The role of hypothermia in the management of severe brain injury. A meta-analysis

Context: Hypothermia is utilized in the management of severe traumatic brain injury despite the lack of unequivocal evidence supporting its use. Because of its widespread use, the effects of hypothermia are a concern. Objective: To determine the effectiveness of hypothermia in the management of severe brain injury. Data Sources: Two investigators working independently abstracted data in a blinded fashion from studies identified using multiple literature databases, including MEDLINE, Ovid, PubMed, the Cochrane Database of Systematic Reviews, EMBASE, and the abstract center for the American Association of Neurological Surgery and the Congress of Neurological Surgery, as well as the bibliographies of these articles. Additionally, experts in the field of hypothermia and neurotrauma provided additional references. Study Selection: Seven studies met predetermined inclusion criteria: (1) the study was a randomized clinical trial comparing the efficacy of hypothermia vs normothermia in patients with posttraumatic head injury, (2) only subjects aged 10 years or older were included in the study, and (3) relative risks (odds ratios [ORs], cumulative incidence, or incidence density measures) and 95% confidence intervals (CIs) or weighted mean differences and 95% CIs could be calculated from the data presented in the article. These criteria were applied in a blinded fashion by 2 independent investigators. Data Extraction: No single outcome variable was evaluated in all studies. The following outcome variables were assessed: intracranial pressure, Glasgow Outcome Scale score, pneumonia, cardiac arrhythmia, prothrombin time, and partial thromboplastin time. Either ORs or weighted mean differences (when the data provided did not permit calculation of an OR) comparing the effects of hypothermia vs normothermia were calculated from the data provided. Data Synthesis: The weighted mean difference (hypothermia-normothermia) for intracranial pressure was -2.98 mm Hg (95% CI, -7.58 to 1.61; P=.2). The OR (hypothermia vs normothermia) for Glasgow Outcome Scale score was 0.61 (95% CI, 0.26-1.46; P=.3). The OR for pneumonia was 2.05 (95% CI, 0.79-5.32; P=. 14). The OR for cardiac arrhythmia was 1.27 (95% CI, 0.384.25; P=.7). The weighted mean difference for prothrombin time was 0.02 seconds (95% CI, -0.07 to 0.10; P=.7). The weighted mean difference for partial thromboplastin time was 2.22 seconds (95% CI, 1.73-2.71; P <.001). Conclusions: This meta-analysis of randomized controlled trials suggests that hypothermia is not beneficial in the management of severe head injury. However, because hypothermia continues to be used to treat these injuries, additional studies are justified and urgently needed.