Anesthesia and Subarachnoid Intracranial Pressure

Abstract

Intracranial pressure (ICP) was continuously monitored by the Richmond technic of Vries and Becker in 17 patients undergoing elective craniotomy. This method entails the placement, under local anesthesia, of a hollow screw through the cranium into the subarachnoid space. The screw was connected to a Statham P23Db pressure transducer with heavy vinyl tubing and with pressures recorded on a Beckman Dynograph®. The effects of 3 anesthetic technics—halothane, enflurane, and nitrous oxide-narcotic-relaxant—on ICP during induction and maintenance were compared with preinduction control pressures. Control ICP in awake, lightly premedicated patients was 15 ± 10 torr. Mask inductions with halothane and enflurane consistently caused significant increases in ICP from preinduction levels in the absence of excitement or airway obstruction. Induction with nitrous oxide-narcotic-relaxant did not increase ICP. Decreases in ICP following barbiturate administration were noted. Addition of halothane and enflurane to the inspired mixture of patients controlled and hyperventilated with nitrous oxide and oxygen caused consistent increases in ICP. With control hyperventilation (Paco2 25 ± 5 torr), the ICP did not return toward preinduction values within 5 minutes with enflurane and halothane.