Rapid Induction of Brain Hypothermia by Selective Intra-Arterial Perfusion of Crystalloid Solution in an Animal Model

We have developed an extracorporeal cooling-filtration system for rapid induction of brain hypothermia, and have investigated the safety and feasibility of this system in an animal model. Ringer’s solution cooled to 7°C was perfused at a rate of 3 ml/kg per minute for 30 min into the right common carotid artery through an angiographic catheter in five adult canines (weight 13.06 ± 1.84kg). Excessive fluid was ultrafiltrated through a femoral venovenous extracorporeal circuit. Temperature was monitored in the cerebral hemispheres and the rectum. Blood samples were obtained from the right jugular vein. Brain tissue oxygen tension was measured in the right frontal lobe in three cases. The right brain temperature decreased to 33.9 ± 2.0°C from 37.8 ± 1.4°C 30 min after initiation of perfusion, while left brain and rectal temperatures were 34.6 ± 1.6°C and 34.3 ± 1.4°C, respectively. The cooling rate of the right cerebral hemisphere (3.9 ± 0.8°C/30min) was advanced significantly more than those of the rectum (2.7 ± 0.4°C/30min, P < 0.01) and the left cerebral hemisphere (3.2 ± 0.4°C/30 min, P < 0.05). Jugular venous saturation increased during perfusion, although jugular venous hemoglobin and hematocrit decreased at the same time. Brain tissue oxygen tension was 110%, 105%, and 99% of precooling values 30 min after perfusion. Animals were rewarmed and awakened without neurological deficits. This study demonstrated that the extracorporeal cooling-filtration system safely and rapidly induced brain hypothermia. This method may be potentially combined with endovascular surgery or therapy.