Effect of 35°C Hypothermia on Intracranial Pressure and Clinical Outcome in Patients With Severe Traumatic Brain Injury

Abstract

From 1994, we have used therapeutic hypothermia in patients with severe traumatic brain injury (Glasgow Coma Scale scores of 5 or less). In 2000, we altered the target temperature to 35°C from the former 33°C, as our findings suggested that cooling to 35°C is sufficient to control intracranial hypertension, and that hypothermia below 35°C may predispose patients to persistent cumulative oxygen debt. We attempted to clarify whether 35°C hypothermia has the same effect as 33°C hypothermia in reducing intracranial hypertension and whether it is associated with fewer complications and improved outcomes.

We compared intracranial pressure (ICP) and biochemical parameters in the 30 patients treated with 35°C hypothermia (January 2000 to June 2005) with those in the 31 patients treated with 33°C hypothermia (July 1994 to December 1999).

Patient characteristics were similar in the two groups. The mean temperature during hypothermia was 35.1 ± 0.7°C in the 35°C hypothermia group and 33.4 ± 0.8°C in the 33°C hypothermia group. Mean ICP was controlled under 20 mm Hg during hypothermia in both the 35°C hypothermia and 33°C hypothermia groups. The incidence of intracranial hypertension and low cerebral perfusion pressure did not differ between the two groups. The 35°C hypothermic patients exhibited a significant improvement in the decline of serum potassium concentrations during hypothermia and in the increment of C-reactive protein after rewarming. The mortality rate and the incidence of systemic complications tended to be lower in the 35°C group.

Cooling patients to 35°C is safe and the ICP reduction effects of 35°C hypothermia are similar to those of 33°C hypothermia.