Background: The neuroprotective effects of hypothermia have been shown in case reports and animal studies. Therapeutic hypothermia is used to provide neuroprotection during certain types of surgery and after serious events that pose a threat to the brain. The aim of this review is to describe the efficacy of such treatment in adults.
Method: All articles retrieved from five searches in PubMed were examined. Studies were included if they had a hypothermia protocol and a measurement of neuroprotection. The list of randomised studies was completed using studies identified from five international review articles. In all, 103 of 678 studies fulfilled the inclusion criteria, of which 48 were clinical trials. Ten of the clinical trials were randomised, using a normothermic control group.
Results: Several randomised clinical trials have suggested that avoidance of hyperthermia provides the same neuroprotection as therapeutic hypothermia after cardiac arrest and traumatic brain injury, but prognostic factors and inclusion criteria vary markedly between the patient populations, including time to target temperature. Two studies found that cognitive function after prolonged aortic surgery under deep hypothermia was equivalent to that after brief normothermic interventions. Animal studies show a neuroprotective effect of hypothermia, but this is dependent on the extent of anoxic damage as well as the rate of cooling.
Interpretation: It remains uncertain how best to implement therapeutic hypothermia to achieve neuroprotection after acute events that pose a threat to the brain. Hypothermia during aortic surgery seems to provide adequate neuroprotection for prolonged interventions.