Hypothermia in patients with brain injury: the way forward?

Abstract

In the National Acute Brain Injury Study: Hypothermia II (NABIS: H II), reported by Guy Clifton and colleagues, the target temperature of 33°C was reached in 4·4 h, and patients in the hypothermia group were cooled for 48 h and then rewarmed by 0·5°C every 2 h. As a result, hypothermia did not improve outcome in these patients. We agree with Maas and Stocchetti that a period of 48 h of hypothermia might be too short to have a benefi cial eff ect on outcome. We would like to emphasise that the rate of rewarming is also an important variable that infl uences the protective eff ects of hypothermic intervention after traumatic brain injury. Povlishock and Wei’s review showed that hypothermia followed by rapid rewarming not only reversed the protective eff ects associated with hypothermic intervention but also, in some cases, exacerbated the traumatically induced pathology and its functional consequences. Suehiro and Povlishock have shown that rapid rewarming could exacerbate the progression of traumatically induced axonal change in a rat model. Whether rewarming patients by 0·5°C every 2 h was appropriate is not clear, because the optimum rate is unknown. Reported rates of rewarming range from 0·5°C every 2 h to 1°C per day. However, we believe that a slower rewarming might be a better therapeutic strategy.