Isoflurane lowers the cerebral metabolic rate of oxygen and prevents hypoxia during cortical spreading depolarization <i>in vitro</i> : An integrative experimental and modeling study
Karl Schoknecht, Mathilde Maechler, Iwona Wallach, Jens P. Dreier, Agustin Liotta, Nikolaus Berndt
Abstract
Cortical spreading depolarization (SD) imposes a massive increase in energy demand and therefore evolves as a target for treatment following acute brain injuries. Anesthetics are empirically used to reduce energy metabolism in critical brain conditions, yet their effect on metabolism during SD remains largely unknown. We investigated oxidative metabolism during SD in brain slices from Wistar rats. Extracellular potassium ([K + ] o ), local field potential and partial tissue oxygen pressure (p ti O 2 ) were measured simultaneously. The cerebral metabolic rate of oxygen (CMRO 2 ) was calculated using a reaction-diffusion model. By that, we tested the effect of clinically relevant concentrations of isoflurane on CMRO 2 during SD and modeled tissue oxygenation for different capillary pO 2 values. During SD, CMRO 2 increased 2.7-fold, resulting in transient hypoxia in the slice core. Isoflurane decreased CMRO 2 , reduced peak [K + ] o , and prolonged [K + ] o clearance, which indicates reduced synaptic transmission and sodium-potassium ATPase inhibition. Modeling tissue oxygenation during SD illustrates the need for increased capillary pO 2 levels to prevent hypoxia. In the absence thereof, isoflurane could improve tissue oxygenation by lowering CMRO 2 . Therefore, isoflurane is a promising candidate for pre-clinical studies on neuronal survival in conditions involving SD.