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Elective surgery is increasingly common as people live longer and try to maintain their quality of life. The balance between the risks and benefits of an elective operation is an important consideration when deciding whether or not to proceed. The benefits are often relief of pain and increase in function; the risks however, are harder to qualify. There is limited data available and that which we have is often from major public hospitals, which often attract the more complex patients and a heavier workload. The real risk in a community is much harder to define, as many procedures are performed in private hospitals and other smaller public hospitals.In a prospective study of non-cardiac surgical patients aged 70 years or older across Australia and New Zealand, the 30-day mortality was 5%.1 This study is one of only a few that have prospectively analysed surgical outcomes across a wide range of specialties, and it was the largest study of its kind in Australasia. The results however, may not be generalisable to younger patients or patients having surgery at private hospitals, and self-selection of participating hospitals means that they may not be representative of all hospitals in Australasia.The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) is the largest database of postoperative mortality worldwide. It has some limitations, including that large teaching hospitals are overrepresented and studies from it are retrospective in nature. Due to the differences in healthcare delivery in the US compared with Australasia, the data is unlikely to be applicable here. However, an NSQIP study did show a comparable 30-day mortality to the Australasian study.2In New Zealand the Perioperative Mortality Review Committee (POMRC) has the role of providing advice to the Health Quality and Safety commission on how to reduce the number of perioperative deaths. POMRC uses Ministry of Health databases, which have the limitations of coding accuracy and data completeness, and do not include patients that have been treated in private hospitals. POMRC reports have limited use because they are mainly focused on specific procedures.Surgeons and anaesthetists have the important job of informing patients and their families of the risks of any procedure. This can be difficult given the limited contemporary local data available on perioperative mortality. The aim of this study was to determine the mortality after elective surgery at a total community level with inclusion of all patients undergoing elective surgery in Christchurch, New Zealand, forming the largest cohort of elective surgical patients in Australasia and allowing us to describe the mortality of different patient groups within the cohort.MethodThis study was conducted at eight hospitals in Christchurch during November 2014. Hospitals that participated were all Christchurch hospitals where surgery is undertaken (public hospitals: Christchurch Hospital, Christchurch Womens Hospital and Burwood Hospital; and private hospitals: Canterbury Charity Hospital, Christchurch Eye Surgery, Forte Health, St Georges Hospital and Southern Cross Hospital). The University of Otago Human Ethics Committee approved this study and approval was also given by each participating hospital.We studied all patients who underwent elective surgery. Elective surgery was defined as procedures scheduled on a routine elective operating list. Patients were identified for inclusion in the study from operating theatre lists at each hospital. No patients were excluded from the study. For each patient, we collected demographic data, National Health Index (NHI) number, American Society of Anaesthesiologists physical status classification (ASA), type of anaesthetic and surgical specialty. ASA was used as an indicator of preoperative comorbidity. Patients were classified by surgical specialty in a similar way to the Australasian study. For analysis, patients were classified into six age groups: <20 years, 20-34 years, 35-49 years, 50-64 years, 65-79 years and 226580 years, and as either having had a general anaesthetic, sedation or local anaesthetic only.The primary outcome was 30-day mortality defined as death within 30 days after surgery, and the secondary outcome was 90-day mortality defined as death within 90 days after surgery. Dates of deaths were determined by matching NHI numbers with death records held by the Ministry of Health. The clinical records of patients that died were reviewed in order to find the cause of death. A death certificate was obtained where the cause of death could not be determined. The cause of death was classified according to the system used by the Australian and New Zealand College of Anaesthetists (ANZCA) Mortality Working Group, which classifies deaths based on the degree to which the death was anaesthesia-related.3Study data was de-identified. Data was pooled from all hospitals and analysed using computer software (Minitab00ae Release 14.11.1, Minitab Inc, PA, USA and StatView for Windows, Version 5.0.1, SAS Institute Inc, Cary, NC, USA).ResultsFour thousand seven hundred and fifteen patients were identified and included in this study. Two thousand seven hundred and fifty-eight (55%) were female and the median age was 56 years (range 0-99 years) (Table 1). By day 30, 11 (0.2%) patients had died and by day 90, 27 (0.6%) patients had died. Males and females had similar mortality. The highest mortality was in patients aged 80 years or older (30-day mortality 0.8% and 90-day mortality 2.1%). There were no deaths in patients aged younger than 35 years. Mortality did not vary by day of the week of surgery. There was no increase in mortality in patients that underwent surgery on a Friday compared with other days of the week.Table 1:Mortality by sex, ethnicity and age group. n 30-day mortality 90-day mortality Sex Male 2,135 (45%) 7 (0.3%) 13 (0.6%) Female 2,578 (55%) 4 (0.2%) 14 (0.5%) Unknown 2 (0.04%) 0 (0.0%) 0 (0.0%) Ethnicity European 4,105 (87.1%) 8 (0.2%) 24 (0.6%) M1ori 185 (3.9%) 1 (0.5%) 1 (0.5%) Asian 124 (2.6%) 2 (1.6%) 2 (1.6%) Other/Unknown 301 (6.4%) 0 (0.0%) 0 (0.0%) Age group (years) <20 525 (11.1%) 0 (0.0%) 0 (0.0%) 20-34 568 (12.0%) 0 (0.0%) 0 (0.0%) 35-49 816 (17.3%) 1 (0.1%) 1 (0.1%) 50-64 1,268 (26.9%) 2 (0.2%) 4 (0.3%) 65-79 1,150 (24.4%) 5 (0.4%) 14 (1.2%) 226580 384 (8.1%) 3 (0.8%) 8 (2.1%) Unknown 4 (0.1%) 0 (0.0%) 0 (0.0%) Total 4715 11 (0.2%) 27 (0.6%) Values are number (proportion).The majority of patients had a general anaesthetic (3,142 patients, 67%) (Table 2). Patients who had sedation had a higher 30-day and 90-day mortality than patients who had a general anaesthetic or local anaesthetic only. In patients who had a general anaesthetic, 420 patients (13.3%) had severe systemic disease; that is, they were ASA 3 or 4. The 30-day mortality for these patients was 1.0% and the 90-day mortality was 1.9%. For patients that were ASA 1 or 2, the 30-day and 90-day mortality was 0.04% (one death out of 2,722 patients).Table 2: Mortality by type of anaesthetic and ASA (for patients who had a general anaesthetic). Type of anaesthetic n 30-day mortality 90-day mortality General anaesthetic 3,142 (67%) 5 (0.2%) 9 (0.3%) ASA 1 1,457 (30.9%) 0 (0.0%) 0 (0.0%) ASA 2 1,265 (26.8%) 1 (0.1%) 1 (0.1%) ASA 3 401 (8.5%) 2 (0.5%) 5 (1.2%) ASA 4 19 (0.4%) 2 (10.5%) 3 (15.8%) Sedation 628 (13.3%) 4 (0.6%) 12 (1.9%) Local anaesthetic only 727 (15.4%) 1 (0.1%) 5 (0.7%) Unknown 218 (4.6%) 1 (0.5%) 1 (0.5%) Values are number (proportion). ASA 1, a healthy patient with no systemic disease; ASA 2, mild to moderate systemic disease; ASA 3, severe systemic disease imposing functional limitation on patient; ASA 4, severe systemic disease, which is a constant threat to life.When patients who had a general anaesthetic were categorised by age group and ASA, the highest 90-day mortality was patients aged 80 years or older that were ASA 4 (one death out of four patients, 25%) (Table 3). In patients aged 65 to 79 years and ASA 3 or 4, the 30-day mortality was 2.1% and the 90-day mortality was 3.5%, and in patients aged 80 years or older and ASA 3 or 4, the 30-day mortality was 1.2% and the 90-day mortality was 3.7%. There were no deaths of patients aged 65 years or older that were ASA 1 or 2.Table 3: Mortality by age group, type of anaesthetic and ASA (for patients who had a general anaesthetic).Values are number (proportion). ASA 1, a healthy patient with no systemic disease; ASA 2, mild to moderate systemic disease; ASA 3, severe systemic disease imposing functional limitation on patient; ASA 4, severe systemic disease, which is a constant threat to life.The specialty that had the greatest representation in our cohort was endoscopy (948 patients, 20.1%) followed by orthopaedics (814 patients, 17.3%) (Table 4). Specialties that had one or more death were cardiology, cardiothoracic, general, neurosurgery, ophthalmology, plastics, urology, endoscopy and bronchoscopy. Neurosurgery had the highest 30-day mortality of 4.3% (two deaths out of 47 patients) followed by cardiothoracic surgery with a 30-day mortality of 2.4% (two deaths out of 41 patients).Table 4: Mortality by surgical specialty. Surgical specialty n 30-day mortality 90-day mortality Cardiology 64 (1.4%) 1 (1.6%) 1 (1.6%) Cardiothoracic 41 (0.9%) 1 (2.4%) 1 (2.4%) Dental 75 (1.6%) 0 (0.0%) 0 (0.0%) Endocrinology 1 (0.0%) 0 (0.0%) 0 (0.0%) Otolaryngology 358 (7.6%) 0 (0.0%) 0 (0.0%) General 451 (9.6%) 0 (0.0%) 1 (0.2%) Gynaecology 429 (9.1%) 0 (0.0%) 0 (0.0%) Maxilllofacial 28 (0.6%) 0 (0.0%) 0 (0.0%) Neurosurgery 47 (1.0%) 2 (4.3%) 2 (4.3%) Obstetrics 43 (0.9%) 0 (0.0%) 0 (0.0%) Opthalmology 461 (9.8%) 3 (0.7%) 4 (0.9%) Orthopaedics 814 (17.3%) 0 (0.0%) 0 (0.0%) Paediatrics 44 (0.9%) 0 (0.0%) 0 (0.0%) Plastics 477 (10.1%) 0 (0.0%) 4 (0.8%) Urology 164 (3.5%) 0 (0.0%) 1 (0.6%) Vascular 58 (1.2%) 0 (0.0%) 0 (0.0%) Spinal 22 (0.5%) 0 (0.0%) 0 (0.0%) Endoscopy 948 (20.1%) 4 (0.4%) 10 (1.1%) Bronchoscopy 37 (0.8%) 0 (0.0%) 3 (8.1%) Other 153 (3.2%) 0 (0.0%) 0 (0.0%) Values are number (proportion).Of the 27 deaths within 90 days after surgery, one was possibly anaesthesia-related (0.02%). Twenty-two deaths (0.5%) were not anaesthesia-related and the cause of death was unable to be assessed for four patients (0.1%). The one death that was possibly anaesthesia-related occurred in a patient aged 65-79 years who had undergone a neurosurgical procedure under local anaesthetic only.DiscussionIn this prospective observational study of patients undergoing elective surgery in Christchurch we found a 30-day mortality of 0.2% and 90-day mortality of 0.6%. In patients aged 65 years or older the 30-day mortality was 0.5%, and in patients aged 80 years or older the 30-day mortality was 0.8%. These results are not consistent with those of the Australasian study that found a 30-day mortality of 5% in patients aged 70 years or older; however, they are consistent with our expectation that the mortality of patients in our cohort would be lower than that found in the Australasian study.The Australasian study had some limitations that we think may have contributed to a high mortality. Large teaching hospitals were over represented, and no private hospitals were included. Some specialties such as neurosurgery and thoracic surgery may have been over represented because these types of surgery are usually only performed at large teaching hospitals. An NSQIP study reported that thoracic surgery had the highest mortality,2 so patients undergoing thoracic surgery may have disproportionately contributed to the mortality. Patients operated on in public hospitals may have higher preoperative comorbidity, which would mean that the Australasian cohort might have included a disproportionately high number of patients with a high ASA. Our study avoided these limitations by including all patients undergoing any type of surgery at all hospitals. We think that our findings are more likely to reflect the actual situation in New Zealand.Most of the postoperative mortality data that is currently available is from retrospective reviews of administrative databases, and often these are focused on one specific procedure or specialty. One of the largest retrospective observational studies of postoperative mortality showed a postoperative mortality of 1.85% in patients undergoing elective open surgical procedures.4 Our mortality is significantly lower than this. One of the reasons for this may be that we included patients having laparoscopic and diagnostic procedures, which have a lower mortality that open procedures. There are few studies that have prospectively examined mortality across a range of surgical specialties. Most of these studies have used in-hospital mortality as the primary outcome. The first large prospective international study of surgical outcomes showed an in-hospital mortality of 4%.5 Some other older prospective studies of in-hospital mortality have shown similar high mortality rates.6,7 These studies included elective as well as urgent and emergency procedures, which may explain the high mortality. One of the most recent studies to prospectively examine 30-day mortality is a large study performed in the UK, which showed a 30-day mortality for elective surgery of 0.4%.8 Our results are consistent with these findings and the methods of this study were similar to ours. The largest US study to prospectively examine mortality data showed a 30-day mortality of 8% in patients aged 80 years or older and 3% in patients aged less than 80 years.2 These figures are significantly higher than ours, however, the cohort in this study is unlikely to be representative of the whole population because only patients that underwent surgery at Veterans Affairs Medical Centres were included.Advances in perioperative care and minimally invasive surgery have enabled older and sicker patients to have surgery. It is well known that increasing age and ASA are associated with increasing mortality. One study previously mentioned showed that age and comorbidity were independent predictors of 30-day mortality and in patients aged 80 or older ASA was the strongest predictor of mortality.2 Another study showed that patients that are ASA 4 are at 6.75 times the risk of death compared with patients that are ASA 1.5 In our study, 30-day and 90-day mortality increased with each increasing age group and ASA, which is consistent with the findings of other studies.2,5,6,9Sedation is often used as an alternative to general anaesthetic in patients who are considered to be at a too high risk to have a general anaesthetic, so these patients are likely to have high preoperative comorbidity. This may explain the higher mortality of these patients compared with the entire cohort. The high mortality in neurosurgery is likely to be multifactorial but is likely due to the complex nature of neurosurgery as well as the particularly high risk of death of some procedures. For example, in one study previously mentioned, craniotomy for brain tumor had one of the highest mortalities of all procedures at 16.3%.2 The high mortality we saw in cardiothoracic surgery compared with other specialties is consistent with other studies.1,2,4The most recent review of anaesthesia-related mortality by the ANZCA Mortality Working Group showed that over a three-year period, the total number of deaths reported was 1,404, and of these, 112 (8.0%) were considered to be wholly or partly related to anaesthetic factors.3 Deaths included in this review are those that are reported to ANZCA mortality review committees, and these are usually only those that occur within 24-48 hours of an anaesthetic. We used the same system and found that 3.7% of our deaths were anaesthesia-related. Caution should be taken in comparing this figure to that found in the review due to the small numbers of deaths and the differences in the nature of the data. The importance of calculating this figure in our study is to highlight that some postoperative deaths are directly or indirectly related to anaesthesia, and in order to reduce perioperative mortality there must be a system by which all perioperative deaths are reviewed.Number of deaths on the day of surgery and number of in-hospital deaths after surgery are identified in the WHO guidelines for safe surgery 2009 as vital statistics that should be collected on a national level as indicators of performance of a health system. Clearly the WHO considers perioperative mortality data in providing insight into risks associated with surgery. We included both 30-day and 90-day mortality, given we would be able to review all deaths and identify the causes. As expected, the majority were due to progression of the underlying disease and only one was possibly anaesthesia-related.This study has several limitations. Firstly, this data was collected over a one-month period, and this group of patients may not be representative of patients undergoing surgery year round. The data we collected did not allow us to calculate the association between particular comorbidities and mortality, nor particular complications and mortality. The major strength of our study is that it has a large contemporary patient sample with prospective data on all patients, including a wide range of procedures being performed at both public and private hospitals. This is the largest study of this type to have been conducted in Australia and New Zealand.This study provides a unique snapshot of perioperative mortality for patients undergoing elective surgery in Christchurch. We think the results are reassuring in that the mortality rates are similar if not lower than what has been shown in other similar studies. Even though we found what we consider a low mortality rate, this study serves as a reminder of the importance of considering the risks including death of a particular patient undergoing a particular procedure when counseling a patient about elective surgery.

