Anaesthetic interaction between thiopentone and ketamine.

The anaesthetic effect of thiopentone, ketamine and their combinations were studied in 150 patients of ASA Grades I and II. The ability to open eyes on command and purposeful motor response to noxious pressure on the trapezius muscle were used as endpoints of anaesthesia. Dose-response curves for thiopentone, ketamine and their combinations were determined with a probit procedure and compared with isobolographic analysis. The interaction between thiopentone and ketamine was found to be additive for both endpoints of anaesthesia.