Systemic hypothermia in treatment of brain injury

An extensive literature suggests that there are minimal complications of systemic hypothermia in humans at and above 30°C for periods of several days. Intracranial hemorrhage has been found to complicate profound hypothermia (10-15°C), and ventricular arrhythmias occur at temperatures below 30°C. Our initial clinical studies were with 21 patients undergoing elective craniotomy cooled to 30-32°C for 1-8 h (mean 4 h). Hypothermia was induced by surface cooling with water blankets. No complications were found. Among 11 patients with severe brain injury, cooling to levels below 32°C was associated with ventricular arrhythmias in 1 patient and atrioventricular block in 1 patient. Asymptomatic hypokalemia was found routinely and treated with potassium replacement. No intracranial hemorrhage or other complications were found. With surface cooling, intravascular temperature dropped at 1.6°C/h. Based on the safety of surface cooling to a core temperature of 32°C for 48 h, we are conducting a randomized study of this level of hypothermia in patients with severe brain injury, cooled within 6 h of injury.