Summary

Abstract

Aim

Most studies assessing mortality after surgery have been undertaken in major public hospitals or are procedure specific. The aim of this study was to determine mortality after elective surgery at a total community level with inclusion of all patients undergoing elective surgery.

Method

This was a prospective study of all patients that underwent elective surgery in Christchurch, New Zealand, within a calendar month. For each patient, we collected demographic data, American Society of Anaesthesiologists physical status classification (ASA), type of anaesthetic and surgical specialty. The primary outcome was 30-day mortality and the secondary outcome was 90-day mortality.

Results

Four thousand seven hundred and fifteen patients were included in this study. Two thousand five hundred and seventy-eight (55%) were female and the median age was 56 years (range 0-99 years). Three thousand one hundred and forty-two (67%) patients had a general anaesthetic. By day 30, 11 (0.2%) patients had died and by day 90, 27 (0.6%) patients had died. Of the 27 deaths within 90 days after surgery, one was possibly anaesthesia-related (0.02%), while the majority were due to progression of disease (18).

Conclusion

This study shows a lower mortality than what has previously been reported for elective surgical procedures when the denominator is the total community number of operations.

Author Information

Jessica Taylor, Anaesthetic Registrar, Department of Anaesthesia, Dunedin Hospital, Dunedin; Liane Dixon, Clinical Studies Research Nurse, Department of Surgery, Christchurch Hospital, Christchurch; Rebecca Pascoe, Clinical Studies Research Nurse, Department of Surgery, Christchurch Hospital, Christchurch; Bruce Dobbs, Scientific Officer, Departments of Surgery and Gastroenterology, Christchurch Hospital, Christchurch; Ross Kennedy, Specialist Anaesthetist, Department of Anaesthesia, Christchurch Hospital, Christchurch; Frank Frizelle, HOD Department of Surgery, Christchurch Hospital, Christchurch.

Acknowledgements

The authors would like to thank Canterbury Charity Hospital, Christchurch Eye Surgery, Forte Health, St Georges Hospital and Southern Cross Hospital for their participation in this study.

Correspondence

Dr Jessica Taylor, Department of Anaesthesia, Dunedin Hospital, 201 Great King Street, Dunedin 9054.

Correspondence Email

jessica.taylor@southerndhb.govt.nz

Competing Interests

The University of Otago, Christchurch provided funding for this study, however, did not have any role in the study design, data collection, analysis and interpretation, writing of the manuscript or decision to submit for publication. No conflicts of interest were identified.

- - Story D, Leslie K, Myles P, et al. Complications and mortality in older surgical patients in Australia and New Zealand (the REASON study): a multicentre, prospective, observational study. Anaesthesia. 2010; 65:1022-30. Hamel M, Henderson W, Khuri S, et al. Surgical outcomes for patients aged 80 and older: morbidity and mortality from major noncardiac surgery. J Am Geriatr Soc. 2005; 53:424-9. Safety of Anaesthesia. A review of anaesthesia-related mortality reporting in Australia and New Zealand 2003-2005. Australian and New Zealand College of Anaesthetists 2009. Noordzij P, Poldermans D, Schouten O, et al. Postoperative mortality in The Netherlands:2028a population-based analysis of surgery-specific risk in adults. Anesthesiology. 2010; 112:1105-15. Pearse R, Moreno, R, Bauer P, et al. Mortality after surgery in Europe: a 7 day cohort study. Lancet. 2012; 380:1059-65. Leung J, Dzankic S. Relative importance of preoperative health status versus intraoperative factors in predicting postoperative adverse outcomes in geriatric surgical patients. J Am Geriatr Soc. 2001; 49:1080-1085. Bellomo R, Goldsmith D, Russell S, et al. Postoperative serious adverse events in a teaching hospital: a prospective study. Med J Austr. 2002; 176:216-8. Findlay G, Goodwin A, Protopappa K, et al. Knowing the risk: a review of the peri-operative care of surgical patients. London: National Confidential Enquiry into Patient Outcome and Death, 2011. Massarweh N, Legner V, Symons R, et al. Impact of advancing aged on abdominal surgical outcomes. Arch Surg. 2009; 144(12):1108-1114. WHO guidelines for safe surgery: 2009: safe surgery saves lives. World Health Organisation 2009.- -

