CONTROLLED ANAESTHESIA: A CLINICAL EVALUATION OF AN APPROACH USING PATIENT CHARACTERISTICS IDENTIFIED DURING UPTAKE

The performance of a system to control the alveolar concentrationof halothane in patients undergoing halothane and nitrous oxideor halothane anaesthesia with controlled ventilation has beenevaluated. The method involved the identification and quantificationof the uptake characteristics of patients from their early responseto the anaesthetic and implements the vaporizer control necessaryto achieve and maintain a desired alveolar halothane concentration.Initial targets are based on the concept of MAC, but modificationsto the desired alveolar concentration may be effected readilyby the anaesthetist at any time during the procedure if evaluationof the normal clinical signs indicates inappropriate depth ofanaesthesia. The results obtained during anaesthesia for routinesurgery in 80 patients demonstrated that the system was accurate,stable, robust and able to adapt for variability between patientsin the uptake of halothane.