Clinical Evaluation of the Neruomuscular Blocking Effect of Isoflurane

Lee, Sung Kyun; Kim, Sung Nyeun; Park, Cheol Joo; Kwon, Ou Kyoung; Park, Chong Min; Shim, Jae Young

Abstract

Isoflurane, which has only recently been introduced into clinical practice, is a nonflammable halogenated ether used as an inhalation anesthetic. It has pharmacological, physical, and clinical properties similar to those of halothane and enflurane: however, it differs from botn in several important aspecs. The potent neuromuscular blocking action of sioflurane in desirable, because it reduces the requirement for muscle relaxants and allows lower doses of anesthesis. To quantitatively clarify the neuromuscular blocking effect of isoflurane, neuromuscular function was monitored by "Train of Four" stimulus with and without administration of muscle relaxants under halothane and isoflurane anesthesis, respectively, in 60 patients. The patients were divided into 4 groups(halothane anesthesia without muscle relaxants, halothane anesthesis with muscle relaxants, isoflurane anesthesia without muscle relaxants and isoflurane anesthesia with muscle relaxants). Twich responses of thenar muscle were monitored and analysed for the value of maximaum twich depression by halothane and isoflurane anesthesia, respectively, and the onset time, degree of maximal neuromuscular blockade, duration of action and recovery index of pnscuronium bromide under halothane and isoflurane anesthesia, respectively. The results were as follows: 1) Isoflurane exhibited a neuromuscular blocking effect 2,3 times more potent than halothane. 2) Neuromuscular depression by halothane and isoflurane was not accompanied by "fade". 3) The recovery time from nuromuscular blockade by succinylcholine in isoflurane anesthesia was increased significantly compared with halothane anesthesia. 4) The duration of action and the recovery index were increased significantly in isoflurane anesthesia compared with halothane anesthesia.