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Elective surgery is increasingly common as people live longer and try to maintain their quality of life. The balance between the risks and benefits of an elective operation is an important consideration when deciding whether or not to proceed. The benefits are often relief of pain and increase in function; the risks however, are harder to qualify. There is limited data available and that which we have is often from major public hospitals, which often attract the more complex patients and a heavier workload. The real risk in a community is much harder to define, as many procedures are performed in private hospitals and other smaller public hospitals.In a prospective study of non-cardiac surgical patients aged 70 years or older across Australia and New Zealand, the 30-day mortality was 5%.1 This study is one of only a few that have prospectively analysed surgical outcomes across a wide range of specialties, and it was the largest study of its kind in Australasia. The results however, may not be generalisable to younger patients or patients having surgery at private hospitals, and self-selection of participating hospitals means that they may not be representative of all hospitals in Australasia.The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) is the largest database of postoperative mortality worldwide. It has some limitations, including that large teaching hospitals are overrepresented and studies from it are retrospective in nature. Due to the differences in healthcare delivery in the US compared with Australasia, the data is unlikely to be applicable here. However, an NSQIP study did show a comparable 30-day mortality to the Australasian study.2In New Zealand the Perioperative Mortality Review Committee (POMRC) has the role of providing advice to the Health Quality and Safety commission on how to reduce the number of perioperative deaths. POMRC uses Ministry of Health databases, which have the limitations of coding accuracy and data completeness, and do not include patients that have been treated in private hospitals. POMRC reports have limited use because they are mainly focused on specific procedures.Surgeons and anaesthetists have the important job of informing patients and their families of the risks of any procedure. This can be difficult given the limited contemporary local data available on perioperative mortality. The aim of this study was to determine the mortality after elective surgery at a total community level with inclusion of all patients undergoing elective surgery in Christchurch, New Zealand, forming the largest cohort of elective surgical patients in Australasia and allowing us to describe the mortality of different patient groups within the cohort.MethodThis study was conducted at eight hospitals in Christchurch during November 2014. Hospitals that participated were all Christchurch hospitals where surgery is undertaken (public hospitals: Christchurch Hospital, Christchurch Womens Hospital and Burwood Hospital; and private hospitals: Canterbury Charity Hospital, Christchurch Eye Surgery, Forte Health, St Georges Hospital and Southern Cross Hospital). The University of Otago Human Ethics Committee approved this study and approval was also given by each participating hospital.We studied all patients who underwent elective surgery. Elective surgery was defined as procedures scheduled on a routine elective operating list. Patients were identified for inclusion in the study from operating theatre lists at each hospital. No patients were excluded from the study. For each patient, we collected demographic data, National Health Index (NHI) number, American Society of Anaesthesiologists physical status classification (ASA), type of anaesthetic and surgical specialty. ASA was used as an indicator of preoperative comorbidity. Patients were classified by surgical specialty in a similar way to the Australasian study. For analysis, patients were classified into six age groups: <20 years, 20-34 years, 35-49 years, 50-64 years, 65-79 years and 226580 years, and as either having had a general anaesthetic, sedation or local anaesthetic only.The primary outcome was 30-day mortality defined as death within 30 days after surgery, and the secondary outcome was 90-day mortality defined as death within 90 days after surgery. Dates of deaths were determined by matching NHI numbers with death records held by the Ministry of Health. The clinical records of patients that died were reviewed in order to find the cause of death. A death certificate was obtained where the cause of death could not be determined. The cause of death was classified according to the system used by the Australian and New Zealand College of Anaesthetists (ANZCA) Mortality Working Group, which classifies deaths based on the degree to which the death was anaesthesia-related.3Study data was de-identified. Data was pooled from all hospitals and analysed using computer software (Minitab00ae Release 14.11.1, Minitab Inc, PA, USA and StatView for Windows, Version 5.0.1, SAS Institute Inc, Cary, NC, USA).ResultsFour thousand seven hundred and fifteen patients were identified and included in this study. Two thousand seven hundred and fifty-eight (55%) were female and the median age was 56 years (range 0-99 years) (Table 1). By day 30, 11 (0.2%) patients had died and by day 90, 27 (0.6%) patients had died. Males and females had similar mortality. The highest mortality was in patients aged 80 years or older (30-day mortality 0.8% and 90-day mortality 2.1%). There were no deaths in patients aged younger than 35 years. Mortality did not vary by day of the week of surgery. There was no increase in mortality in patients that underwent surgery on a Friday compared with other days of the week.Table 1:Mortality by sex, ethnicity and age group. n 30-day mortality 90-day mortality Sex Male 2,135 (45%) 7 (0.3%) 13 (0.6%) Female 2,578 (55%) 4 (0.2%) 14 (0.5%) Unknown 2 (0.04%) 0 (0.0%) 0 (0.0%) Ethnicity European 4,105 (87.1%) 8 (0.2%) 24 (0.6%) M1ori 185 (3.9%) 1 (0.5%) 1 (0.5%) Asian 124 (2.6%) 2 (1.6%) 2 (1.6%) Other/Unknown 301 (6.4%) 0 (0.0%) 0 (0.0%) Age group (years) <20 525 (11.1%) 0 (0.0%) 0 (0.0%) 20-34 568 (12.0%) 0 (0.0%) 0 (0.0%) 35-49 816 (17.3%) 1 (0.1%) 1 (0.1%) 50-64 1,268 (26.9%) 2 (0.2%) 4 (0.3%) 65-79 1,150 (24.4%) 5 (0.4%) 14 (1.2%) 226580 384 (8.1%) 3 (0.8%) 8 (2.1%) Unknown 4 (0.1%) 0 (0.0%) 0 (0.0%) Total 4715 11 (0.2%) 27 (0.6%) Values are number (proportion).The majority of patients had a general anaesthetic (3,142 patients, 67%) (Table 2). Patients who had sedation had a higher 30-day and 90-day mortality than patients who had a general anaesthetic or local anaesthetic only. In patients who had a general anaesthetic, 420 patients (13.3%) had severe systemic disease; that is, they were ASA 3 or 4. The 30-day mortality for these patients was 1.0% and the 90-day mortality was 1.9%. For patients that were ASA 1 or 2, the 30-day and 90-day mortality was 0.04% (one death out of 2,722 patients).Table 2: Mortality by type of anaesthetic and ASA (for patients who had a general anaesthetic). Type of anaesthetic n 30-day mortality 90-day mortality General anaesthetic 3,142 (67%) 5 (0.2%) 9 (0.3%) ASA 1 1,457 (30.9%) 0 (0.0%) 0 (0.0%) ASA 2 1,265 (26.8%) 1 (0.1%) 1 (0.1%) ASA 3 401 (8.5%) 2 (0.5%) 5 (1.2%) ASA 4 19 (0.4%) 2 (10.5%) 3 (15.8%) Sedation 628 (13.3%) 4 (0.6%) 12 (1.9%) Local anaesthetic only 727 (15.4%) 1 (0.1%) 5 (0.7%) Unknown 218 (4.6%) 1 (0.5%) 1 (0.5%) Values are number (proportion). ASA 1, a healthy patient with no systemic disease; ASA 2, mild to moderate systemic disease; ASA 3, severe systemic disease imposing functional limitation on patient; ASA 4, severe systemic disease, which is a constant threat to life.When patients who had a general anaesthetic were categorised by age group and ASA, the highest 90-day mortality was patients aged 80 years or older that were ASA 4 (one death out of four patients, 25%) (Table 3). In patients aged 65 to 79 years and ASA 3 or 4, the 30-day mortality was 2.1% and the 90-day mortality was 3.5%, and in patients aged 80 years or older and ASA 3 or 4, the 30-day mortality was 1.2% and the 90-day mortality was 3.7%. There were no deaths of patients aged 65 years or older that were ASA 1 or 2.Table 3: Mortality by age group, type of anaesthetic and ASA (for patients who had a general anaesthetic).Values are number (proportion). ASA 1, a healthy patient with no systemic disease; ASA 2, mild to moderate systemic disease; ASA 3, severe systemic disease imposing functional limitation on patient; ASA 4, severe systemic disease, which is a constant threat to life.The specialty that had the greatest representation in our cohort was endoscopy (948 patients, 20.1%) followed by orthopaedics (814 patients, 17.3%) (Table 4). Specialties that had one or more death were cardiology, cardiothoracic, general, neurosurgery, ophthalmology, plastics, urology, endoscopy and bronchoscopy. Neurosurgery