support policy and practice change on a large scale.
Summary
Historically, patients undergoing cardiac catheterisation have not been allowed to eat or drink for at least six hours prior to their procedure. Fasting in this context has recently been questioned by scholars around the world. This literature review has shown that being able to eat and drink in the lead up to this procedure is considered safe and beneficial for the patient. However, guidelines and practices are inconsistent and further research needs to be done to encourage hospitals around New Zealand and across the world to change their practice.
Abstract
Aim
To synthesise international evidence about not fasting before cardiac catheterisation.
Method
We used a systematic, integrative literature review and applied quality assessment criteria.
Results
Nine of 1,535 articles met the inclusion criteria. Critique and analysis of the literature revealed three themes: (1) Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management. (2) Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting. (3) Current practice, evidence and guidelines are inconsistent.
Conclusion
Ongoing concerns regarding not fasting before cardiac catheterisation are related to perceived risk, not actual risk. Indeed, this review indicates that not fasting may optimise patient experience. Further large-scale research is needed in this area to support policy and practice change to a patient-centric fasting protocol.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
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Is not fasting before cardiac catheterisation better than fasting? A systematic integrative literature review
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Coronary artery disease (CAD) is the leading cause of death internationally and the second leading cause of death in New Zealand.[[1,2]] The disease carries a significant health burden and affects more than 170,000 individuals across New Zealand.[[3]] Cardiac catheterisation is the gold standard test for diagnosis of coronary artery disease.[[4]] This procedure is minimally invasive and usually completed under conscious sedation. In recent years, the risks associated with this procedure have decreased substantially due to the development of equipment, peri-procedural care and operator experience.[[5]] Accordingly, diagnostic angiography is commonly completed as an outpatient procedure, with many elective angioplasties following the same trend.[[6]]
Historically, patients undergoing coronary angiography and angioplasty have been required to fast in preparation for this procedure.[[7,8]] However, scholars have questioned the evidence base for this practice, with some centres changing guidelines to remove fasting altogether.[[9,10]] Concerns regarding eating before procedures relate to the possible increased risk for pulmonary aspiration, a serious event that can lead to pneumonia, respiratory compromise and death.[[11,12]] However, fasting patients for an extended period could put patients at higher risk of other complications, including hypotension, contrast-induced nephropathy and hypoglycaemia.[[5,13]] Allowing patients to eat and drink before coronary angiography positively affects the individual’s experience, improves patient satisfaction and reduces anxiety.[[14–16]] In this context, we aimed to synthesise current international evidence about not fasting before cardiac catheterisation.
Methods
We used an integrative review to synthesise current evidence about not fasting before coronary angiography and angioplasty. The integrative method is the broadest type of review, allowing the inclusion of studies with diverse methodologies, including both empirical and theoretical publications.[[17,18]] This systematic approach facilitates an in-depth analysis and captures varied perspectives on a topic without the focus on hierarchical evidence types.[[17,18]]
Searches were carried out via title, subject and keyword using the following online databases: MEDLINE, Scopus, the Cumulative Index to Nursing and Allied Health Literature (CINAHL Plus), Cochrane and Web of Science. The search terms listed in Table 1 captured variations of the terms “non-fasted,” “fasted,” “before,” “coronary angiography” and “coronary angioplasty.” Terms were combined using Boolean operators. Inclusion and exclusion criteria are listed in Table 2.
The initial search yielded 1,531 papers. After the removal of duplicates and screening by title and abstract, seven studies remained and were screened by full text. Four papers were added through reference checking and screened. Of these 11, nine studies were included in the review (Figure 1).
Table 1: Search terms.
Table 2: Inclusion and exclusion criteria.
Figure 1: Flowchart of literature selection process.
Data extraction was completed using a standard pro forma and included: relevance to the research question, study design and limitations.[[19]] Studies were then assessed for quality and methodological rigour (Table 3). For research reviews, no gold standard for quality scores exists; the diversity of methodologies means criteria for quality assessment are variable.[[17]] We chose the quantitative assessment tool developed by Hawker et al[[20]] to assess empirical studies and abstracts. This tool evaluates each section of the study, including abstract, research aims and background, methodology and sampling, data collection and analysis, ethics and bias and research findings. Overall, the quality of available evidence was low. The quality of evidence published by Hamid et al[[9]] and Bacus et al[[14]] were rated as fair. The abstracts from Mishra et al[[15]] and Li et al[[21]] were rated as poor as they did not provide sufficient information to accurately assess some article sections using the evaluation tool. The opinion pieces, study protocols and nursing guidelines were considered grey literature and were not formally scored for quality.[[22]]
The process of thematic data analysis followed the six-phase approach outlined by Braun and Clarke: familiarisation with data, generating initial codes, searching for themes, reviewing themes, defining and naming themes and producing the report.[[23]] Data from all studies were extracted and coded. Codes were catalogued and grouped in Microsoft Excel to allow for identification of themes. This theme-based approach to data extraction allowed information from a variety of sources to be compared and combined.[[24]]
Table 3: Evidence on not fasting before cardiac catheterisation. View Table 3.
