COMPARISON OF THE NEUROMUSCULAR BLOCK INDUCED BY MIVACURIUM, SUXAMETHONIUM OR ATRACURIUM DURING NITROUS OXIDE-FENTANYL ANAESTHESIA!

Mivacurium chloride is a new non-depolarizing neuromuscular blocking drug, structurally related to atracurium [1]. It has a duration of action which appears shorter than that of other currently available non-depolarizing neuromuscular block-ing agents [1], but longer than that of suxa-methonium [2]. It is eliminated via metabolism by plasma pseudocholinesterase [1, 3]. There have been no published comparisons of mivacurium with both suxamethonium and atracurium under the same experimental conditions. Our aim was to define the neuromuscular blocking actions and cardiovascular effects of mivacurium and compare them with those of suxamethonium and atra-curium. PATIENTS AND METHODS With approval from our Committee on Human Research and written, informed patient consent, we studied 41 patients (ASA physical status I or II) undergoing various surgical procedures. No patient was taking medications or suffered from any disease known to affect neuromuscular func-tion. Following premedication with midazolam 0.02-0.08 mg kg"1 i.v., anaesthesia was induced with fentanyl 5-10 \ig kg"1, followed by thio-pentone 2-6 mg kg"1 i.v. Tracheal intubation wa