had the highest 30-day mortality of 4.3% (two deaths out of 47 patients) followed by cardiothoracic surgery with a 30-day mortality of 2.4% (two deaths out of 41 patients).Table 4: Mortality by surgical specialty. Surgical specialty n 30-day mortality 90-day mortality Cardiology 64 (1.4%) 1 (1.6%) 1 (1.6%) Cardiothoracic 41 (0.9%) 1 (2.4%) 1 (2.4%) Dental 75 (1.6%) 0 (0.0%) 0 (0.0%) Endocrinology 1 (0.0%) 0 (0.0%) 0 (0.0%) Otolaryngology 358 (7.6%) 0 (0.0%) 0 (0.0%) General 451 (9.6%) 0 (0.0%) 1 (0.2%) Gynaecology 429 (9.1%) 0 (0.0%) 0 (0.0%) Maxilllofacial 28 (0.6%) 0 (0.0%) 0 (0.0%) Neurosurgery 47 (1.0%) 2 (4.3%) 2 (4.3%) Obstetrics 43 (0.9%) 0 (0.0%) 0 (0.0%) Opthalmology 461 (9.8%) 3 (0.7%) 4 (0.9%) Orthopaedics 814 (17.3%) 0 (0.0%) 0 (0.0%) Paediatrics 44 (0.9%) 0 (0.0%) 0 (0.0%) Plastics 477 (10.1%) 0 (0.0%) 4 (0.8%) Urology 164 (3.5%) 0 (0.0%) 1 (0.6%) Vascular 58 (1.2%) 0 (0.0%) 0 (0.0%) Spinal 22 (0.5%) 0 (0.0%) 0 (0.0%) Endoscopy 948 (20.1%) 4 (0.4%) 10 (1.1%) Bronchoscopy 37 (0.8%) 0 (0.0%) 3 (8.1%) Other 153 (3.2%) 0 (0.0%) 0 (0.0%) Values are number (proportion).Of the 27 deaths within 90 days after surgery, one was possibly anaesthesia-related (0.02%). Twenty-two deaths (0.5%) were not anaesthesia-related and the cause of death was unable to be assessed for four patients (0.1%). The one death that was possibly anaesthesia-related occurred in a patient aged 65-79 years who had undergone a neurosurgical procedure under local anaesthetic only.DiscussionIn this prospective observational study of patients undergoing elective surgery in Christchurch we found a 30-day mortality of 0.2% and 90-day mortality of 0.6%. In patients aged 65 years or older the 30-day mortality was 0.5%, and in patients aged 80 years or older the 30-day mortality was 0.8%. These results are not consistent with those of the Australasian study that found a 30-day mortality of 5% in patients aged 70 years or older; however, they are consistent with our expectation that the mortality of patients in our cohort would be lower than that found in the Australasian study.The Australasian study had some limitations that we think may have contributed to a high mortality. Large teaching hospitals were over represented, and no private hospitals were included. Some specialties such as neurosurgery and thoracic surgery may have been over represented because these types of surgery are usually only performed at large teaching hospitals. An NSQIP study reported that thoracic surgery had the highest mortality,2 so patients undergoing thoracic surgery may have disproportionately contributed to the mortality. Patients operated on in public hospitals may have higher preoperative comorbidity, which would mean that the Australasian cohort might have included a disproportionately high number of patients with a high ASA. Our study avoided these limitations by including all patients undergoing any type of surgery at all hospitals. We think that our findings are more likely to reflect the actual situation in New Zealand.Most of the postoperative mortality data that is currently available is from retrospective reviews of administrative databases, and often these are focused on one specific procedure or specialty. One of the largest retrospective observational studies of postoperative mortality showed a postoperative mortality of 1.85% in patients undergoing elective open surgical procedures.4 Our mortality is significantly lower than this. One of the reasons for this may be that we included patients having laparoscopic and diagnostic procedures, which have a lower mortality that open procedures. There are few studies that have prospectively examined mortality across a range of surgical specialties. Most of these studies have used in-hospital mortality as the primary outcome. The first large prospective international study of surgical outcomes showed an in-hospital mortality of 4%.5 Some other older prospective studies of in-hospital mortality have shown similar high mortality rates.6,7 These studies included elective as well as urgent and emergency procedures, which may explain the high mortality. One of the most recent studies to prospectively examine 30-day mortality is a large study performed in the UK, which showed a 30-day mortality for elective surgery of 0.4%.8 Our results are consistent with these findings and the methods of this study were similar to ours. The largest US study to prospectively examine mortality data showed a 30-day mortality of 8% in patients aged 80 years or older and 3% in patients aged less than 80 years.2 These figures are significantly higher than ours, however, the cohort in this study is unlikely to be representative of the whole population because only patients that underwent surgery at Veterans Affairs Medical Centres were included.Advances in perioperative care and minimally invasive surgery have enabled older and sicker patients to have surgery. It is well known that increasing age and ASA are associated with increasing mortality. One study previously mentioned showed that age and comorbidity were independent predictors of 30-day mortality and in patients aged 80 or older ASA was the strongest predictor of mortality.2 Another study showed that patients that are ASA 4 are at 6.75 times the risk of death compared with patients that are ASA 1.5 In our study, 30-day and 90-day mortality increased with each increasing age group and ASA, which is consistent with the findings of other studies.2,5,6,9Sedation is often used as an alternative to general anaesthetic in patients who are considered to be at a too high risk to have a general anaesthetic, so these patients are likely to have high preoperative comorbidity. This may explain the higher mortality of these patients compared with the entire cohort. The high mortality in neurosurgery is likely to be multifactorial but is likely due to the complex nature of neurosurgery as well as the particularly high risk of death of some procedures. For example, in one study previously mentioned, craniotomy for brain tumor had one of the highest mortalities of all procedures at 16.3%.2 The high mortality we saw in cardiothoracic surgery compared with other specialties is consistent with other studies.1,2,4The most recent review of anaesthesia-related mortality by the ANZCA Mortality Working Group showed that over a three-year period, the total number of deaths reported was 1,404, and of these, 112 (8.0%) were considered to be wholly or partly related to anaesthetic factors.3 Deaths included in this review are those that are reported to ANZCA mortality review committees, and these are usually only those that occur within 24-48 hours of an anaesthetic. We used the same system and found that 3.7% of our deaths were anaesthesia-related. Caution should be taken in comparing this figure to that found in the review due to the small numbers of deaths and the differences in the nature of the data. The importance of calculating this figure in our study is to highlight that some postoperative deaths are directly or indirectly related to anaesthesia, and in order to reduce perioperative mortality there must be a system by which all perioperative deaths are reviewed.Number of deaths on the day of surgery and number of in-hospital deaths after surgery are identified in the WHO guidelines for safe surgery 2009 as vital statistics that should be collected on a national level as indicators of performance of a health system. Clearly the WHO considers perioperative mortality data in providing insight into risks associated with surgery. We included both 30-day and 90-day mortality, given we would be able to review all deaths and identify the causes. As expected, the majority were due to progression of the underlying disease and only one was possibly anaesthesia-related.This study has several limitations. Firstly, this data was collected over a one-month period, and this group of patients may not be representative of patients undergoing surgery year round. The data we collected did not allow us to calculate the association between particular comorbidities and mortality, nor particular complications and mortality. The major strength of our study is that it has a large contemporary patient sample with prospective data on all patients, including a wide range of procedures being performed at both public and private hospitals. This is the largest study of this type to have been conducted in Australia and New Zealand.This study provides a unique snapshot of perioperative mortality for patients undergoing elective surgery in Christchurch. We think the results are reassuring in that the mortality rates are similar if not lower than what has been shown in other similar studies. Even though we found what we consider a low mortality rate, this study serves as a reminder of the importance of considering the risks including death of a particular patient undergoing a particular procedure when counseling a patient about elective surgery.