Results
Of the nine studies included in this review, there was one retrospective observational analysis of a data registry,[[9]] one prospective observational study[[14]] and two abstracts of randomised controlled trials from conference proceedings.[[15,21]] There were three opinion pieces (two of which provided commentary on other studies included in this review),[[16,26,27]] one published clinical guideline[[28]] and one record from a clinical trials register.[[25]] Three studies discussed both coronary angiography and angioplasty[[14,21,25]] and five studies discussed coronary angioplasty only.[[9,16,26–28]] One study did not outline whether included participants underwent coronary angiography or angioplasty.[[15]] Seven studies commented on the incidence of outcomes associated with fasting or not fasting.[[9,14–16,21,25,26]] Of the four empirical studies, one was completed in the United Kingdom,[[9]] one in New Zealand,[[14]] one in Singapore[[21]] and one in the United States of America.[[15]] The planned study, found on the clinical trial registry, will be completed in the United Kingdom.[[25]]
Two full-text empirical studies were identified, one with 1916 participants involved[[9]] and the second with 1,030 participants.[[14]] Abdelaziz[[25]] has indicated an intention to complete a randomised controlled trial involving 600 participants. Their study outline hypothesises that there will be no difference in the incidence of procedural complications between non-fasted and fasted groups and that the non-fasted groups will have a lower incidence of hypoglycaemia and hypotension.[[25]] This is similar to Hamid et al[[9]] and Li et al,[[21]] who aimed to show the safety of not fasting before coronary angiography and angioplasty. Three studies concluded that their results demonstrated the safety of this practice.[[9,15,21]]
Thematic analysis identified the following three themes related to not fasting before cardiac catheterisation:
- Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management.
- Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting.
- Current practice, evidence and guidelines are inconsistent and further study is required.
Theme 1: fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management
The benefits of fasting found in this literature search are centred around mitigating the possible risks associated with not fasting. Fasting is thought to reduce the risk of vomiting, bronchial aspiration and resulting pneumonia.[[9,14,26]] However, Hamid et al[[16]] suggest that the increased risk of aspiration in unfasted patients is unfounded. There is also a perceived benefit of fasting due to the possibility of proceeding to emergency surgery and the need for general anaesthesia.[[9,28]] For this reason, patients routinely fast from four to eight hours before coronary angiography.[[9,14,26]] Hamid et al[[9]] claim that the benefits of fasting before coronary angiography and angioplasty are not evidence-based, as little evidence exists. Hamid et al[[16]] suggest that the risk associated with not fasting has been overstated and that those who fast may be at greater risk of complications. Interestingly, individuals presenting with an acute requirement for angioplasty did not fast before the procedure.[[16]] Further, there are limited reports of excess peri-procedural pulmonary aspiration or related complications during emergency coronary artery bypass grafting in the unfasted patient.[[16,25]]
Theme 2: not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting
Coronary angiography is considered a safe procedure, which brings into question the need for fasting in preparation.[[26]] In one study involving 1,916 angioplasty patients over three years, only two patients (0.1%) required subsequent emergency coronary artery bypass grafting surgery.[[9]] Also, none of the patients in this population fasted, and yet none required intubation during the angioplasty procedure and there were no episodes of aspiration pneumonia. Similarly, Bacus et al[[14]] reported that, among 1,030 elective coronary angiography and angioplasty patients, there were no episodes of aspiration. Mishra et al[[15]] recorded one episode of aspiration pneumonitis in the non-fasting group of 253 inpatients, and this did not represent a statistically significant difference between the non-fasting and fasting groups. The outcomes of small-scale studies demonstrate that reducing or eliminating fasting before coronary angiography and angioplasty may be safe. However, further studies are needed to explore this.[[9,21,26]]
The benefits of not fasting before cardiac catheterisation are mostly perceived rather than evidence-based. Scholars hypothesise that allowing patients to eat and drink up to the time of their procedure will increase their level of hydration, reduce the risk of contrast-induced nephropathy, improve vascular access and reduce peri-procedural hypotension and hypoglycaemia.[[9,14,16,21]] Fasting-related procedural delay and cancellation is thought to significantly impact patients and optimal health resource allocation.[[14]] These delays can be avoided, and hospital stays potentially shortened, if patients are allowed to eat pre-procedure.[[9,16,25]] Scholars also predict that non-fasting patients may be less anxious before their procedure.[[16]] Following preliminary analysis, Mishra et al[[15]] reported that non-fasting patients had a significantly higher patient satisfaction score and a lower cost of index hospitalisation compared to the fasting group.
