A novel selective cooling system for the brain: feasibility study in rabbits vs piglets.

BACKGROUND: Selective brain cooling (SBC) methods could alleviate the complications associated with systemic hypothermia. The authors (MFB, LK, and T-YL) have developed a simple and an effective nasopharyngeal SBC method using a vortex tube. The primary focus of the study is to evaluate the effectiveness of this approach on rabbits and compare it with our previous published finding on piglets, which are mammals without and with a carotid rete, respectively.

METHODS: Experiments were conducted on six rabbits. Body temperature was measured continuously using an esophageal temperature probe while brain temperature was measured with an implanted thermometer. Two successive experiments were performed on each animal. In the first experiment, brain cooling was initiated by blowing room temperature air from the hospital medical air outlet, at a flow rate of 14-15 L/min into both nostrils for 60 min. The second series of measurements and brain cooling was performed in the same manner as the first one but blowing cold air (- 7 °C) at the same flow rate.

RESULTS: One hour post cooling with room temperature air at a flow rate of 14-15 L/min, the brain temperature was 34.2 ± 1.2 °C which resulted in mean brain cooling rates of 3.7 ± 0.9 °C/h. Brain temperature could be reduced more rapidly at mean rates of 5.2 ± 1.9 °C/h, while the body temperature as measured by the esophageal temperature probe was maintained above 36 °C during cooling and maintaining period.

CONCLUSIONS: We have demonstrated that using the vortex tube allows initial rapid and SBC in rabbits. Moreover, comparing results between piglets and rabbits demonstrates clearly that the lack of a carotid rete does not prevent specific cooling of the brain by means of the nasopharyngeal method.