Summary

Abstract

Aim

Most studies assessing mortality after surgery have been undertaken in major public hospitals or are procedure specific. The aim of this study was to determine mortality after elective surgery at a total community level with inclusion of all patients undergoing elective surgery.

Method

This was a prospective study of all patients that underwent elective surgery in Christchurch, New Zealand, within a calendar month. For each patient, we collected demographic data, American Society of Anaesthesiologists physical status classification (ASA), type of anaesthetic and surgical specialty. The primary outcome was 30-day mortality and the secondary outcome was 90-day mortality.

Results

Four thousand seven hundred and fifteen patients were included in this study. Two thousand five hundred and seventy-eight (55%) were female and the median age was 56 years (range 0-99 years). Three thousand one hundred and forty-two (67%) patients had a general anaesthetic. By day 30, 11 (0.2%) patients had died and by day 90, 27 (0.6%) patients had died. Of the 27 deaths within 90 days after surgery, one was possibly anaesthesia-related (0.02%), while the majority were due to progression of disease (18).

Conclusion

This study shows a lower mortality than what has previously been reported for elective surgical procedures when the denominator is the total community number of operations.

Author Information

Jessica Taylor, Anaesthetic Registrar, Department of Anaesthesia, Dunedin Hospital, Dunedin; Liane Dixon, Clinical Studies Research Nurse, Department of Surgery, Christchurch Hospital, Christchurch; Rebecca Pascoe, Clinical Studies Research Nurse, Department of Surgery, Christchurch Hospital, Christchurch; Bruce Dobbs, Scientific Officer, Departments of Surgery and Gastroenterology, Christchurch Hospital, Christchurch; Ross Kennedy, Specialist Anaesthetist, Department of Anaesthesia, Christchurch Hospital, Christchurch; Frank Frizelle, HOD Department of Surgery, Christchurch Hospital, Christchurch.

Acknowledgements

The authors would like to thank Canterbury Charity Hospital, Christchurch Eye Surgery, Forte Health, St Georges Hospital and Southern Cross Hospital for their participation in this study.

Correspondence

Dr Jessica Taylor, Department of Anaesthesia, Dunedin Hospital, 201 Great King Street, Dunedin 9054.

Correspondence Email

jessica.taylor@southerndhb.govt.nz

Competing Interests

The University of Otago, Christchurch provided funding for this study, however, did not have any role in the study design, data collection, analysis and interpretation, writing of the manuscript or decision to submit for publication. No conflicts of interest were identified.

- - Story D, Leslie K, Myles P, et al. Complications and mortality in older surgical patients in Australia and New Zealand (the REASON study): a multicentre, prospective, observational study. Anaesthesia. 2010; 65:1022-30. Hamel M, Henderson W, Khuri S, et al. Surgical outcomes for patients aged 80 and older: morbidity and mortality from major noncardiac surgery. J Am Geriatr Soc. 2005; 53:424-9. Safety of Anaesthesia. A review of anaesthesia-related mortality reporting in Australia and New Zealand 2003-2005. Australian and New Zealand College of Anaesthetists 2009. Noordzij P, Poldermans D, Schouten O, et al. Postoperative mortality in The Netherlands:2028a population-based analysis of surgery-specific risk in adults. Anesthesiology. 2010; 112:1105-15. Pearse R, Moreno, R, Bauer P, et al. Mortality after surgery in Europe: a 7 day cohort study. Lancet. 2012; 380:1059-65. Leung J, Dzankic S. Relative importance of preoperative health status versus intraoperative factors in predicting postoperative adverse outcomes in geriatric surgical patients. J Am Geriatr Soc. 2001; 49:1080-1085. Bellomo R, Goldsmith D, Russell S, et al. Postoperative serious adverse events in a teaching hospital: a prospective study. Med J Austr. 2002; 176:216-8. Findlay G, Goodwin A, Protopappa K, et al. Knowing the risk: a review of the peri-operative care of surgical patients. London: National Confidential Enquiry into Patient Outcome and Death, 2011. Massarweh N, Legner V, Symons R, et al. Impact of advancing aged on abdominal surgical outcomes. Arch Surg. 2009; 144(12):1108-1114. WHO guidelines for safe surgery: 2009: safe surgery saves lives. World Health Organisation 2009.- -