Pre-procedural fasting is associated with risk and possible complications. In a randomised trial, patients that were allowed to eat up to two hours before angiography had a lower incidence of hypotension requiring a fluid bolus (4% vs 9.4%) and a lower incidence of nausea (0% vs 0.8%) when compared to those who had fasted overnight.[[21]] However, patients that were fasted for less time also required a larger dose of sedation (6.8% vs 2.6%) as a result of anxiety or arterial spasm.[[21]] Mishra et al[[15]] compared patients who fasted solids from midnight and clear fluids from two hours before the procedure to patients who were allowed to eat and drink until the time of the procedure. There was no statistically significant difference between the two groups for incidence of adverse events, such as peri-procedural hypotension, contrast-induced nephropathy, hypoglycaemia, hyperglycaemia, nausea, vomiting and 30-day mortality. In the study completed by Bacus et al[[14]] , 47% of patients with a mean fasting time of 11.6 hours reported feeling hungry, and 11.6% reported headaches. Prolonged periods of fasting is thought to increase insulin resistance, potentially exacerbating the metabolic response following trauma.[[16]] Additionally, patients who are fasting may be less likely to take their morning medication, including anti-hypertensives, leading to poorly controlled hypertension.[[9]] Bacus et al[[14]] reported eight episodes of hyperglycaemia and seven episodes of hypoglycaemia, suggesting that this may have been due to missed medications and prolonged fasting. Fasted individuals, particularly the older age group, are at risk of dehydration, hypoglycaemia and contrast-induced nephropathy.[[9,26]] Such complications could lead to a prolonged hospital stay with economic and health implications.[[9]]
Theme 3: current practice, evidence and guidelines are inconsistent and further study is required
Data available in this review indicate there is an inconsistency in practices between institutions. In New Zealand, one hospital guideline recommended fasting patients for four to six hours.[[14]] The practice in two district general hospitals in the United Kingdom was that no patients were fasted in preparation for cardiac catheterisation.[[9]] In Singapore, standard practice in one hospital was to fast patients from midnight for both elective and in-hospital cardiac catheterisation.[[21]] The duration of fasting within a New Zealand institution was variable, with patients fasting anywhere between zero and 24 hours before their procedure.[[14]] The mean fasting time of 11.6 hours was greater than anticipated considering the maximum recommended duration for fasting was six hours.[[14]] In emergencies, however, angioplasty is performed urgently without any fasting restrictions.[[9,26]] Current practice in this context is based on limited scientific evidence and may have developed from fasting guidelines for general anaesthesia.[[9,14,16,25–27]] According to Wijeyeratne et al,[[27]] the evidence base relating to this practice and the optimal period of fasting has been “exceedingly slow to develop.”
Authors of papers included in this review claim that there are no available fasting guidelines specific to coronary angiography and angioplasty.[[9,16,26]] Instead, information and opinion identified in this review suggest that practice is based on local hospital and health board guidelines, which are considered inconsistent and unsubstantiated.[[9,25,27,28]] Protocols and guidelines such as this require revision.[[26]] Clinical nursing guidelines for angioplasty published in 2011 state that, given the available evidence, routine fasting for coronary angioplasty “is not justifiable; fasting should be based on clinical judgement on a case-by-case basis.”[[28]] However, the grade of this recommendation was documented as low, and consensus among the panel of clinical experts had not been reached. Clinicians are encouraged to “follow local policy and procedures.”[[28]]
Although both Hamid et al[[9]] and Mishra et al[[15]] suggest that their research demonstrates patients do not require fasting before coronary angioplasty, this review identified that there is consensus on the need for further study.[[9,16,21,26,27]] Future research should involve larger cohorts and multiple centres in randomised controlled trials in order to support interventional cardiologists to change from their current practice.[[ 9,16,21,26,27]] Studies currently underway aim to record the incidence of outcomes related to fasting and not fasting, such as contrast-induced nephropathy, hypotension, nausea, vomiting, emergency intubation, aspiration pneumonia, hyperglycaemia, hypoglycaemia and patient satisfaction.[[15,25]]
Discussion
Overall, analysis of the nine papers in this review identified limited evidence about not fasting before cardiac catheterisation. Thematic synthesis revealed that, although not fasting in this context is generally considered to be safe, there is still concern with implementing this practice in a clinical setting. This review identified that the potential for vomiting and pulmonary aspiration are two significant concerns associated with not fasting before coronary angiography and angioplasty. Vomiting, nausea and allergic reactions were once common complications of angiography due to the hypertonic nature of first-generation contrast dye.[[29]] In some reports, reactions to contrast dye occurred in over 50% of cases.[[30]] Such reactions could be why fasting was once a relevant choice for cardiac catheterisation. However, contrast dye used today is low-osmolality and non-ionic, and the reported rate of vomiting is low (0.8%).[[5]] Similarly, the risk of requiring emergency surgery has reduced significantly in recent years and is reported at around 0.14% in the contemporary setting.[[31]] These diminishing risks question the necessity of this practice.[[14]]
Although there is limited recent evidence to support fasting in this context, this practice continues to be widely enforced and supported by healthcare professionals. The recommendation of fasting before cardiac catheterisation is based on perceived risk, and it does not acknowledge the potential risk associated with fasting. It may be that physicians are more concerned by rare events with potentially severe outcomes than the possibility of more common adverse events with lesser effects from not fasting. For example, the perceived risk of aspiration causing serious harm for a small number of individuals may be over-emphasised in the context of the general wellbeing and comfort of the majority of patients. Although this is understandable, it limits the opportunity to foster the potential safe and beneficial outcomes of not fasting in this context. Indeed, in the randomised controlled trial by Mishra et al,[[15]] unfasted patients reported higher satisfaction scores following cardiac catheterisation compared to those who fasted.
