CJEM Articles: cardiac arrest

Objective: Inducing mild hypothermia in survivors of cardiac arrest has been demonstrated to improve outcomes. Despite this, other studies have found that few resuscitation physicians have used hypothermia in clinical practice. The objective of this study was to characterize the use of induced hypothermia by Canadian emergency physicians.

Methods: An internet-based survey was distributed to all members of the Canadian Association of Emergency Physicians (CAEP). Participants were asked about their experience with, methods for and barriers to inducing hypothermia.

Results: Of the 1328 CAEP members surveyed, 247 (18.6%) responded, with the majority working in academic centres (60.3%). Ninety-five out of 202 respondents (47.0%, 95% confidence interval [CI] 40.8%-53.2%) indicated that they had induced hypothermia in clinical practice and 86 of 212 (40.6%, 95% CI 34.0%-47.2%) worked in a department that had a policy or protocol for the use of induced hypothermia. The presence of a departmental policy or protocol was strongly associated with the use of induced hypothermia (unadjusted odds ratio 10.5, 95% CI 5.3-20.8). Barriers against induced hypothermia cited by respondents included a lack of institutional policies and protocols (38.9%), and of resources (29.4%). Lack of support from consultants was relatively uncommon (8.7%) in Canadian practice.

Conclusion: Only one-half of Canadian emergency physicians report that they have used therapeutic hypothermia in practice. Emergency departments should develop policies or protocols for inducing hypothermia in cardiac arrest survivors to optimize patient outcomes.

Introduction: Do not resuscitate (DNR) orders are commonly accepted in most health care settings, but are less widely recognized in the prehospital setting. We describe the implementation of and satisfaction with a prehospital DNR protocol that allows paramedics to honour verbal and non-standard written DNR requests.

Methods: This prospective observational study reviewed all cardiac arrests in southeastern Ontario between March 1, 2003 and September 31, 2005. Following a verbal or non-standard written DNR request, paramedics completed a questionnaire and a follow-up structured telephone interview was conducted with surrogate decision makers (SDMs).

Results: There were 1890 cardiac arrests during the study period, of which 86 met our inclusion criteria. Paramedic surveys were available for 82 cases (95%), and surrogate decision makers (SDMs) were successfully contacted in 50 (58%) of them. Two SDMs declined to be interviewed. The mean patient age was 72.7 (standard deviation 13.8) years and 65% were male. Sixty-three (73%) of DNR requests were verbal, and 23 (27%) were written. The mean paramedic comfort was rated 4.9 on a 5-point Likert scale (with 5 being "very comfortable") (95% confidence interval [CI] 4.9-5.0). The mean SDM comfort was rated by paramedics as 4.9 (95% CI 4.8-4.9). SDMs reported comfort in withholding CPR in 47 of 48 cases (98%), and with paramedic care in all cases. One SDM stated that although it was consistent with the patient's wishes, she was uncomfortable having to make the DNR request.

Conclusions: Satisfaction with this novel prehospital DNR protocol was uniformly high among paramedic and SDM respondents. It appears that such a protocol is feasible and acceptable for the prehospital setting. Our conclusions are limited by a small sample size, the lack of a comparison group, and limited follow-up.

Objective: Several randomized controlled trials have suggested that mild induced hypothermia may improve neurologic outcome in comatose cardiac arrest survivors. This systematic review of randomized controlled trials was designed to determine if mild induced hypothermia improves neurologic outcome, decreases mortality, or is associated with an increased incidence of adverse events.

Data sources: The following databases were reviewed: Cochrane Controlled Trials Register (Issue 4, 2005), MEDLINE (January 1966 to November 2005), EMBASE (1980 to November 2005), CINAHL (1982 to November 2005) and Web of Science (1989 to November 2005). For each included study, references were reviewed and the primary author contacted to identify any additional studies.

Study selection: Studies that met inclusion criteria were randomized controlled trials of adult patients (>18 years of age) with primary cardiac arrest who remained comatose after return of spontaneous circulation. Patients had to be randomized to mild induced hypothermia (32°C-34°C) or normothermia within 24 hours of presentation. Only studies reporting pre-determined outcomes including discharge neurologic outcome, mortality or significant treatment-related adverse events were included. There were no language or publication restrictions.

Data synthesis: Four studies involving 436 patients, with 232 cooled to a core temperature of 32°C-34°C met inclusion criteria. Pooled data demonstrated that mild hypothermia decreased in-hospital mortality (relative ratio [RR] 0.75; 95% confidence interval [CI], 0.62-0.92) and reduced the incidence of poor neurologic outcome (RR 0.74; 95% CI, 0.62-0.84). Numbers needed to treat were 7 patients to save 1 life, and 5 patients to improve neurologic outcome. There was no evidence of treatment-limiting side effects.

Conclusions: Therapeutically induced mild hypothermia decreases in-hospital mortality and improves neurologic outcome in comatose cardiac arrest survivors. The possibility of treatment-limiting side effects cannot be excluded.

Background: Accurate prediction of survival to hospital discharge in patients who achieve return of spontaneous circulation after cardiopulmonary resuscitation (CPR) has significant ethical and socioeconomic implications. We investigated the prognostic performance of serum neuron-specific enolase (NSE), a biochemical marker of ischemic brain injury, after successful CPR.
Methods: In-hospital or out-of-hospital patients with nontraumatic normothermic cardiac arrest who achieved return of spontaneous circulation (ROSC) following at least 5 minutes of CPR were eligible. Neuron-specific enolase levels were assessed immediately, 6 hours, 12 hours and 2 days after ROSC. Subjects were followed to death or hospital discharge.
Results: Seventeen patients (7 men, 10 women) were enrolled during a 1-year period. Median (range) NSE levels in survivors and non-survivors respectively were as follows: immediately after ROSC: 14.0 μg/L (9.1-51.4 μg/L) versus 25.9 μg/L (10.2-57.5 μg/L); 6 hours after ROSC: 15.2 μg/L (9.7-30.8 μg/L) versus 25.6 μg/L (12.7-38.2 μg/L); 12 hours after ROSC: 14.0 μg/L (8.6-32.4 μg/L) versus 28.5 μg/L (11.0-50.7 μg/L); and 48 hours after ROSC: 13.1 μg/L (7.8-29.5 μg/L) versus 52.0 μg/L (29.1-254.0 μg/L). Non-survivors had significantly higher NSE levels 48 hours after ROSC than surivors (p = 0.04) and showed a trend toward higher values during the entire time course following ROSC. An NSE concentration of >30 μg/L 48 hours after ROSC predicted death with a high specificity (100%: 95% confidence interval [CI] 85%-100%), and a level of 29 μg/L or less at 48 hours predicted survival with a high specificity (100%: 95% CI 83%-100%).
Conclusions: Serum NSE levels may have clinical utility for the prediction of survival to hospital discharge in patients after ROSC following CPR over 5 minutes in duration. This study is small, and our results are limited by wide confidence intervals. Further research on ability of NSE to facilitate prediction and clinical decision-making after cardiac arrest is warranted.