Mild therapeutic hypothermia in patients resuscitated from out-of-hospital cardiac arrest: A meta-analysis of randomized controlled trials

Abstract

Aims: Guidelines recommend mild therapeutic hypothermia (MTH) for survivors of out-of-hospital cardiac arrest (OHCA). However, there is little literature demonstrating a survival benefit. We performed a meta-analysis of randomized controlled trials (RCTs) assessing the efficacy of MTH in patients successfully resuscitated from OHCA.

Materials and methods: Electronic databases were searched for RCT involving MTH in survivors of OHCA, and the results were put through a meta-analysis. The primary endpoint was all-cause mortality, and the secondary endpoint was favorable neurological function. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using the Mantel-Haenszel method. A fixed-effect model was used and, if heterogeneity (I2 ) was >40, effects were analyzed using a random model.

Results: Six RCT (n = 1400 patients) were included. Overall survival was 50.7%, and favorable neurological recovery was 45.5%. Pooled data demonstrated no significant all-cause mortality (OR, 0.81; 95% CI 0.55-1.21) or neurological recovery (OR, 0.77; 95% CI 0.47-1.24). No evidence of publication bias was observed.

Conclusion: This meta-analysis demonstrated that MTH did not confer benefit on overall survival rate and neurological recovery in patients resuscitated from OHCA.

Figure 1

Search Strategy and Study Selection. RCT = Randomized Controlled Trial MTH = Mild therapeutic hypothermia

Figure 2

All-cause mortality. Comparison of all-cause mortality outcome between patients treated with MTH and the control group using a random model. Heterogeneity (I²) = 41.4%. CI = Confidence interval; MH = Mantel-Haenszel; MTH = Mild therapeutic hypothermia

Figure 3

Favorable neurological outcomes. Comparison of favorable neurological outcome between patients treated with MTH and the control group using a random model. Heterogeneity (I²) = 56.2%. CI = Confidence interval; MH = Mantel-Haenszel; MTH = Mild therapeutic hypothermia

Figure 4

Funnel plots for each individual outcome: (a) All-cause mortality; table (b) favorable neurological outcomes. Randomized controlled trials are shown as open circles and the observed summary point estimate in log units is shown as an open diamond. The imputed studies are shown as a filled circle, and the imputed point estimate in log units is shown as a filled diamond, No imputed studies were seen for overall mortality. Two imputed studies were seen for favorable neurological outcomes. Under the random effect model the point estimate and 95% confidence interval for the combined studies is 0.78 (0.73, 0.83). Using trim and fill, the imputed point estimate is 0.77 (0.72, 0.82)