Clinical paperEfficacy of therapeutic hypothermia after out-of-hospital cardiac arrest due to ventricular fibrillation☆
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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Mechanical circulatory support
2014, Emergency Medicine Clinics of North America
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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.