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Hypothermia treatment does not help traumatic brain injury, study finds

BMJ 2018; 363 doi: (Published 24 October 2018) Cite this as: BMJ 2018;363:k4482
  1. Zosia Kmietowicz
  1. The BMJ

Brain cooling does not benefit people who have a brain injury, a randomised study has found, and it should no longer be used in this context, researchers have advised.1

Prophylactic hypothermia has been thought to help reduce the cerebral inflammatory and biochemical cascades associated with traumatic brain injuries and to improve neurological outcomes in patients, but evidence has been conflicting. A 2007 meta-analysis gave a low grade recommendation for using prophylactic hypothermia after severe traumatic brain injury, although the largest randomised controlled trial included in the review showed no benefit. And a trial this year found that hypothermia for more than 48 hours and slow rewarming improved survival.

To examine the clinical uncertainties around prophylactic hypothermia, researchers from Monash University in Melbourne, Australia, together with colleagues from five other centres, conducted the POLAR (prophylactic hypothermia to lessen traumatic brain injury) study.

They divided 511 patients with traumatic brain injury into two groups: half of the patients received hypothermia treatment (a bolus of 4°C saline and surface cooling wraps targeting a core temperature of 33°C-35°C for three to seven days) as soon as possible after injury, often in the ambulance on the way to the emergency department; and half did not receive this treatment.

The study ran for seven years from 2010 and is published in JAMA.1

Results showed that favourable outcomes at six months, as measured by the Glasgow Outcome Scale (Extended), occurred in 117 patients (48.8%) in the hypothermia group and in 111 (49.1%) in the normothermia group (risk difference 0.4% (95% confidence interval –9.4% to +8.7%); relative risk with hypothermia 0.99 (0.82 to 1.19); P=0.94). Pneumonia was more common in patients treated with hypothermia (55.0%) than in those not given this treatment (51.3%), as was intracranial bleeding (18.1% v 15.4%).

Limitations of the study included the fact that some patients in the hypothermia group did not reach the target temperature. Some were enrolled in the study before being properly evaluated so hypothermia was withdrawn, while others had unsurvivable injuries or were at risk of further intracranial bleeding.

Jamie Cooper, lead researcher and director of the Australian and New Zealand Intensive Care Research Centre, said that the study definitively found no benefit to patients from receiving hypothermia, as measured by their capacity to live independently after recovery from the injury. “This study is the final word on whether hypothermia as a treatment for traumatic brain injury works,” he said.

Using hypothermia in the intensive care unit requires valuable staff time and runs the risk of increased bleeding, infection, and decreased heart rate and blood pressure, all of which must be managed in vulnerable patients. “From now on, patients should not have to endure the risks of hypothermia because we now know there are no benefits,” said Cooper.

The study was supported by grants from the National Health and Medical Research Council of Australia, the Victorian Neurotrauma Initiative, the Teaching Hospital of Besançon in France, and the Health Research Board of Ireland Clinical Trial Network.


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