The effects of 30% and 60% xenon inhalation on pial vessel diameter and intracranial pressure in rabbits.

UNLABELLED: Xenon may increase cerebral blood flow and intracranial pressure (ICP). To evaluate the effects of xenon on brain circulation, we measured pial vessel diameter changes, CO(2) reactivity, and ICP during xenon inhalation in rabbits. Minimum alveolar anesthetic concentration (MAC) for xenon was established in rabbits (n = 6). By using a cranial window model, pial vessel diameters were measured at 30% and 60% xenon inhalation and in time control groups (n = 15). ICP, mean arterial blood pressure, and heart rate were recorded during 30% and 60% xenon inhalation (n = 5). Pial vessel diameters were measured during hypocapnia and hypercapnia conditions in 60% Xenon and Control groups (n = 14). MAC for xenon was 85%. Xenon (0.35 and 0.7 MAC) dilated the arterioles (10% and 18%, respectively) and venules (2% and 4%, respectively) (P < 0.05). Dilation of arterioles was more prominent than that of venules. ICP, mean arterial blood pressure, and heart rate did not change during xenon inhalation. No difference in CO(2) reactivity was observed between Xenon and Control groups (P = 0.79). Sixty percent xenon (0.7 MAC) dilated brain vessels, but venule changes were small. Xenon did not increase ICP and preserved CO(2) reactivity of the brain vessels. IMPLICATIONS: Xenon might increase cerebral blood flow; however, 0.7 minimum alveolar anesthetic concentration xenon preserved both low intracranial pressure and CO(2) reactivity of the cerebral vessels in the normal rabbit.