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Elective surgery is increasingly common as people live longer and try to maintain their quality of life. The balance between the risks and benefits of an elective operation is an important consideration when deciding whether or not to proceed. The benefits are often relief of pain and increase in function; the risks however, are harder to qualify. There is limited data available and that which we have is often from major public hospitals, which often attract the more complex patients and a heavier workload. The real risk in a community is much harder to define, as many procedures are performed in private hospitals and other smaller public hospitals.In a prospective study of non-cardiac surgical patients aged 70 years or older across Australia and New Zealand, the 30-day mortality was 5%.1 This study is one of only a few that have prospectively analysed surgical outcomes across a wide range of specialties, and it was the largest study of its kind in Australasia. The results however, may not be generalisable to younger patients or patients having surgery at private hospitals, and self-selection of participating hospitals means that they may not be representative of all hospitals in Australasia.The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) is the largest database of postoperative mortality worldwide. It has some limitations, including that large teaching hospitals are overrepresented and studies from it are retrospective in nature. Due to the differences in healthcare delivery in the US compared with Australasia, the data is unlikely to be applicable here. However, an NSQIP study did show a comparable 30-day mortality to the Australasian study.2In New Zealand the Perioperative Mortality Review Committee (POMRC) has the role of providing advice to the Health Quality and Safety commission on how to reduce the number of perioperative deaths. POMRC uses Ministry of Health databases, which have the limitations of coding accuracy and data completeness, and do not include patients that have been treated in private hospitals. POMRC reports have limited use because they are mainly focused on specific procedures.Surgeons and anaesthetists have the important job of informing patients and their families of the risks of any procedure. This can be difficult given the limited contemporary local data available on perioperative mortality. The aim of this study was to determine the mortality after elective surgery at a total community level with inclusion of all patients undergoing elective surgery in Christchurch, New Zealand, forming the largest cohort of elective surgical patients in Australasia and allowing us to describe the mortality of different patient groups within the cohort.MethodThis study was conducted at eight hospitals in Christchurch during November 2014. Hospitals that participated were all Christchurch hospitals where surgery is undertaken (public hospitals: Christchurch Hospital, Christchurch Womens Hospital and Burwood Hospital; and private hospitals: Canterbury Charity Hospital, Christchurch Eye Surgery, Forte Health, St Georges Hospital and Southern Cross Hospital). The University of Otago Human Ethics Committee approved this study and approval was also given by each participating hospital.We studied all patients who underwent elective surgery. Elective surgery was defined as procedures scheduled on a routine elective operating list. Patients were identified for inclusion in the study from operating theatre lists at each hospital. No patients were excluded from the study. For each patient, we collected demographic data, National Health Index (NHI) number, American Society of Anaesthesiologists physical status classification (ASA), type of anaesthetic and surgical specialty. ASA was used as an indicator of preoperative comorbidity. Patients were classified by surgical specialty in a similar way to the Australasian study. For analysis, patients were classified into six age groups: <20 years, 20-34 years, 35-49 years, 50-64 years, 65-79 years and 226580 years, and as either having had a general anaesthetic, sedation or local anaesthetic only.The primary outcome was 30-day mortality defined as death within 30 days after surgery, and the secondary outcome was 90-day mortality defined as death within 90 days after surgery. Dates of deaths were determined by matching NHI numbers with death records held by the Ministry of Health. The clinical records of patients that died were reviewed in order to find the cause of death. A death certificate was obtained where the cause of death could not be determined. The cause of death was classified according to the system used by the Australian and New Zealand College of Anaesthetists (ANZCA) Mortality Working Group, which classifies deaths based on the degree to which the death was anaesthesia-related.3Study data was de-identified. Data was pooled from all hospitals and analysed using computer software (Minitab00ae Release 14.11.1, Minitab Inc, PA, USA and StatView for Windows, Version 5.0.1, SAS Institute Inc, Cary, NC, USA).ResultsFour thousand seven hundred and fifteen patients were identified and included in this study. Two thousand seven hundred and fifty-eight (55%) were female and the median age was 56 years (range 0-99 years) (Table 1). By day 30, 11 (0.2%) patients had died and by day 90, 27 (0.6%) patients had died. Males and females had similar mortality. The highest mortality was in patients aged 80 years or older (30-day mortality 0.8% and 90-day mortality 2.1%). There were no deaths in patients aged younger than 35 years. Mortality did not vary by day of the week of surgery. There was no increase in mortality in patients that underwent surgery on a Friday compared with other days of the week.Table 1:Mortality by sex, ethnicity and age group. n 30-day mortality 90-day mortality Sex Male 2,135 (45%) 7 (0.3%) 13 (0.6%) Female 2,578 (55%) 4 (0.2%) 14 (0.5%) Unknown 2 (0.04%) 0 (0.0%) 0 (0.0%) Ethnicity European 4,105 (87.1%) 8 (0.2%) 24 (0.6%) M1ori 185 (3.9%) 1 (0.5%) 1 (0.5%) Asian 124 (2.6%) 2 (1.6%) 2 (1.6%) Other/Unknown 301 (6.4%) 0 (0.0%) 0 (0.0%) Age group (years) <20 525 (11.1%) 0 (0.0%) 0 (0.0%) 20-34 568 (12.0%) 0 (0.0%) 0 (0.0%) 35-49 816 (17.3%) 1 (0.1%) 1 (0.1%) 50-64 1,268 (26.9%) 2 (0.2%) 4 (0.3%) 65-79 1,150 (24.4%) 5 (0.4%) 14 (1.2%) 226580 384 (8.1%) 3 (0.8%) 8 (2.1%) Unknown 4 (0.1%) 0 (0.0%) 0 (0.0%) Total 4715 11 (0.2%) 27 (0.6%) Values are number (proportion).The majority of patients had a general anaesthetic (3,142 patients, 67%) (Table 2). Patients who had sedation had a higher 30-day and 90-day mortality than patients who had a general anaesthetic or local anaesthetic only. In patients who had a general anaesthetic, 420 patients (13.3%) had severe systemic disease; that is, they were ASA 3 or 4. The 30-day mortality for these patients was 1.0% and the 90-day mortality was 1.9%. For patients that were ASA 1 or 2, the 30-day and 90-day mortality was 0.04% (one death out of 2,722 patients).Table 2: Mortality by type of anaesthetic and ASA (for patients who had a general anaesthetic). Type of anaesthetic n 30-day mortality 90-day mortality General anaesthetic 3,142 (67%) 5 (0.2%) 9 (0.3%) ASA 1 1,457 (30.9%) 0 (0.0%) 0 (0.0%) ASA 2 1,265 (26.8%) 1 (0.1%) 1 (0.1%) ASA 3 401 (8.5%) 2 (0.5%) 5 (1.2%) ASA 4 19 (0.4%) 2 (10.5%) 3 (15.8%) Sedation 628 (13.3%) 4 (0.6%) 12 (1.9%) Local anaesthetic only 727 (15.4%) 1 (0.1%) 5 (0.7%) Unknown 218 (4.6%) 1 (0.5%) 1 (0.5%) Values are number (proportion). ASA 1, a healthy patient with no systemic disease; ASA 2, mild to moderate systemic disease; ASA 3, severe systemic disease imposing functional limitation on patient; ASA 4, severe systemic disease, which is a constant threat to life.When patients who had a general anaesthetic were categorised by age group and ASA, the highest 90-day mortality was patients aged 80 years or older that were ASA 4 (one death out of four patients, 25%) (Table 3). In patients aged 65 to 79 years and ASA 3 or 4, the 30-day mortality was 2.1% and the 90-day mortality was 3.5%, and in patients aged 80 years or older and ASA 3 or 4, the 30-day mortality was 1.2% and the 90-day mortality was 3.7%. There were no deaths of patients aged 65 years or older that were ASA 1 or 2.Table 3: Mortality by age group, type of anaesthetic and ASA (for patients who had a general anaesthetic).Values are number (proportion). ASA 1, a healthy patient with no systemic disease; ASA 2, mild to moderate systemic disease; ASA 3, severe systemic disease imposing functional limitation on patient; ASA 4, severe systemic disease, which is a constant threat to life.The specialty that had the greatest representation in our cohort was endoscopy (948 patients, 20.1%) followed by orthopaedics (814 patients, 17.3%) (Table 4). Specialties that had one or more death were cardiology, cardiothoracic, general, neurosurgery, ophthalmology, plastics, urology, endoscopy and bronchoscopy. Neurosurgery