The pharmacodynamics of vecuronium in chronic renal failure patients: the impact of different priming doses.

The concept of priming was introduced to facilitate a faster onset of nondepolarizing neuromuscular blocker for endotracheal intubation. Vecuronium is still very much in use for most chronic renal failure patients posted for renal transplantation. The aim of this study was to examine the pharmacodynamics of vecuronium without and with preceding different small doses. One hundred chronic renal failure patients were assigned into four groups according to the used vecuronium priming regimen. The first control group (V(0)-group), where no priming dose was given. The other three priming groups (V(10)- , V(15)- , and V(20)-groups), where 10%, 15%, and 20% of ED(95) of vecuronium were administrated 5 min prior to the remaining intubating dose (2 × ED(95)) of vecuronium. Neuromuscular blockade was measured via acceleromyographic response of the ulnar nerve. Train-of-four (TOF) ratio was measured every minute during priming interval. Any unpleasant symptoms during precurarization were recorded. Lag time and onset time (from injection of intubating dose) were recorded. Endotracheal intubation condition was scored blindly. The duration and recovery times were also recorded. The significant higher incidence of symptoms of paresis was encountered in V(20)-group in comparison with other two priming groups. TOF ratio started to decrease significantly at the first minute in V(20)-group, at the second minute in V(15)-group, and at the third minute in V(10)-group, till the fourth minute in the priming interval. Although TOF ratio was still above 0.90 in V(10)-group, it was below 0.80 in V(20)-group. Priming groups did not show significant intergroup difference in onset time. However, duration and recovery times were significantly longer in priming groups in comparison with V(0)-group without priming. Priming the chronic renal failure patients with 10% of ED(95) vecuronium dose acquit the best pharmacodynamics with the fewest signs of muscle weakness. Larger vecuronium priming doses are unfavorable and convey no more clinical utility.