Elsevier

Resuscitation

Volume 75, Issue 2, November 2007, Pages 252-259
Resuscitation

Clinical paper
Efficacy of therapeutic hypothermia after out-of-hospital cardiac arrest due to ventricular fibrillation

https://doi.org/10.1016/j.resuscitation.2007.04.014Get rights and content

Summary

Aim of the study

We investigated implementation and efficacy of mild therapeutic hypothermia in the treatment of out-of-hospital cardiac arrest due to ventricular fibrillation.

Materials and methods

Two periods were compared, an historical one (36 patients) between 2000 and 2002 where therapeutic hypothermia was never used, and a recent period (32 patients) between 2003 and 2005 where therapeutic hypothermia (32–34 °C) was implemented prospectively in our unit. Cooling was obtained by simply using wet cloths and ice packs. Survival in the two groups and factors associated with survival were analysed, together with the neurological prognosis in discharged patients.

Results

Survival was significantly higher in the hypothermia group (56% versus 36%), whereas no significant difference was observed in severity between the two periods. Only age, time from return to spontaneous circulation <20 min, and therapeutic hypothermia were independently associated with survival. Therapeutic hypothermia was well tolerated and was associated with a significant improvement in neurological outcome. Whereas only 23% of patients actually reached the target temperature in 2003, 100% did in 2005.

Conclusion

Therapeutic hypothermia is efficient in significantly improving survival and neurological outcome of out-of-hospital cardiac arrest with ventricular fibrillation. By using a simple method, it can be implemented easily and quickly, without side effects.

Introduction

Annually there are around 30,000–50,000 out-of-hospital sudden deaths due to cardiac arrest in France and 350,000 in Europe.1 Mortality is high and depends on the initially observed cardiac rhythm. Mortality in patients with asystole has been reported to be as high as 95%,2, 3 but some studies suggest a better prognosis for ventricular fibrillation, with 25–30% recovery.4 Furthermore, neurological recovery without sequelae is not uncommon, and in one study severe neurological damage has been observed in approximately 64% of patients who finally recover.5

After initial resuscitation, a number of mechanisms are directly responsible for cerebral damage, multi-organ failure, and finally death.6 These include initial ischemia, reperfusion injury, with free radical production, inflammation, mitochondrial dysfunction and excitatory cascade, secondary global hypoperfusion with multi-focal no reflow, and hypercoagulability.7, 8 For a long time, experimental studies have suggested that hypothermia could affect many of these mechanisms9 and protect the brain by reducing cerebral metabolism and oxygen consumption.10 This has led to the concept of neuroprotection.

Recently, two prospective, randomised studies, in patients with out-of-hospital cardiac arrest caused by ventricular fibrillation, have reported that therapeutic hypothermia (TH) decreases mortality and improves cerebral prognosis.[11], 12 In an observational study, Sunde et al. have also suggested the potential efficacy of such a procedure.13 However, implementation of TH remains problematical,14, 15 partly because of lack of data, and also because physicians feel that inducing cooling is technically difficult.14 A recent European study on the feasibility of TH reported that TH was not used in nearly 40% of cases of cardiac arrest.16 A recent study has even suggested the absence of any beneficial effect of TH.17

In 2003, we decided to use TH systematically in patients admitted to our intensive care unit (ICU) after out-of-hospital cardiac arrest with ventricular fibrillation. The aim of our study firstly is to report the impact of this protocol on survival and on neurological outcome, by comparing a recent period to an historical one, and secondly to describe the implementation and side effects of such a protocol. Our study was approved by the Ethics Committee of Ambroise Paré Hospital.

Section snippets

Study design

The study was conducted in a 9-bed medical ICU of a university hospital of 500 beds between January 2000 and December 2005. The study population consisted of all consecutive patients resuscitated successfully following out-of-hospital cardiac arrest and admitted to our hospital. The criteria for inclusion were a witnessed arrest, ventricular fibrillation as the initial rhythm, whatever its cause, comatose patients, intubated and mechanically ventilated at their admission to our ICU, and an age

Results

During the study period, 200 patients were hospitalised in our unit after an out-of-hospital cardiac arrest, 76 related to ventricular fibrillation. Among the 76 patients, 8 moribund patients were excluded from the analysis, 4 before 2003 and 4 after, thus leading to a population of 68 patients. Thirty-six patients were analysed in the historical group and 32 in the hypothermia group. As shown in Table 1, Table 2, the baseline characteristics of the patients at admission, as well as the

Discussion

By comparing two periods, one historical where TH was never used, and the other in which TH was systematically applied, we report a large improvement in survival in patients with out-of-hospital cardiac arrest related to ventricular fibrillation. The survival rate increased from 36% in the historical group to 56% in the hypothermia group. Whereas the study was not a randomised one, patients were strictly checked for most of the usual criteria of severity, and there was no significant difference

Conclusion

Our study demonstrates that therapeutic hypothermia improves survival significantly following out-of-hospital cardiac arrest with ventricular fibrillation. By using a simple method of cooling, it can be implemented easily and quickly, without serious side effects.

Conflict of interest

The authors declare no conflict of interest.

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    A Spanish translated version of the summary of this article appears as Appendix in the final online version at 10.1016/j.resuscitation.2007.04.014.

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