Therapeutic hypothermia reduces risk of death and disability in infants with hypoxic-ischaemic encephalopathy, according to a new study by David Edwards and colleagues published in the British Medical Journal.
Hypoxic-ischaemic encephalopathy (damage to cells in the brain and spinal cord because of lack of oxygen) is a major cause of death and disability worldwide but there currently is no specific treatment available for it. Therapeutic hypothermia (cooling the body below the normal temperature of 37oC) has been reviewed previously and tested in several clinical trials for newborns with hypoxic-ischemic encephalopathy but the results have so far been inconclusive and consensus in the medical profession has not been reached.
Edwards and colleagues carried out a meta-analysis which took advantage of new studies, including results from the TOBY trial, and recently available additional data from previously reported studies to determine whether moderate hypothermia after hypoxic-ischemia encephalopathy in newborns improves survival and neurological outcome 18 months later.
The researchers analysed data from 1320 infants in 10 different randomised controlled trials (studies which reported at least mortality data). They also assessed data from a subset of three trials which had similar entry requirements—evidence of oxygen deprivation of birth and moderate and severe encephalopathy— which investigated neurological outcomes up to 18 months of age in 767 infants.
The investigators found that therapeutic hypothermia significantly reduced the combined death and severe disability rates in the subset of three trials with outcome data at 18 months. Cooling newborns deprived of oxygen at birth not only increased survival with normal neurological function but also reduced the rates of severe disability, cerebral palsy, severe neuromotor delay, severe neurodevelopmental delay and blindness. They observed no association between the severity of encephalopathy and the effect of cooling treatment. In their analysis of all the 10 different trials, the researchers showed that hypothermia therapy significantly reduced mortality.
“In the absence of any specific intervention to improve the dismal prognosis of infants with hypoxic-ischaemic encephalopathy, clinical enthusiasm for a novel treatment is understandable,” write the investigators, “this new meta-analysis … provides the highest level evidence that moderate hypothermia is efficacious in infants with hypoxic-ischaemic encephalopathy”. More work is needed to follow up the infants enrolled in these therapeutic hypothermia studies to determine whether they continue to reap the benefits of cooling therapy in later childhood.
Edwards, A., Brocklehurst, P., Gunn, A., Halliday, H., Juszczak, E., Levene, M., Strohm, B., Thoresen, M., Whitelaw, A., & Azzopardi, D. (2010). Neurological outcomes at 18 months of age after moderate hypothermia for perinatal hypoxic ischaemic encephalopathy: synthesis and meta-analysis of trial data BMJ, 340 (feb09 3) DOI: 10.1136/bmj.c363