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Therapeutic hypothermia improves survival, reduces disability in neonates with hypoxic-ischemic encephalopathy, meta-analysis shows

Wednesday, March 03 2010 | Comments

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What's This? Among infants with hypoxic-ischemic encephalopathy (HIE), therapeutic hypothermia is associated with reductions in rates of mortality and neurological impairment at 18 months, according to findings of a meta-analysis.

Researchers identified trials that compared whole-body or selective head cooling versus normal care in neonates with HIE.

Data from 3 trials (n=767) showed that, relative to normal care, therapeutic hypothermia significantly reduced the risk of death or disability after >=18 months of follow-up (the primary outcome of the analysis), with a risk ratio (RR) of 0.81 (95% CI, 0.71-0.93; P=.002) and a number needed to treat (NNT) of 9 (95% CI, 5-25).

When infants with moderate and severe encephalopathy were evaluated separately, the benefit of hypothermia was statistically significant in the patients with moderate encephalopathy (RR, 0.73; P=.008), but not in those with severe encephalopathy (RR, 0.87; P=.07), although the test for an interaction effect was not significant (P=.18).

The analysis of these trials also showed that therapeutic hypothermia was associated with an increased rate of survival with normal neurological function (RR, 1.53 [95% CI, 1.22-1.93]; P<.001), with an NNT of 8 (95% CI, 5-17). In addition, hypothermia was associated with significant reductions in rates of severe disability (P=.006), cerebral palsy (P=.004), severe neurodevelopmental delay (P=.01), severe neuromotor delay (P=.02), and blindness (P=.03).

In an analysis of 10 trials (n=1,320) with mortality data, therapeutic hypothermia was associated with a significantly reduced risk of death during follow-up (RR, 0.78 [95% CI, 0.66-0.93]; P=.005), with an NNT of 14 (95% CI, 8-47). Among the patients in these trials, 169 of 660 hypothermia-treated infants died (26%), compared with 217 of 660 infants who received standard care (33%).

The current analysis provides the "highest level evidence that moderate hypothermia is efficacious in infants with HIE," the study authors wrote.

They added that the homogeneity of the trial results adds to the evidence of benefit, noting that the consistency of the findings is "particularly remarkable," given the differences among the studies in cooling methods and trial protocols.

"The minimal effect of these differences increases confidence that our findings can be generalized to the wider health care system and suggests that clinicians planning the widespread implementation of therapeutic hypothermia need be less concerned about the precise method of cooling and more focused on training of staff for its safe application," they wrote.

However, the investigators acknowledged that more research is necessary to determine the effect of therapeutic hypothermia on outcomes in later childhood. In addition, they cautioned that the current findings might not be generalizable to resource-poor environments. (Edwards AD, et al. BMJ 2010;340:c363.)

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