Background Hypothermia has been used in the treatment of head injury for many years. Encouraging results from small trials and laboratory studies led to renewed interest in the area and some larger trials. Objectives To estimate the effect of mild hypothermia for traumatic head injury on mortality and long-term functional outcome complications. Search strategy We searched the Injuries Group Specialised Register, Current Controlled Trials MetaRegister of trials, Zetoc, Web of Knowledge; Science Citation Index [expanded], CENTRAL, MEDLINE and EMBASE. We handsearched conference proceedings and checked reference lists of relevant articles. The search was updated on 23 May 2008. Selection criteria Randomised controlled trials of hypothermia to a maximum of 35ºC for at least 12 hours versus control in patients with any closed traumatic head injury requiring hospitalisation. Two authors independently assessed all trials. Data collection and analysis Data on death, Glasgow Outcome Scale and pneumonia were sought and extracted, either from published material or by contacting the investigators. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each trial on an intention-to-treat basis. Main results We found 22 trials with a total of 1409 randomised patients. Twenty trials involving 1382 patients reported deaths. There were fewer deaths in patients treated with hypothermia than in the control group (OR 0.76, 95% CI 0.60 to 0.97). Eight trials with good allocation concealment showed a non-significant reduction in the likelihood of death for patients treated with hypothermia (OR 0.96, 95% CI 0.68 to 1.35). Twenty trials involving 1382 patients reported data on unfavourable outcomes (death, vegetative state or severe disability). Patients treated with hypothermia were less likely to have an unfavourable outcome than those in the control group (OR 0.69, 95% CI 0.55 to 0.86). Eight trials with good allocation concealment showed a non-significant reduction in the likelihood of unfavourable outcome for patients treated with hypothermia (OR 0.79, 95% CI 0.57 to 1.08). Hypothermia treatment was associated with an increase in odds of pneumonia but this increase was not statistically significant for trials with good allocation concealment (3 trials, 69 patients, OR 1.06, 95% CI 0.38 to 2.97).
