Objective: We investigated the possibility of differential brain cooling by an endovascular method, perfusing cooled crystalloid solution transarterially.
Methods: Fifteen healthy adult hybrid dogs were divided into three groups according to different crystalloid infusion rates: Group 1 received 1.5 ml/kg/min (n=6), Group 2 received 3.0 ml/kg/min (n=6) and Group 3 received 5.0 ml/kg/min (n=3). A four-French angiographic catheter was placed into the right common carotid artery to infuse cooled Ringer's solution. A six-French angiographic catheter was placed into the right jugular vein to withdraw hemodiluted blood. Excessive fluid was eliminated using a dialyzer in a venovenous extracorporeal circuit. Hypothermic perfusion was continued for 30 minutes. A Swan-Ganz catheter was inserted to measure cardiac output. Temperatures were monitored in the cerebral hemispheres and rectum.
Results: The cooling rates of the right cerebral hemisphere were 1.8 +/- 0.9 degrees C/30 min in Group 1 and 4.7 +/- 1.0 degrees C/30 min in Group 2. The cooling rates of the left cerebral hemisphere and rectum were 1.4 +/- 0.5 and 1.5 +/- 0.7 degrees C/30 min in Group 1, and 3.5 +/- 0.5 and 3.4 +/- 0.8 degrees C/30 min in Group 2, respectively. In Group 3, two dogs died after the experiment. Systemic hemodynamics was stable throughout the experiment in Group 1, while arterial blood pressure, heart rate and cardiac output changed significantly after perfusion in Group 2.
Conclusion: Transarterial perfusion of cooled crystalloid solution achieved differential cooling between the target and other sites. However, the difference was small and further refinements are necessary to achieve beneficial effects.