CLINICAL STUDIES OF INDUCTION AGENTS XXVI: THE RELATIVE POTENCIES OF THIOPENTONE, METHOHEXITONE AND PROPANIDID

Abstract

A method is described for estimating the relative potencies of intravenous anaesthetics. It is based on the time of onset of sleep after administration of various doses of the agent. Rapid transport from the periphery is achieved by injection at the height of a period of reactive hyperaemia. There are various methods of interpreting the results, but for this purpose the most reliable would seem to be the dose producing anaesthesia, as shown by the inability of the patient to count, in 90 per cent of patients within 11 seconds of the end of the injection. Studies of thiopentone, methohexitone and propanidid were carried out and gave the potency ratio for methohexitone to thiopentone as 3.3 to 1 and for thiopentone to propanidid as 1.1 to 1.