Cerebral Blood Flow and Metabolism during Mild Hypothermia in Patients with Severe Traumatic Brain Injury

Cerebral blood flow (CBF) measurements during mild hypothermia therapy were made in 30 adult patients with severe head injuries (Glasgow Coma Scale score ≦8), by xenon enhanced computed tomography (Xe-CT). All patients but one underwent removal of hematomas and decompressive craniectomy. Immediately after surgery, hypothermia was induced by surface cooling, and a brain temperature of 32 - 35℃ was maintained for 3 days. During hypothermia therapy, CBF measurements by Xe-CT were made for all patients on post-injury days 1 to 4. From the arteriovenous-oxygen content difference and CBF values, the cerebral metabolic rate of oxygen (CMRO2) values were obtained. Outcome was assessed at discharge according to the patients’ Glasgow Outcome Scale (GOS) scores. Patients were divided into two groups based on their outcomes. Nineteen patients (63%) showed good outcomes (GOS score of 4 or 5) and 11 (37%) showed poor outcomes (GOS score of 1, 2, or 3). Statistically significant differences were obtained for the mean global CBF and CMRO2 values between the good and poor outcome groups. In this study, we demonstrated that CBF measurement may be useful to predict neurological outcomes following severe traumatic brain injury in patients undergoing hypothermia as well as to identify those who might not likely benefit from hypothermia therapy