Research in other fields does not show a connection between not fasting and vomiting or aspiration when patients receive conscious sedation. In a study of cerebral angiography by Kwon et al,[[32]] there was no statistical difference in nausea and vomiting between fasting and non-fasting groups, and there were no cases of pulmonary aspiration among 2,554 patients. The overall incidence of nausea and vomiting was low, reported at 1.05%. Similarly, a systematic review of various procedures involving conscious sedation found no episodes of aspiration in unfasted patients undergoing procedures other than endoscopy.[[33]] Research regarding procedural sedation in the emergency department has shown no association between fasting duration and the incidence of vomiting and other complications.[[12,34,35]] Indeed, current recommendations for conscious sedation in the emergency department state that fasting is not required when verbal contact is maintained.[[36]]
The overall quality of evidence included in the review was assessed as poor when compared to empirical evidence, as it is based predominantly on expert opinion.[[22,37]] However, the quality of grey literature is variable, and its inclusion can be important in reducing publication bias and providing contextual factors.[[38]] The low quality of evidence identified by this review limits understanding of the safety of not fasting and its future utility. Further, there is no consensus among experts for recommendations in this area and practice varies greatly between and within hospitals.[[9,14,21,25,26,28]] Indeed, current guidelines and local practices may not be based on scientific evidence. We argue that further investigation into the risks and benefits of not fasting before cardiac catheterisation is warranted.
Conclusion
This is the first systematic review to synthesise evidence about not fasting before coronary angiography and angioplasty. It has revealed limited evidence regarding this practice. Thematic analysis of nine studies demonstrates that current fasting practices are based on managing perceived risk and that not fasting before angiography is generally considered safe and beneficial for the patient. Due to the gap in knowledge that exists regarding this topic, there is significant potential for future research, both locally and internationally. Future multi-centre randomised controlled trials will build a reliable and robust knowledge base on this topic. It appears that the ongoing concerns around not fasting are related to perceived risk, rather than actual risk. However, further research is needed in this area to support policy and practice change on a large scale.
Summary
Historically, patients undergoing cardiac catheterisation have not been allowed to eat or drink for at least six hours prior to their procedure. Fasting in this context has recently been questioned by scholars around the world. This literature review has shown that being able to eat and drink in the lead up to this procedure is considered safe and beneficial for the patient. However, guidelines and practices are inconsistent and further research needs to be done to encourage hospitals around New Zealand and across the world to change their practice.
Abstract
Aim
To synthesise international evidence about not fasting before cardiac catheterisation.
Method
We used a systematic, integrative literature review and applied quality assessment criteria.
Results
Nine of 1,535 articles met the inclusion criteria. Critique and analysis of the literature revealed three themes: (1) Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management. (2) Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting. (3) Current practice, evidence and guidelines are inconsistent.
Conclusion
Ongoing concerns regarding not fasting before cardiac catheterisation are related to perceived risk, not actual risk. Indeed, this review indicates that not fasting may optimise patient experience. Further large-scale research is needed in this area to support policy and practice change to a patient-centric fasting protocol.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
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5) Tavakol M, Ashraf S, Brener SJ. Risks and complications of coronary angiography: A comprehensive review. Glob J Health Sci. 2012;4:65-93.
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8) Grossman W. Grossman's cardiac catheterization, angiography, and intervention. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.
9) Hamid T, Aleem Q, Lau Y, et al. Pre-procedural fasting for coronary interventions: Is it time to change practice? Heart. 2014;100:658-61.
10) Kern M. Should NPO be the rule before cath? Reexamining pre-procedure routines. Cath Lab Digest 2010;18 [cited 2020 Nov 7]. Available from: https://www.cathlabdigest.com/articles/Should-NPO-Be-Rule-Cath-Reexamining-Pre-Procedure-Routines#:~:text=Reexamining%20Pre%2DProcedure%20Routines,-Issue%20Number&text=There%20are%20many%20tests%20and,several%20hours%20before%20the%20procedure
11) American Society of Anesthesiologists Committee on Standards and Practice Parameters. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures: An updated report by the American Society of Anesthesiologists Task Force on preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration. Anesthesiology. 2017;126:376-93.
12) Thorpe RJ, Benger J. Pre-procedural fasting in emergency sedation. Emerg Med J. 2010;27:254-61.
13) Hiremath S, Akbari A, Shabana W, et al. Prevention of contrast-induced acute kidney injury: Is simple oral hydration similar to intravenous? A systematic review of the evidence. PLOS ONE. 2013;8:Article e60009.
14) Bacus S, Parsons J, Benatar J, et al. Fasting prior to cardiac catheterisation: A single-centre observational study. NZ Med J. 2020;133:16-22. Available from: https://www.nzma.org.nz/journal-articles/fasting-prior-to-cardiac-catheterisation-a-single-centre-observational-study
15) Mishra A, Kane M, Acker W, et al. Can we safely have our patients eat with cardiac catheterization-nix or allow: The chow now study (preliminary analysis from inpatient population). Catheter Cardiovasc Interv. 2019;93:S248‐S9.
