BACKGROUND Acute normovolaemic haemodilution (ANH) is an efficacious blood conservation strategy aiming at avoiding allogeneic blood transfusion. ANH was shown to increase the potency of vecuronium, atracurium, and rocuronium. The aim of our study was to investigate whether cisatracurium potency is altered with ANH. METHODS Using the Relaxometer mechanomyograph, we compared cisatracurium dose-response relationship and time course of action in
60 patients randomly allocated to the ANH or control groups. Patients in each group were randomly allocated to receive one of three cisatracurium doses (30, 40, 50 microg kg(-1)) followed by a second supplemental dose to reach a total of 100 microg kg(-1). RESULTS ANH did not result in a significant shift in cisatracurium log dose-probit dose-response curve. There was no significant difference in mean (95% confidence intervals) ED(50), ED(90), and ED(95) (effective doses required for 50, 90, and 95% first twitch depression) between the ANH group [29. 5 (27-32), 50. 4 (47. 4-53. 4), 58. 7 (55. 3-62) microg kg(-1)] and the control group [28. 2 (25. 3-31), 47. 6 (44. 9-50. 3), 55. 3 (52. 5-58. 1) microg kg(-1)], whereas there was no difference in mean (SD) Dur(25) and Dur(0. 8) (time until 25% first twitch and 0. 8 train-of-four ratio recoveries) between the ANH group [40. 8 (5. 9), 64. 7 (8. 4) min] and the control group [42. 2 (7. 6), 66. 5 (10. 7) min]. CONCLUSIONS Our results demonstrated that unlike other previously reported neuromuscular blocking drugs, ANH did not alter cisatracurium potency. Thus, cisatracurium would be the neuromuscular blocking drug of choice in patients who undergo surgery with ANH, as no dose adjustments are required.
