Five RCTs (n=552) were included in the review.
All studies used appropriate allocation concealment and randomisation methods. Two studies blinded the outcome assessment and three reported adequate follow-up (93 to 98%).
Therapeutic hypothermia reduced the composite outcome of death or disability (RR 0.78, 95% CI: 0.66, 0.92; NNT 6, 95% CI: 5, 20; 5 RCTs, n=552). Mortality was also significantly lower in the hypothermia group (RR 0.75, 95% CI: 0.59, 0.96; NNT 11, 95% CI: 6, 100). The subgroup analysis revealed that there was a significant effect for the study using whole body cooling (RR 0.68, 95% CI: 0.48, 0.97; NNT 8, 95% CI: 5, 100; 3 RCTs), but not for the 2 RCTs using selective head cooling.
There was a significant effect of hypothermia on overall neurodevelopmental disability at ≥18 months of age (3 RCTs, n=449), but not on disabling cerebral palsy, developmental delay, blindness or loss of hearing (3 RCTs in each case). No statistically significant heterogeneity between the studies was reported.
Significant adverse events were sinus bradycardia (RR 7.42, 95% CI: 2.52, 21.87; NNH 13, 95% CI: 8, 20; 4 RCTs), thrombocytopenia (RR 1.47, 95% CI: 1.07, 2.03; NNH 8, 95% CI: 5, 50; 3 RCTs) and spontaneously resolved higher mean plasma glucose concentrations. There were no other significant differences in adverse events.