Background: The neuroprotective effects of cooling the spinal cord in a sheep model by a self-contained intrathecal catheter was reported recently by the authors. The present study was designed to determine if cooling catheters in the lateral ventricles of the brain can effectively cool the CSF and thereby reduce brain temperature while maintaining systemic normothermia.
Methods: The cooling catheter is a self-contained system that circulates a cold fluid and cools the CSF that circulates in the brain. The CSF in turn cools the surrounding brain by conduction. Burr holes were made in the skull and the catheter was placed into the lateral ventricles using the standard method for placement of ventriculostomy catheters. To monitor the cooling effect, four temperature probes were placed in the brain (left and right hemispheres of the brain in anterior and posterior locations to the ventricles).
Results: Five experiments were successfully completed. The mean brain temperature for all sheep decreased to 34.5°C (mean) during the 3 h cooling period (9.7% reduction from baseline brain temperature of 38.2°C). Cooling fluid was circulated through the catheter at a rate of 50 ml/min. The lowest achieved brain temperature during cooling was 26.7°C. When cooling was stopped, the brain temperature readings equilibrated with the core temperature promptly. Post mortem examination of the brains showed no morphologic changes under gross or histologic examinations.
Conclusion: Localized cooling of the brain to moderate hypothermic levels while maintaining relative systemic normothermia was demonstrated in an animal model with intraventricular cooling catheters.