16) Hamid T, Macdonald JE, Balachandran KP, Mudawi T. Re: Preprocedural fasting for coronary interventions: Is it time to change practice? The authors' reply [letter]. Heart. 2014;100:1988.
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20) Hawker S, Payne S, Kerr C, et al. Appraising the evidence: Reviewing disparate data systematically. Qual Health Res. 2002;12:1284-99.
21) Li Y, Latt TZ, Tan C, et al. Routine cardiac catheterization is safe in non-fasted patients. J Am Coll Cardiol. 2017;69:S58-S9.
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23) Braun V, Clarke V. Using thematic analysis in psychology. Qual Res Psychol. 2006;3:77-101.
24) Dixon-Woods M, Agarwal S, Jones D, et al. Synthesising qualitative and quantitative evidence: A review of possible methods. J Health Serv Res Policy. 2005;10:45-53.
25) Abdelaziz H. Fasting or non fasting for cardiac catheterization. 2018. ClinicalTrials.gov registration number: NCT03555500
26) Aguilar-Nascimento JE, Feguri GR. Fasting may not be required before percutaneous coronary intervention. Evid-Based Nurs. 2015;18:41.
27) Wijeyeratne YD, Wendler R, Spray D, Bunce N. Preprocedural fasting for coronary interventions: Is it time to change practice? Heart. 2014;100:1065.
28) Rolley JX, Salamonson Y, Wensley C, et al. Nursing clinical practice guidelines to improve care for people undergoing percutaneous coronary interventions. Aust Crit Care. 2011;24:18-38.
29) Barrett BJ, Parfrey PS, Vavasour HM, et al. A comparison of nonionic, low-osmolality radiocontrast agents with ionic, high-osmolality agents during cardiac catheterization. New Engl J Med. 1992;326:431-6.
30) Matthai WH, Jr., Kussmaul WG, III., Krol J, et al. A comparison of low-with high-osmolality contrast agents in cardiac angiography: Identification of criteria for selective use. Circ J. 1994;89:291-301.
31) Seshadri, N., Whitlow, P. L., Acharya, N., et al. Emergency coronary artery bypass surgery in the contemporary percutaneous coronary intervention era. Circ J. 2002;106:2346-50.
32) Kwon OK, Oh CW, Park H, et al. Is fasting necessary for elective cerebral angiography? Am J Neuroradiol. 2011;32:908-10.
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35) Wenzel-Smith G, Schweitzer B. Safety and efficacy of procedural sedation and analgesia (PSA) conducted by medical officers in a level 1 hospital in Cape Town. S Afr Med J. 2011;101:895-8. Available from: https://www.ajol.info/index.php/samj/article/view/73473
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Contact diana@nzma.org.nz
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Is not fasting before cardiac catheterisation better than fasting? A systematic integrative literature review
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Coronary artery disease (CAD) is the leading cause of death internationally and the second leading cause of death in New Zealand.[[1,2]] The disease carries a significant health burden and affects more than 170,000 individuals across New Zealand.[[3]] Cardiac catheterisation is the gold standard test for diagnosis of coronary artery disease.[[4]] This procedure is minimally invasive and usually completed under conscious sedation. In recent years, the risks associated with this procedure have decreased substantially due to the development of equipment, peri-procedural care and operator experience.[[5]] Accordingly, diagnostic angiography is commonly completed as an outpatient procedure, with many elective angioplasties following the same trend.[[6]]
Historically, patients undergoing coronary angiography and angioplasty have been required to fast in preparation for this procedure.[[7,8]] However, scholars have questioned the evidence base for this practice, with some centres changing guidelines to remove fasting altogether.[[9,10]] Concerns regarding eating before procedures relate to the possible increased risk for pulmonary aspiration, a serious event that can lead to pneumonia, respiratory compromise and death.[[11,12]] However, fasting patients for an extended period could put patients at higher risk of other complications, including hypotension, contrast-induced nephropathy and hypoglycaemia.[[5,13]] Allowing patients to eat and drink before coronary angiography positively affects the individual’s experience, improves patient satisfaction and reduces anxiety.[[14–16]] In this context, we aimed to synthesise current international evidence about not fasting before cardiac catheterisation.
Methods
We used an integrative review to synthesise current evidence about not fasting before coronary angiography and angioplasty. The integrative method is the broadest type of review, allowing the inclusion of studies with diverse methodologies, including both empirical and theoretical publications.[[17,18]] This systematic approach facilitates an in-depth analysis and captures varied perspectives on a topic without the focus on hierarchical evidence types.[[17,18]]
Searches were carried out via title, subject and keyword using the following online databases: MEDLINE, Scopus, the Cumulative Index to Nursing and Allied Health Literature (CINAHL Plus), Cochrane and Web of Science. The search terms listed in Table 1 captured variations of the terms “non-fasted,” “fasted,” “before,” “coronary angiography” and “coronary angioplasty.” Terms were combined using Boolean operators. Inclusion and exclusion criteria are listed in Table 2.
The initial search yielded 1,531 papers. After the removal of duplicates and screening by title and abstract, seven studies remained and were screened by full text. Four papers were added through reference checking and screened. Of these 11, nine studies were included in the review (Figure 1).
