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| Journal of the New Zealand Medical Association,
14-October-2011, Vol 124 No 1344
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Outcomes from out-of-hospital
cardiac arrest in the Wellington region of New Zealand. Does use of the Fire
Service make a difference?
Andrew H Swain, Tasmin Barry, Sarah R Hoyle, Grant Haywood,
Hayley Cameron, Peter D Larsen
Survival from out of hospital cardiac arrest remains low
internationally, despite attempts to optimise clinical guidelines. Factors that
correlate with improved outcome include bystander CPR and time to
defibrillation.1,2–4
A study undertaken in Melbourne, Australia showed that
response time could be significantly decreased if a combined fire and ambulance
response system was used5 and this has been
mirrored in similar studies conducted in Stockholm and
Canada.6,7 Programmes which dispatch
firefighters (or even the police8) as a first
response team have long been in place in the USA and
Canada9 and these systems have improved
survival rates from out-of-hospital cardiac
arrest.6,7
Wellington Free Ambulance (WFA) serves an area of
approximately 4000 square kilometres and a population of 473,700 (Greater
Wellington Regional Council, June 2008). It attends three to four cardiac
arrests each week.10 Emergency 111 calls are
received by the Ambulance Communication Centre and in cases of respiratory or
cardiac arrest, these calls can be transferred manually to the New Zealand Fire
Service (NZFS) dispatch centre.
NZFS personnel are trained in CPR and the use of AEDs
(automatic external defibrillators). This training is undertaken by instructors
within the fire service and is accredited by the New Zealand Qualifications
Authority. All fire vehicles in the Wellington region carry an AED and basic
first aid supplies including oxygen, bag and mask ventilators, oropharyngeal
airways and bandages.
The study hypothesis was that the NZFS response to cardiac
arrest would be faster than that of WFA, and that this would result in improved
survival to hospital discharge. Secondary endpoints were a return of spontaneous
circulation (ROSC) and survival to hospital admission.
MethodsEmergency medical services (EMS)
system—When a 111 call consistent with cardiac arrest is received
by the ambulance communication centre, the dispatcher activates the nearest
available ambulance and can then choose to dispatch either a second ambulance or
a fire appliance. This decision was based upon the location and availability of
the second ambulance at the time. To activate a fire appliance, the ambulance
dispatcher called the fire dispatch centre directly to request assistance. Since
7th July 2009, the two dispatch centres have been linked by an Intercad system.
Ambulances are normally staffed by two paramedics and fire appliances by four
firefighters.
Study period—All out-of-hospital
cardiac arrests attended by EMS over the period 1 July 2007 to 31 December 2009
were included in the study.
All adult patients (aged over 16 years) suffering out
of hospital cardiac arrest where any type of resuscitation was started were
included in the study. Exclusion criteria included cardiac arrests resulting
from trauma, suicide or hanging, and those occurring in the presence of
paramedics.
For each case, data was collected from the New Zealand
Resuscitation Council Registry in accordance with the Utstein
template.11 For each case within the registry,
fire service dispatch records were accessed to determine whether that service
had been used and if so, its response time.
Data collected—Standard Utstein
definitions11 were used. A witnessed cardiac
arrest was one that was seen or heard by another person. If this person was a
member of EMS, then the event was classified as EMS-witnessed. Bystander CPR was
recorded if the paramedic believed that CPR was performed prior to arrival by a
member of the public, either because this was occurring on arrival or it was
said that CPR had been performed. The presenting rhythm was the first monitored
cardiac rhythm when a defibrillator was attached to the patient.
Survival to hospital admission was defined as survival
to admission beyond the emergency department.
Survival to discharge was survival to discharge alive
from the hospital acute care unit, regardless of neurological status or
destination.
The ambulance response time was defined as the
difference between the time the ambulance dispatcher received the 111 call and
the time the crew reported arrival at the scene. Both of these times were
rounded to the nearest minute. For statistical analysis, response times were
categorised as 0–4 minutes, 5–8 minutes, 9–12 minutes,
13–16 minutes and greater than 16 minutes.
The fire response time was defined as the difference
between the fire dispatcher receiving the request for assistance and the fire
crew reporting arrival at the scene. This data was taken from the fire dispatch
system log.
