The effect of cardiac output on the onset of neuromuscular block by vecuronium.

A relationship between cardiac output and the onset time of neuromuscular blockade administered into a peripheral vein was evaluated in 41 adult patients. Anaesthesia was induced with midazolam and fentanyl and maintained with intermittent doses of fentanyl and 66% nitrous oxide in oxygen. After immobilisation of the forearm in a splint, the ulnar nerve in the other arm was stimulated supramaximally every 10 s and the adduction force of the thumb was recorded. The times from administration of vecuronium 0.08 mg.kg-1 to first and 95% depression of twitch response was 82.4 (18.0) s and 191.7 (33.5) s (mean, SD), respectively. A significant correlation between cardiac index and the onset time of blockade was observed. This study demonstrated that the rapidity of the onset of paralysis in the adductor pollicis muscle after vecuronium injection into a peripheral vein is clearly related to cardiac output.