Table 1: Search terms.
Table 2: Inclusion and exclusion criteria.
Figure 1: Flowchart of literature selection process.
Data extraction was completed using a standard pro forma and included: relevance to the research question, study design and limitations.[[19]] Studies were then assessed for quality and methodological rigour (Table 3). For research reviews, no gold standard for quality scores exists; the diversity of methodologies means criteria for quality assessment are variable.[[17]] We chose the quantitative assessment tool developed by Hawker et al[[20]] to assess empirical studies and abstracts. This tool evaluates each section of the study, including abstract, research aims and background, methodology and sampling, data collection and analysis, ethics and bias and research findings. Overall, the quality of available evidence was low. The quality of evidence published by Hamid et al[[9]] and Bacus et al[[14]] were rated as fair. The abstracts from Mishra et al[[15]] and Li et al[[21]] were rated as poor as they did not provide sufficient information to accurately assess some article sections using the evaluation tool. The opinion pieces, study protocols and nursing guidelines were considered grey literature and were not formally scored for quality.[[22]]
The process of thematic data analysis followed the six-phase approach outlined by Braun and Clarke: familiarisation with data, generating initial codes, searching for themes, reviewing themes, defining and naming themes and producing the report.[[23]] Data from all studies were extracted and coded. Codes were catalogued and grouped in Microsoft Excel to allow for identification of themes. This theme-based approach to data extraction allowed information from a variety of sources to be compared and combined.[[24]]
Table 3: Evidence on not fasting before cardiac catheterisation. View Table 3.
Results
Of the nine studies included in this review, there was one retrospective observational analysis of a data registry,[[9]] one prospective observational study[[14]] and two abstracts of randomised controlled trials from conference proceedings.[[15,21]] There were three opinion pieces (two of which provided commentary on other studies included in this review),[[16,26,27]] one published clinical guideline[[28]] and one record from a clinical trials register.[[25]] Three studies discussed both coronary angiography and angioplasty[[14,21,25]] and five studies discussed coronary angioplasty only.[[9,16,26–28]] One study did not outline whether included participants underwent coronary angiography or angioplasty.[[15]] Seven studies commented on the incidence of outcomes associated with fasting or not fasting.[[9,14–16,21,25,26]] Of the four empirical studies, one was completed in the United Kingdom,[[9]] one in New Zealand,[[14]] one in Singapore[[21]] and one in the United States of America.[[15]] The planned study, found on the clinical trial registry, will be completed in the United Kingdom.[[25]]
Two full-text empirical studies were identified, one with 1916 participants involved[[9]] and the second with 1,030 participants.[[14]] Abdelaziz[[25]] has indicated an intention to complete a randomised controlled trial involving 600 participants. Their study outline hypothesises that there will be no difference in the incidence of procedural complications between non-fasted and fasted groups and that the non-fasted groups will have a lower incidence of hypoglycaemia and hypotension.[[25]] This is similar to Hamid et al[[9]] and Li et al,[[21]] who aimed to show the safety of not fasting before coronary angiography and angioplasty. Three studies concluded that their results demonstrated the safety of this practice.[[9,15,21]]
Thematic analysis identified the following three themes related to not fasting before cardiac catheterisation:
- Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management.
- Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting.
- Current practice, evidence and guidelines are inconsistent and further study is required.
Theme 1: fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management
The benefits of fasting found in this literature search are centred around mitigating the possible risks associated with not fasting. Fasting is thought to reduce the risk of vomiting, bronchial aspiration and resulting pneumonia.[[9,14,26]] However, Hamid et al[[16]] suggest that the increased risk of aspiration in unfasted patients is unfounded. There is also a perceived benefit of fasting due to the possibility of proceeding to emergency surgery and the need for general anaesthesia.[[9,28]] For this reason, patients routinely fast from four to eight hours before coronary angiography.[[9,14,26]] Hamid et al[[9]] claim that the benefits of fasting before coronary angiography and angioplasty are not evidence-based, as little evidence exists. Hamid et al[[16]] suggest that the risk associated with not fasting has been overstated and that those who fast may be at greater risk of complications. Interestingly, individuals presenting with an acute requirement for angioplasty did not fast before the procedure.[[16]] Further, there are limited reports of excess peri-procedural pulmonary aspiration or related complications during emergency coronary artery bypass grafting in the unfasted patient.[[16,25]]
Theme 2: not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting
Coronary angiography is considered a safe procedure, which brings into question the need for fasting in preparation.[[26]] In one study involving 1,916 angioplasty patients over three years, only two patients (0.1%) required subsequent emergency coronary artery bypass grafting surgery.[[9]] Also, none of the patients in this population fasted, and yet none required intubation during the angioplasty procedure and there were no episodes of aspiration pneumonia. Similarly, Bacus et al[[14]] reported that, among 1,030 elective coronary angiography and angioplasty patients, there were no episodes of aspiration. Mishra et al[[15]] recorded one episode of aspiration pneumonitis in the non-fasting group of 253 inpatients, and this did not represent a statistically significant difference between the non-fasting and fasting groups. The outcomes of small-scale studies demonstrate that reducing or eliminating fasting before coronary angiography and angioplasty may be safe. However, further studies are needed to explore this.[[9,21,26]]
The benefits of not fasting before cardiac catheterisation are mostly perceived rather than evidence-based. Scholars hypothesise that allowing patients to eat and drink up to the time of their procedure will increase their level of hydration, reduce the risk of contrast-induced nephropathy, improve vascular access and reduce peri-procedural hypotension and hypoglycaemia.[[9,14,16,21]] Fasting-related procedural delay and cancellation is thought to significantly impact patients and optimal health resource allocation.[[14]] These delays can be avoided, and hospital stays potentially shortened, if patients are allowed to eat pre-procedure.[[9,16,25]] Scholars also predict that non-fasting patients may be less anxious before their procedure.[[16]] Following preliminary analysis, Mishra et al[[15]] reported that non-fasting patients had a significantly higher patient satisfaction score and a lower cost of index hospitalisation compared to the fasting group.
