Elsevier

Resuscitation

Volume 82, Issue 9, September 2011, Pages 1162-1167
Resuscitation

Clinical paper
Mild therapeutic hypothermia is associated with favourable outcome in patients after cardiac arrest with non-shockable rhythms

https://doi.org/10.1016/j.resuscitation.2011.05.022Get rights and content

Abstract

Aim

Mild therapeutic hypothermia (32–34 °C) improves neurological recovery and reduces the risk of death in comatose survivors of cardiac arrest when the initial rhythm is ventricular fibrillation or pulseless ventricular tachycardia. The aim of the presented study was to investigate the effect of mild therapeutic hypothermia (32–34 °C for 24 h) on neurological outcome and mortality in patients who had been successfully resuscitated from non-ventricular fibrillation cardiac arrest.

Methods

In this retrospective cohort study we included cardiac arrest survivors of 18 years of age or older suffering a witnessed out-of-hospital cardiac arrest with asystole or pulseless electric activity as the first documented rhythm. Data were collected from 1992 to 2009. Main outcome measures were neurological outcome within six month and mortality after six months.

Results

Three hundred and seventy-four patients were analysed. Hypothermia was induced in 135 patients. Patients who were treated with mild therapeutic hypothermia were more likely to have good neurological outcomes in comparison to patients who were not treated with hypothermia with an odds ratio of 1.84 (95% confidence interval: 1.08–3.13). In addition, the rate of mortality was significantly lower in the hypothermia group (odds ratio: 0.56; 95% confidence interval: 0.34–0.93).

Conclusion

Treatment with mild therapeutic hypothermia at a temperature of 32–34 °C for 24 h is associated with improved neurological outcome and a reduced risk of death following out-of-hospital cardiac arrest with non-shockable rhythms.

Introduction

The incidence of out-of-hospital cardiac arrest ranges from 37 to 46 per 100,000 events per year.1 Approximately 25% of all cardiac arrest patients are younger than 65 years of age.2 The favourable outcomes of patients who are admitted to the hospital range from 11% to 48%, indicating that a large number of patients die after successful resuscitation during their hospital stay or develop severe permanent neurological impairment.3, 4 The only therapy that has been shown to improve survival and neurological outcome after successful resuscitation from sudden cardiac arrest is the induction of mild therapeutic hypothermia for 12–24 h.5, 6Two large randomised clinical trials investigating the effect of mild hypothermia in cardiac arrest survivors only included patients with primary shockable cardiac rhythms.5, 6 There is a lack of data concerning the effect of mild therapeutic hypothermia in survivors after cardiac arrest with asystole or pulseless electrical activity as the first documented rhythms. Approximately 60–80% of patients who have suffered from an out-of-hospital cardiac arrest present with an initial non-shockable rhythm.4, 7, 8, 9 Some preliminary analyses have reported a non-significant reduction in unfavourable outcomes in patients who present with pulseless electrical activity or asystole and who were treated with mild hypothermia.10, 11, 12

The aim of this retrospective cohort study was to investigate the effect of mild therapeutic hypothermia on neurological outcome and mortality in patients who had been successfully resuscitated from non-ventricular fibrillation cardiac arrest.

Section snippets

Methods

This cohort study is based on a cardiac arrest registry that consists of all adult patients who were admitted to the department of emergency medicine of a tertiary-care hospital with cardiac arrest between January 1992 and October 2009. The institutional ethical review board has approved this registry. The data of all patients were prospectively documented according to the ‘Utstein Style Criteria’, which are the recommended guidelines for cardiac arrest and cardiopulmonary resuscitation outcome

Results

During an observational period from 1992 to 2009, 3391 patients with cardiac arrest were seen at the emergency department and documented in the registry. Out of these, 374 patients were analysed. The flow chart of case selection is shown in Fig. 1. Mild therapeutic hypothermia was induced in 135 patients. At baseline (Table 1), there were no statistically significant differences between the two groups except that there were less female patients in the group that was treated with hypothermia.

Discussion

Treatment with mild therapeutic hypothermia at temperatures between 32 °C and 34 °C for 24 h is associated with an improved neurological outcome and a reduced risk of death during a six-month observational period in patients who were successfully resuscitated from out-of-hospital cardiac arrests of non-traumatic origin with asystole or pulseless electrical activity as the first documented rhythm. This association remains unchanged after adjustment for confounders. The fact that patients with

Conclusion

Treatment with mild therapeutic hypothermia at a temperature of 32–34 °C for 24 h is associated with an improved neurological outcome and a reduced risk of death in patients following out-of-hospital cardiac arrest with an initial non-shockable rhythm. Nevertheless, the need for a prospective randomised clinical trial in this patient population to recommend the use of mild hypothermia after cardiac arrest is evident.

Conflict of interest statement

The authors declare that they have no financial and personal relationships with other people or organisations that could inappropriately influence (bias) their work.

Role of the funding source

There have been no study sponsors, who could have had a role in the study design, in the collection, analysis and interpretation of data; in the writing of the manuscript; and in the decision to submit the manuscript for publication.

Acknowledgements

We are indebted to the nurses and staff for their enthusiastic cooperation and to the patients who participated in this study for their trust and support.

References (26)

  • L.A. Cobb et al.

    Changing incidence of out-of-hospital ventricular fibrillation, 1980–2000

    JAMA

    (2002)
  • Hypothermia after Cardiac Arrest Study Group

    Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest

    N Engl J Med

    (2002)
  • S.A. Bernard et al.

    Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia

    N Engl J Med

    (2002)
  • Cited by (142)

    • Targeted Temperature Management and Postcardiac arrest Care

      2019, Emergency Medicine Clinics of North America
    View all citing articles on Scopus

    A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2011.05.022.

    View full text