Statistical analysis—A
Chi-squared test was used to compare outcomes and presenting rhythms for
witnessed and unwitnessed cardiac arrests. Multinomial logistic regression was
used to examine factors associated with survival to hospital discharge and
survival to hospital admission. P-values <0.05 were considered statistically
significant. All statistical tests were performed using PASW 18.0 (SPSS,
Chicago, Il.).
ResultsDuring the study period there were 362 attempted
resuscitations. In 23 cases the cardiac arrest occurred with a paramedic in
attendance, leaving 339 out-of-hospital cardiac arrests (OHCA) in the study.
Details of these cases are provided in Table 1 and Figure 1. Overall, in 37
cases (11%) the victim survived to hospital discharge.
Table 1. Community cardiac arrests, Wellington,
2007–2009
In 192 cases (57%) the cardiac arrest was witnessed. Of
these witnessed cases, 29 (15%) survived to hospital discharge, significantly
greater than for unwitnessed cardiac arrests (8 survivors, 5%, p=0.01,
Chi-squared test). Ventricular fibrillation (VF) or ventricular tachycardia (VT)
was more likely to be the presenting rhythm in witnessed arrest compared with
unwitnessed arrest (110/192 (57%) of witnessed arrests versus 51/147 (35%) of
unwitnessed arrests, p = 0.001, Chi-squared test). A total of 161 patients
presented with an initial rhythm of VF/VT, and in this group 34 survived
(21%).
Cardiac arrest survival data from other centres in New
Zealand and overseas are summarised in Table 2.
While paired comparison of fire and ambulance response times
to the same calls demonstrates that the fire response was faster, with a mean of
6.5 minutes (standard deviation 2.5) for fire versus 9.7 minutes (standard
deviation 5.0) for ambulance, the level of documentation regarding the function
of the fire service at the cardiac arrest and the times derived from control
centres without synchronised clocks did not allow us to accurately determine
which vehicle arrived first in all cases.
From the limited number of cases for which documentation was
available, we estimate that there was an average delay of 2 minutes from
dispatch of the ambulance to the dispatch of a fire crew to the scene, such that
the fire service arrived only a minute or two before the ambulance.
Figure 1. All treated cardiac arrests in the
Wellington region from 1 June 2007 to 31 December 2009 reported in the Utstein
style
 A comparison of the cases attended by the ambulance service
alone, and by the ambulance and fire services is given in Table 3. While this
shows no difference in ROSC, survival to admission or survival to discharge
between the two groups, the cardiac arrests attended by both fire and ambulance
services were less likely to have been witnessed, less likely to have received
bystander CPR, and were more likely to have a presenting rhythm of asystole than
those attended by the ambulance service alone.
To take into consideration the differences in bystander
witnessed events, bystander CPR rates and initial presenting rhythm between the
events attended by fire and ambulance versus ambulance alone, we conducted a
multinomial logistic regression analysis of characteristics associated with both
survival to hospital admission and to hospital discharge.
The results of this are shown in Table 4. Survival to
hospital admission was associated significantly with the presenting rhythm,
witnessing of the arrest and ambulance response time, while survival to hospital
discharge was associated with the presenting rhythm, patient age and ambulance
response time. After correcting for these variables, the use of the fire service
was not shown to be a significant determinant of outcome within this model.
Table 2. Survival to hospital discharge
following out-of-hospital cardiac arrest: national and international comparisons
Table 3. Data for Fire-and-Ambulance versus
Ambulance alone
Table 4. Multivariate analysis of
characteristics associated with survival to hospital admission and to hospital
discharge
DiscussionSurvival from out-of-hospital cardiac arrest in the
Wellington region—Survival to discharge from hospital following
community cardiac arrest in Wellington has been studied over a 2.5-year period
and is compared with similar data from other national and international centres
in Table 2. Previous survival figures for all cardiac arrest rhythms in
Auckland12 and
Christchurch13 are very similar to the 11%
reported from Wellington in this paper but a number of reputable centres
overseas have lower overall survival and a few cities report better outcomes in
this category.
It is well established that an initial rhythm of VF or VT is
associated with a more favourable outcome from cardiac arrest and this is
endorsed by the survival data for VF/VT arrest contained in Figure 1. Some
centres have ceased to report survival from non-shockable cardiac rhythms and
many also exclude unwitnessed arrests in the VF/VT
category.24 Taking that into account, the
authors consider that 21% survival to hospital discharge from out-of-hospital
VF/VT in the Wellington region is more favourable than that reported
internationally from a number of centres with well developed EMS systems.