Pre-procedural fasting is associated with risk and possible complications. In a randomised trial, patients that were allowed to eat up to two hours before angiography had a lower incidence of hypotension requiring a fluid bolus (4% vs 9.4%) and a lower incidence of nausea (0% vs 0.8%) when compared to those who had fasted overnight.[[21]] However, patients that were fasted for less time also required a larger dose of sedation (6.8% vs 2.6%) as a result of anxiety or arterial spasm.[[21]] Mishra et al[[15]] compared patients who fasted solids from midnight and clear fluids from two hours before the procedure to patients who were allowed to eat and drink until the time of the procedure. There was no statistically significant difference between the two groups for incidence of adverse events, such as peri-procedural hypotension, contrast-induced nephropathy, hypoglycaemia, hyperglycaemia, nausea, vomiting and 30-day mortality. In the study completed by Bacus et al[[14]] , 47% of patients with a mean fasting time of 11.6 hours reported feeling hungry, and 11.6% reported headaches. Prolonged periods of fasting is thought to increase insulin resistance, potentially exacerbating the metabolic response following trauma.[[16]] Additionally, patients who are fasting may be less likely to take their morning medication, including anti-hypertensives, leading to poorly controlled hypertension.[[9]] Bacus et al[[14]] reported eight episodes of hyperglycaemia and seven episodes of hypoglycaemia, suggesting that this may have been due to missed medications and prolonged fasting. Fasted individuals, particularly the older age group, are at risk of dehydration, hypoglycaemia and contrast-induced nephropathy.[[9,26]] Such complications could lead to a prolonged hospital stay with economic and health implications.[[9]]
Theme 3: current practice, evidence and guidelines are inconsistent and further study is required
Data available in this review indicate there is an inconsistency in practices between institutions. In New Zealand, one hospital guideline recommended fasting patients for four to six hours.[[14]] The practice in two district general hospitals in the United Kingdom was that no patients were fasted in preparation for cardiac catheterisation.[[9]] In Singapore, standard practice in one hospital was to fast patients from midnight for both elective and in-hospital cardiac catheterisation.[[21]] The duration of fasting within a New Zealand institution was variable, with patients fasting anywhere between zero and 24 hours before their procedure.[[14]] The mean fasting time of 11.6 hours was greater than anticipated considering the maximum recommended duration for fasting was six hours.[[14]] In emergencies, however, angioplasty is performed urgently without any fasting restrictions.[[9,26]] Current practice in this context is based on limited scientific evidence and may have developed from fasting guidelines for general anaesthesia.[[9,14,16,25–27]] According to Wijeyeratne et al,[[27]] the evidence base relating to this practice and the optimal period of fasting has been “exceedingly slow to develop.”
