Cerebrovascular response to PaCOCO2 during halothane anesthesia in man

Abstract

Twenty-four measurements of cerebral blood flow (CBF) were made with Kr⁸⁵ in 13 normal unpremedicated male subjects during halothane anesthesia. Mean end-tidal halothane concentration was 0.98%. Ve was maintained constant in each subject at about 12 liters/min and inhaled co₂ concentration was varied so that PaCO_CO2 ranged between 19–56 mm Hg. Mean cerebral perfusion pressure varied from 41.0 to 76.4 mm Hg and tended to be lower at PaCO_CO2 levels >47 mm Hg. CBF varied linearly with PaCO_CO2 under the conditions of this study. The response of the cerebral circulation to change in PaCO_CO2 during halothane anesthesia is compared with changes observed by others in awake man and in anesthetized animals. The shape of the PaCO_CO2 response curve was observed to be altered by the vasodilatation which occurred during halothane anesthesia. The Kr⁸⁵ method of calculating CBF is superior to the nitrous oxide technique because of krypton's lower blood solubility and more rapid equilibration. cerebral blood flow; general anesthesia; carbon dioxide Submitted on December 23, 1963