The skeletal muscle response to edrophonium during neuromuscular blockade by tubocurarine in anaesthetized man.

Tetanic contractions of the adductor pollicis muscle in man were evaluated continuously after the administration of tubocurarine 0.2 mg/kg and during reversal by edrophonium 0.1 mg/kg. Single twitch contractions of the adductor pollicis were measured simultaneously. The response of tetanic and single twitch contractions during the reversal of tubocurarine blockade by edrophonium were compared. With the tetanic contractions edrophonium, given at recovery up to 20% of the control value, increased the peak tetanic height and restored fully sustained tetanic contractions. This reversal, however, lasted only 3-4 min. The initial peak force of the tetanus settled at a slightly greater level than the value before the administration of edrophonium. The single twitch, however, was reversed and this reversal was well maintained and showed no decline. The results indicate that tetanic and single twitch contractions of the adductor pollicis muscle in man probably represent different aspects of the responses of the neuromuscular junction to edrophonium. The recording of the single twitch alone during the reversal of neuromuscular blockade by edrophonium could lead to a false conclusion about the recovery of transmission.