Controlled brain hypothermia by extracorporeal carotid blood cooling at normothermic trunk temperatures in pigs

Cerebral hypothermia improves outcomes after brain injury. A technique is presented for isolated brain cooling in pigs by cooling the natural blood supply of the brain. Under general anesthesia both common carotid arteries were exteriorized. One proximal carotid artery was connected to both distal carotid arteries and a heat exchanger in this line controlled brain temperature. The second proximal carotid artery was connected to an external jugular vein and a heat exchanger in this arteriovenous shunt was used to clamp trunk temperature. Thalamic brain temperatures of anesthetized juvenile pigs (N = 8) were clamped at 38, 25, and 30 degrees C while trunk core temperature was clamped at 38 degrees C. Approximately 7 min were needed to decrease brain temperature from 38 to 25 degrees C, reducing brain electric activity by 76% and increasing the temperature differences between different brain sites. Mean arterial blood pressure, heart rate, and cardiac output showed no significant change. Re-establishment of normothermic brain temperature led to a virtually complete recovery of brain electric activity. The technique is suitable for investigations of ischemic and traumatic injuries.