[Minimal-flow xenon and semiclosed circuit anesthesia for computed tomographic measurement of local cerebral blood flow (LCBF)].

For the purpose of decreasing the volume of expensive xenon, anesthesia with minimal-flow xenon and semiclosed circuit were induced for computed tomographic LCBF measurement. Eighteen patients with ischemic cerebral disease were studied. Anesthesia was induced with minimum dose of thiopental, diazepam and fentanyl. Muscle relaxation was obtained by means of pancuronium bromide. Patients were intubated and ventilated mechanically with flows of 6 l/min. O2 for 20 to 30 minutes to eliminate nitrogen from the system. O2 concentrations in semiclosed circuit were monitored throughout the procedures using galvanic battery. Endtidal CO2 tension was also measured for maintaining normocarbia. Blood gas analyses were carried out before xenon inhalation, during xenon inhalation and immediately before stopping inhalation of xenon-oxygen mixture. Xenon inhalation programs were subdivided into three groups, each of them consisted of 6 patients. The formula for calculating fresh gas flow for low flow semiclosed circuit was introduced according to Shimoji's which was based on the original formula of Foldes. O2 concentration in circuit was predicted to be 25%. Mean xenon uptake for initial 20 minutes was predicted to be 125 ml/min. or 360 ml/min. (Formula: see text) (CRO2: O2% in semiclosed circuit. FO2: fresh O2 flow ml/min. FXe: fresh xenon flow ml/min. VO2: oxygen consumption ml/min. VXe: mean xenon uptake ml/min.) The first group started xenon inhalation during pure xenon inflow into semiclosed circuit for two minutes and followed by about 68% xenon in O2 inhalation for 23 minutes. FXe and VXe were fixed at 700 ml/min and 360 ml/min respectively.(ABSTRACT TRUNCATED AT 250 WORDS)