Authors of papers included in this review claim that there are no available fasting guidelines specific to coronary angiography and angioplasty.[[9,16,26]] Instead, information and opinion identified in this review suggest that practice is based on local hospital and health board guidelines, which are considered inconsistent and unsubstantiated.[[9,25,27,28]] Protocols and guidelines such as this require revision.[[26]] Clinical nursing guidelines for angioplasty published in 2011 state that, given the available evidence, routine fasting for coronary angioplasty “is not justifiable; fasting should be based on clinical judgement on a case-by-case basis.”[[28]] However, the grade of this recommendation was documented as low, and consensus among the panel of clinical experts had not been reached. Clinicians are encouraged to “follow local policy and procedures.”[[28]]
Although both Hamid et al[[9]] and Mishra et al[[15]] suggest that their research demonstrates patients do not require fasting before coronary angioplasty, this review identified that there is consensus on the need for further study.[[9,16,21,26,27]] Future research should involve larger cohorts and multiple centres in randomised controlled trials in order to support interventional cardiologists to change from their current practice.[[ 9,16,21,26,27]] Studies currently underway aim to record the incidence of outcomes related to fasting and not fasting, such as contrast-induced nephropathy, hypotension, nausea, vomiting, emergency intubation, aspiration pneumonia, hyperglycaemia, hypoglycaemia and patient satisfaction.[[15,25]]
Discussion
Overall, analysis of the nine papers in this review identified limited evidence about not fasting before cardiac catheterisation. Thematic synthesis revealed that, although not fasting in this context is generally considered to be safe, there is still concern with implementing this practice in a clinical setting. This review identified that the potential for vomiting and pulmonary aspiration are two significant concerns associated with not fasting before coronary angiography and angioplasty. Vomiting, nausea and allergic reactions were once common complications of angiography due to the hypertonic nature of first-generation contrast dye.[[29]] In some reports, reactions to contrast dye occurred in over 50% of cases.[[30]] Such reactions could be why fasting was once a relevant choice for cardiac catheterisation. However, contrast dye used today is low-osmolality and non-ionic, and the reported rate of vomiting is low (0.8%).[[5]] Similarly, the risk of requiring emergency surgery has reduced significantly in recent years and is reported at around 0.14% in the contemporary setting.[[31]] These diminishing risks question the necessity of this practice.[[14]]
Although there is limited recent evidence to support fasting in this context, this practice continues to be widely enforced and supported by healthcare professionals. The recommendation of fasting before cardiac catheterisation is based on perceived risk, and it does not acknowledge the potential risk associated with fasting. It may be that physicians are more concerned by rare events with potentially severe outcomes than the possibility of more common adverse events with lesser effects from not fasting. For example, the perceived risk of aspiration causing serious harm for a small number of individuals may be over-emphasised in the context of the general wellbeing and comfort of the majority of patients. Although this is understandable, it limits the opportunity to foster the potential safe and beneficial outcomes of not fasting in this context. Indeed, in the randomised controlled trial by Mishra et al,[[15]] unfasted patients reported higher satisfaction scores following cardiac catheterisation compared to those who fasted.
Research in other fields does not show a connection between not fasting and vomiting or aspiration when patients receive conscious sedation. In a study of cerebral angiography by Kwon et al,[[32]] there was no statistical difference in nausea and vomiting between fasting and non-fasting groups, and there were no cases of pulmonary aspiration among 2,554 patients. The overall incidence of nausea and vomiting was low, reported at 1.05%. Similarly, a systematic review of various procedures involving conscious sedation found no episodes of aspiration in unfasted patients undergoing procedures other than endoscopy.[[33]] Research regarding procedural sedation in the emergency department has shown no association between fasting duration and the incidence of vomiting and other complications.[[12,34,35]] Indeed, current recommendations for conscious sedation in the emergency department state that fasting is not required when verbal contact is maintained.[[36]]
The overall quality of evidence included in the review was assessed as poor when compared to empirical evidence, as it is based predominantly on expert opinion.[[22,37]] However, the quality of grey literature is variable, and its inclusion can be important in reducing publication bias and providing contextual factors.[[38]] The low quality of evidence identified by this review limits understanding of the safety of not fasting and its future utility. Further, there is no consensus among experts for recommendations in this area and practice varies greatly between and within hospitals.[[9,14,21,25,26,28]] Indeed, current guidelines and local practices may not be based on scientific evidence. We argue that further investigation into the risks and benefits of not fasting before cardiac catheterisation is warranted.
Conclusion
This is the first systematic review to synthesise evidence about not fasting before coronary angiography and angioplasty. It has revealed limited evidence regarding this practice. Thematic analysis of nine studies demonstrates that current fasting practices are based on managing perceived risk and that not fasting before angiography is generally considered safe and beneficial for the patient. Due to the gap in knowledge that exists regarding this topic, there is significant potential for future research, both locally and internationally. Future multi-centre randomised controlled trials will build a reliable and robust knowledge base on this topic. It appears that the ongoing concerns around not fasting are related to perceived risk, rather than actual risk. However, further research is needed in this area to support policy and practice change on a large scale.
Summary
Historically, patients undergoing cardiac catheterisation have not been allowed to eat or drink for at least six hours prior to their procedure. Fasting in this context has recently been questioned by scholars around the world. This literature review has shown that being able to eat and drink in the lead up to this procedure is considered safe and beneficial for the patient. However, guidelines and practices are inconsistent and further research needs to be done to encourage hospitals around New Zealand and across the world to change their practice.
Abstract
Aim
To synthesise international evidence about not fasting before cardiac catheterisation.
Method
We used a systematic, integrative literature review and applied quality assessment criteria.
Results
Nine of 1,535 articles met the inclusion criteria. Critique and analysis of the literature revealed three themes: (1) Fasting before coronary angiography and angioplasty is associated with perceived risk management, not actual risk management. (2) Not fasting before coronary angiography and angioplasty is considered safe and beneficial for the patient when compared to the risks of fasting. (3) Current practice, evidence and guidelines are inconsistent.
Conclusion
Ongoing concerns regarding not fasting before cardiac catheterisation are related to perceived risk, not actual risk. Indeed, this review indicates that not fasting may optimise patient experience. Further large-scale research is needed in this area to support policy and practice change to a patient-centric fasting protocol.
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Is not fasting before cardiac catheterisation better than fasting? A systematic integrative literature review
Historically, patients undergoing coronary angiography and angioplasty have been required to fast in preparation for this procedure. However, scholars have questioned the evidence base for this practice, with some centres changing guidelines to remove fasting altogether.
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