Sequential changes in the fade of tetanic tension after the administration of tubocurarine in anaesthetized man.

Tetanic and single twitch contractions of the adductor pollicis muscle in anaesthetized man were measured continuously following the i.v. injection of tubocurarine 0.2 mg/kg. Tetanic contractions were depressed earlier by tubocurarine and to a greater extent compared with the single twitch. Recovery was also slower for the tetanic contractions. The fade of tetanic tension was also measured throughout the blockade produced by tubocurarine. Fade was expressed in terms of the tetanic tension ratio: the ratio of the magnitude of the muscle tension at the end of 1 s of tetanic contraction compared with its peak height at the beginning of that contraction. Tetanic tension was well maintained during the onset of the neuromuscular block but was less well maintained during the recovery phase. It is suggested that the assessment of tetanic tension fade shoudl be carried out throughout the various stages of curarization.