Resuscitation Science Is Hypothermia After Cardiac Arrest Effective in Both Shockable and Nonshockable Patients? Insights From a Large Registry

Background—Although the level of evidence of improvement is significant in cardiac arrest patients resuscitated from a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia [VF/VT]), the use of therapeutic mild hypothermia (TMH) is more controversial in nonshockable patients (pulseless electric activity or asystole [PEA/ asystole]). We therefore assessed the prognostic value of hypothermia for neurological outcome at hospital discharge according to first-recorded cardiac rhythm in a large cohort. consecutive out-of-hospital cardiac arrest patients in whom a successful resuscitation had been achieved were prospectively collected. The association of TMH with a good neurological outcome at hospital discharge (cerebral performance categories level 1 or 2) was quantified by logistic regression analysis. TMH was induced in 457/708 patients (65%) in VF/VT and in 261/437 patients (60%) in PEA/asystole. Overall, 342/1145 patients (30%) reached a favorable outcome (cerebral performance categories level 1 or 2) at hospital discharge, respectively 274/708 (39%) in VF/VT and 68/437 (16%) in PEA/asystole (PϽ0.001). After adjustment, in VF/VT patients, TMH was associated with increased odds of good neurological outcome (adjusted odds ratio, 1.90; 95% confidence interval, 1.18 to 3.06) whereas in PEA/asystole patients, TMH was not significantly associated with good neurological outcome (adjusted odds ratio, 0.71; 95% confidence interval, 0.37 to 1.36). Conclusions—In this large cohort of cardiac arrest patients, hypothermia was independently associated with an improved outcome at hospital discharge in patients presenting with VF/VT. By contrast, TMH was not associated with good outcome in nonshockable patients. Further investigations are needed to clarify this lack of efficiency in PEA/asystole. E ach year, at least 225 000 new out-of-hospital cardiac arrests (OHCA) occur in Europe and in the US. 1,2 Even after a successful resuscitation and transportation procedure, survival rates to hospital discharge of these patients remain low, ranging from 21% to 33%. 3–5 The poor prognosis of these patients in whom the return of spontaneous circulation (ROSC) has been initially achieved is attributed to postcar-diac arrest syndrome, which is the combination of postcardiac brain injury, circulatory dysfunction, and systemic ischemia/ reperfusion response. 6 Animal studies 7–9 have demonstrated that hypothermia is able to decrease the consequences of the anoxo-ischemic neurological injury that follows the cerebral reperfusion. In the last decade, 2 randomized clinical trials 10,11 and a meta-analysis 12 have confirmed the benefit in OHCA comatose survivors cooled within the minutes or hours after initial resuscitation from an out-of-hospital ventricular fibrillation (VF). As a consequence, the most recent guidelines …