had the highest 30-day mortality of 4.3% (two deaths out of 47 patients) followed by cardiothoracic surgery with a 30-day mortality of 2.4% (two deaths out of 41 patients).Table 4: Mortality by surgical specialty. Surgical specialty n 30-day mortality 90-day mortality Cardiology 64 (1.4%) 1 (1.6%) 1 (1.6%) Cardiothoracic 41 (0.9%) 1 (2.4%) 1 (2.4%) Dental 75 (1.6%) 0 (0.0%) 0 (0.0%) Endocrinology 1 (0.0%) 0 (0.0%) 0 (0.0%) Otolaryngology 358 (7.6%) 0 (0.0%) 0 (0.0%) General 451 (9.6%) 0 (0.0%) 1 (0.2%) Gynaecology 429 (9.1%) 0 (0.0%) 0 (0.0%) Maxilllofacial 28 (0.6%) 0 (0.0%) 0 (0.0%) Neurosurgery 47 (1.0%) 2 (4.3%) 2 (4.3%) Obstetrics 43 (0.9%) 0 (0.0%) 0 (0.0%) Opthalmology 461 (9.8%) 3 (0.7%) 4 (0.9%) Orthopaedics 814 (17.3%) 0 (0.0%) 0 (0.0%) Paediatrics 44 (0.9%) 0 (0.0%) 0 (0.0%) Plastics 477 (10.1%) 0 (0.0%) 4 (0.8%) Urology 164 (3.5%) 0 (0.0%) 1 (0.6%) Vascular 58 (1.2%) 0 (0.0%) 0 (0.0%) Spinal 22 (0.5%) 0 (0.0%) 0 (0.0%) Endoscopy 948 (20.1%) 4 (0.4%) 10 (1.1%) Bronchoscopy 37 (0.8%) 0 (0.0%) 3 (8.1%) Other 153 (3.2%) 0 (0.0%) 0 (0.0%) Values are number (proportion).Of the 27 deaths within 90 days after surgery, one was possibly anaesthesia-related (0.02%). Twenty-two deaths (0.5%) were not anaesthesia-related and the cause of death was unable to be assessed for four patients (0.1%). The one death that was possibly anaesthesia-related occurred in a patient aged 65-79 years who had undergone a neurosurgical procedure under local anaesthetic only.DiscussionIn this prospective observational study of patients undergoing elective surgery in Christchurch we found a 30-day mortality of 0.2% and 90-day mortality of 0.6%. In patients aged 65 years or older the 30-day mortality was 0.5%, and in patients aged 80 years or older the 30-day mortality was 0.8%. These results are not consistent with those of the Australasian study that found a 30-day mortality of 5% in patients aged 70 years or older; however, they are consistent with our expectation that the mortality of patients in our cohort would be lower than that found in the Australasian study.The Australasian study had some limitations that we think may have contributed to a high mortality. Large teaching hospitals were over represented, and no private hospitals were included. Some specialties such as neurosurgery and thoracic surgery may have been over represented because these types of surgery are usually only performed at large teaching hospitals. An NSQIP study reported that thoracic surgery had the highest mortality,2 so patients undergoing thoracic surgery may have disproportionately contributed to the mortality. Patients operated on in public hospitals may have higher preoperative comorbidity, which would mean that the Australasian cohort might have included a disproportionately high number of patients with a high ASA. Our study avoided these limitations by including all patients undergoing any type of surgery at all hospitals. We think that our findings are more likely to reflect the actual situation in New Zealand.Most of the postoperative mortality data that is currently available is from retrospective reviews of administrative databases, and often these are focused on one specific procedure or specialty. One of the largest retrospective observational studies of postoperative mortality showed a postoperative mortality of 1.85% in patients undergoing elective open surgical procedures.4 Our mortality is significantly lower than this. One of the reasons for this may be that we included patients having laparoscopic and diagnostic procedures, which have a lower mortality that open procedures. There are few studies that have prospectively examined mortality across a range of surgical specialties. Most of these studies have used in-hospital mortality as the primary outcome. The first large prospective international study of surgical outcomes showed an in-hospital mortality of 4%.5 Some other older prospective studies of in-hospital mortality have shown similar high mortality rates.6,7 These studies included elective as well as urgent and emergency procedures, which may explain the high mortality. One of the most recent studies to prospectively examine 30-day mortality is a large study performed in the UK, which showed a 30-day mortality for elective surgery of 0.4%.8 Our results are consistent with these findings and the methods of this study were similar to ours. The largest US study to prospectively examine mortality data showed a 30-day mortality of 8% in patients aged 80 years or older and 3% in patients aged less than 80 years.2 These figures are significantly higher than ours, however, the cohort in this study is unlikely to be representative of the whole population because only patients that underwent surgery at Veterans Affairs Medical Centres were included.Advances in perioperative care and minimally invasive surgery have enabled older and sicker patients to have surgery. It is well known that increasing age and ASA are associated with increasing mortality. One study previously mentioned showed that age and comorbidity were independent predictors of 30-day mortality and in patients aged 80 or older ASA was the strongest predictor of mortality.2 Another study showed that patients that are ASA 4 are at 6.75 times the risk of death compared with patients that are ASA 1.5 In our study, 30-day and 90-day mortality increased with each increasing age group and ASA, which is consistent with the findings of other studies.2,5,6,9Sedation is often used as an alternative to general anaesthetic in patients who are considered to be at a too high risk to have a general anaesthetic, so these patients are likely to have high preoperative comorbidity. This may explain the higher mortality of these patients compared with the entire cohort. The high mortality in neurosurgery is likely to be multifactorial but is likely due to the complex nature of neurosurgery as well as the particularly high risk of death of some procedures. For example, in one study previously mentioned, craniotomy for brain tumor had one of the highest mortalities of all procedures at 16.3%.2 The high mortality we saw in cardiothoracic surgery compared with other specialties is consistent with other studies.1,2,4The most recent review of anaesthesia-related mortality by the ANZCA Mortality Working Group showed that over a three-year period, the total number of deaths reported was 1,404, and of these, 112 (8.0%) were considered to be wholly or partly related to anaesthetic factors.3 Deaths included in this review are those that are reported to ANZCA mortality review committees, and these are usually only those that occur within 24-48 hours of an anaesthetic. We used the same system and found that 3.7% of our deaths were anaesthesia-related. Caution should be taken in comparing this figure to that found in the review due to the small numbers of deaths and the differences in the nature of the data. The importance of calculating this figure in our study is to highlight that some postoperative deaths are directly or indirectly related to anaesthesia, and in order to reduce perioperative mortality there must be a system by which all perioperative deaths are reviewed.Number of deaths on the day of surgery and number of in-hospital deaths after surgery are identified in the WHO guidelines for safe surgery 2009 as vital statistics that should be collected on a national level as indicators of performance of a health system. Clearly the WHO considers perioperative mortality data in providing insight into risks associated with surgery. We included both 30-day and 90-day mortality, given we would be able to review all deaths and identify the causes. As expected, the majority were due to progression of the underlying disease and only one was possibly anaesthesia-related.This study has several limitations. Firstly, this data was collected over a one-month period, and this group of patients may not be representative of patients undergoing surgery year round. The data we collected did not allow us to calculate the association between particular comorbidities and mortality, nor particular complications and mortality. The major strength of our study is that it has a large contemporary patient sample with prospective data on all patients, including a wide range of procedures being performed at both public and private hospitals. This is the largest study of this type to have been conducted in Australia and New Zealand.This study provides a unique snapshot of perioperative mortality for patients undergoing elective surgery in Christchurch. We think the results are reassuring in that the mortality rates are similar if not lower than what has been shown in other similar studies. Even though we found what we consider a low mortality rate, this study serves as a reminder of the importance of considering the risks including death of a particular patient undergoing a particular procedure when counseling a patient about elective surgery.

