Meta-Analysis of the Usefulness of Therapeutic Hypothermia After Cardiac Arrest

Abstract

Despite current guidelines recommending therapeutic hypothermia (TH) for post cardiac arrest comatose patient, its use remains limited. Randomized controlled trials (RCTs) have also reported conflicting results on the efficacy of TH. Therefore, we conducted an updated meta-analysis to evaluate the effect of TH in post cardiac arrest patients. We searched electronic databases for RCTs comparing TH (32°C to 34°C) with controls (normothermia or temperature ≥36°C) in comatose patients who sustained cardiac arrest. Mortality and neurological outcomes were the outcomes of interest. We used random effect meta-analysis to estimate risk ratio (RR) with 95% confidence interval (CI). Eight RCTs with a total of 2,026 patients (TH n = 1,025 and control n = 1,001) were included. Irrespective of initial rhythm, TH was associated with significant reduction in poor neurological outcomes (RR 0.87, 95% CI 0.77 to 0.98; p = 0.02) without any difference in mortality (RR 0.94, 95% CI 0.85 to 1.03; p = 0.17). In patients with initial shockable rhythm compared with control, TH reduced mortality (RR 0.85, 95% CI 0.73 to 0.99; p = 0.04) and poor neurological outcomes (RR 0.81, 95% CI 0.67 to 0.99; p = 0.04). Whereas, in patients with initial nonshockable rhythm, TH was associated with decreased poor neurological outcomes after excluding one trial (RR 0.95 95% CI 0.91 to 1.00; p = 0.05). In conclusion, TH is associated with improved neurological outcomes in all patients sustaining cardiac arrest and with decreased mortality in patients with initial shockable rhythm.