Postoperative human reaction time and hypocarbia during anaesthesia

Abstract

To study the effect of hypocarbia during anaesthesia on postoperative performance of a reaction time test, thirty-seven selected surgical patients were anaesthetized in a manner which does not alter cerebral blood flow at normal arterial Pco2 levels. Patients were hyperventilated and variable amounts of carbon dioxide (0-2 per cent) were added to the inspired mixture to obtain a steady Paco2. A range of Paco2 of 12 to 38 mm Hg was obtained in the thirty-seven patients. In twenty patients whose Paco2 was below 24 mm Hg throughout the procedure there was postoperative prolongation of reaction time which lasted 3 to 6 days. Seventeen patients, whose Paco2 was greater than 24 mm Hg did not demonstrate this prolongation. There were no significant differences in age, sex, duration and type of procedure, anaesthetic dose, and levels of oxygenation in the two groups which could account for the observed results. © 1968 John Sherratt and Son Ltd.