Summary

Abstract

Aim

Most studies assessing mortality after surgery have been undertaken in major public hospitals or are procedure specific. The aim of this study was to determine mortality after elective surgery at a total community level with inclusion of all patients undergoing elective surgery.

Method

This was a prospective study of all patients that underwent elective surgery in Christchurch, New Zealand, within a calendar month. For each patient, we collected demographic data, American Society of Anaesthesiologists physical status classification (ASA), type of anaesthetic and surgical specialty. The primary outcome was 30-day mortality and the secondary outcome was 90-day mortality.

Results

Four thousand seven hundred and fifteen patients were included in this study. Two thousand five hundred and seventy-eight (55%) were female and the median age was 56 years (range 0-99 years). Three thousand one hundred and forty-two (67%) patients had a general anaesthetic. By day 30, 11 (0.2%) patients had died and by day 90, 27 (0.6%) patients had died. Of the 27 deaths within 90 days after surgery, one was possibly anaesthesia-related (0.02%), while the majority were due to progression of disease (18).

Conclusion

This study shows a lower mortality than what has previously been reported for elective surgical procedures when the denominator is the total community number of operations.

Author Information

Jessica Taylor, Anaesthetic Registrar, Department of Anaesthesia, Dunedin Hospital, Dunedin; Liane Dixon, Clinical Studies Research Nurse, Department of Surgery, Christchurch Hospital, Christchurch; Rebecca Pascoe, Clinical Studies Research Nurse, Department of Surgery, Christchurch Hospital, Christchurch; Bruce Dobbs, Scientific Officer, Departments of Surgery and Gastroenterology, Christchurch Hospital, Christchurch; Ross Kennedy, Specialist Anaesthetist, Department of Anaesthesia, Christchurch Hospital, Christchurch; Frank Frizelle, HOD Department of Surgery, Christchurch Hospital, Christchurch.

Acknowledgements

The authors would like to thank Canterbury Charity Hospital, Christchurch Eye Surgery, Forte Health, St Georges Hospital and Southern Cross Hospital for their participation in this study.

Correspondence

Dr Jessica Taylor, Department of Anaesthesia, Dunedin Hospital, 201 Great King Street, Dunedin 9054.

Correspondence Email

jessica.taylor@southerndhb.govt.nz

Competing Interests

The University of Otago, Christchurch provided funding for this study, however, did not have any role in the study design, data collection, analysis and interpretation, writing of the manuscript or decision to submit for publication. No conflicts of interest were identified.

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