Factors affecting survival—In common
with other studies,2,3,17 survival to hospital
admission was associated significantly with a presenting rhythm of VF/VT,
witnessing of the arrest, and ambulance response
time.2,4,25 Survival to hospital discharge was
also associated with the presenting rhythm but increasing patient age had an
adverse effect which has been reported to continue after leaving
hospital.26
The rate of bystander CPR was 55% but this was not found to
be a significant determinant of outcome, which raises a question regarding the
effectiveness of CPR undertaken by lay people. This finding has highlighted a
potential shortfall in the recognition of cardiac arrest and performance of CPR
by lay persons in the region and an initiative to address this has been
introduced by Wellington Free Ambulance.
In the Wellington region, use of a dual fire and ambulance
response, as opposed to ambulance response alone, has not been shown to improve
survival from cardiac arrest. This is disappointing as basic life support (BLS)
teams consisting of either fire, police, or BLS ambulance staff working with
advanced paramedics have achieved improved outcomes in other
centres.5–8,27,28
Several factors may have contributed to an apparent lack of
benefit in Wellington and these need to be considered:
Ambulance and fire service data (Table 3)
reveal a significant reduction in witnessed arrests and bystander CPR when fire
and ambulance staff both attended the cardiac arrest. This finding may be
explained by a paucity of information regarding bystander involvement from
firefighters who were already on scene.
Another unexpected finding was a significantly higher
proportion of asystole in patients attended by both fire and ambulance staff.
This initial rhythm would have been documented by paramedics and during the
period of the study, the fire service was most commonly activated because of an
anticipated delay in paramedic arrival. It is known that the incidence of
asystole increases with time during cardiac arrest.
The principle of the ‘Chain of
Survival’1 emphasises that the earlier
the emergency services, CPR, defibrillation, and advanced life support are
activated, the better is the outcome for the patient.
Other centres have reported similar ambulance response times
and survival20,29 so a well coordinated
dual-service response is required in Wellington to improve both. Ways of
achieving this are currently under discussion but automatic dual activation for
cardiac arrest call, synchronised timings, and more comprehensive documentation
are being introduced. The focus will remain a reduction in call-to-shock times
for both fire and ambulance services.
Although our ambulance call-to-arrival times are similar to
those in several European countries, they do not compare favourably with those
quoted by some groups in North America where call-to-first-shock times of
5–6 mins have been associated with survival-to-discharge rates of 16% (for
all cardiac rhythms).22,23
ConclusionSurvival from out-of-hospital cardiac arrest in Wellington
is similar to that of other New Zealand cities and better than that reported
from several large centres overseas. Survival to hospital discharge was higher
when the emergency service response time was short, the initial cardiac rhythm
was shockable and the patient was younger.
Patients whose arrest was witnessed were more likely to
reach hospital alive. The activation of a combined fire and ambulance response
was not shown to have any beneficial impact on survival over and above that
achieved by the ambulance service alone. As a result, system changes are being
introduced to try and improve data collection and survival from community
cardiac arrest in Wellington.
Competing interests - none.
Author information:
Andrew H Swain, Senior
Lecturer in Emergency Medicine, Department of Surgery and Anaesthesia,
University of Otago, Wellington; Tasmin Barry,
5th-year Medical Student, University of Otago,
Wellington; Sarah R Hoyle, Executive Manager Clinical Services, Wellington Free
Ambulance, Wellington; Grant Haywood, Station Officer, New Zealand Fire Service,
Wellington; Hayley Cameron, Data Analyst, Wellington Free Ambulance, Wellington;
Peter D Larsen, Associate Professor in Resuscitation Medicine, University of
Otago, Wellington
Acknowledgements: Tasmin Barry was a
recipient of funds from the Wellington Medical Research Foundation (Inc) and the
University of Otago Matched Funding Summer Scholarship. We thank these
organisations for sponsoring this research.
We acknowledge the helpful advice and comments from Mr Paul
Fake, Manager of Project Heartbeat (Wellington).
Correspondence: Andrew H Swain, Senior
Lecturer in Emergency Medicine, Department of Surgery and Anaesthesia,
University of Otago, PO Box 7343, Wellington 6242, New Zealand. Fax: +64 (0)4
3895318; email: andrew.swain@otago.ac.nz
References:
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