Differences in patient characteristics and care practices between two trials of therapeutic hypothermia

The Induced Hypothermia (IH) and Optimizing Cooling (OC) trials for hypoxic-ischemic encephalopathy (HIE) had similar inclusion criteria. The rate of death/moderate-severe disability differed for the subgroups treated with therapeutic hypothermia (TH) at 33.5 °C for 72 h (44% vs. 29%, unadjusted p = 0.03). We aimed to evaluate differences in patient characteristics and care practices between the trials.

We compared pre/post-randomization characteristics and care practices between IH and OC.

There were 208 patients in the IH trial, 102 cooled, and 364 in the OC trial, 95 cooled to 33.5 °C for 72 h. In OC, neonates were less ill, fewer had severe HIE, and the majority were cooled prior to randomization. Differences between IH and OC were observed in the adjusted difference in the lowest PCO₂ (+3.08 mmHg, p = 0.005) and highest PO₂ (-82.7 mmHg, p < 0.001). In OC, compared to IH, the adjusted relative risk (RR) of exposure to anticonvulsant prior to randomization was decreased (RR 0.58, (0.40-0.85), p = 0.005) and there was increased risk of exposure during cooling to sedatives/analgesia (RR 1.86 (1.21-2.86), p = 0.005).

Despite similar inclusion criteria, there were differences in patient characteristics and care practices between trials. Change in care practices over time should be considered when planning future neuroprotective trials.