INFLUENCE OF ACUTE NORMOVOLEMIC HEMODILUTION ON THE RELATION BETWEEN THE DOSE AND RESPONSE OF ROCURONIUM BROMIDE

The influence of acute moderate haemodilution on the relation between dose and response for rocuronium was evaluated in 60 adult patients, A SA grade I, undergoing elective plastic surgery. The patients were ran domly allocated to either the control or the haemodilution group. Foll owing the induction of general anaesthesia, the status of acute modera te haemodilution in the haemodilution group was achieved by draining v enous blood, and intravenous infusion of lactated Ringer's solution, 6 % dextran or gelofusine, during which the levels of haemoatocrit and h aemoglobin dropped from 44% to 27.5% and from 148.3 to 91.3 g L-1, res pectively. Neuromuscular function was assessed mechanomyographically w ith train-of-four stimulation at the wrist every 12s and the percentag e depression of T-1 response was used as the study parameter. The rela tion between dose and response for rocuronium in the two groups was de termined by the cumulative dose-response technique. The results showed that the dose-response curve for rocuronium during acute moderate hae modilution was shifted in a parallel fashion to the left and the poten cy of rocuronium was increased. There were significant differences in ED50, ED90 and ED95 between the two groups. The ED50, ED90 and ED95 of rocuronium in the haemodilution group was decreased by 28.2%, 35.4% a nd 38.8%, respectively, compared with the control group.