COMPARISON OF THE ONSET, SPONTANEOUS-RECOVERY AND TRAIN OF 4 FADE OF THE CLINICAL NEUROMUSCULAR BLOCK PRODUCED BY PANCURONIUM AND PIPECURONIUM

The following study was performed to delineate the possible differences in the onset, recovery and ''train of four'' (TOF) fade characteristics of pancuronium (Pan) and pipecuronium (Pip). Eighty adult American Society of Anesthesiologists (ASA) class I and II surgical patients were studied with institutional approval. After premedication, general anesthesia was induced with thiopental sodium i.v. followed by N-2/O-2 halothane and fentanyl. The lungs were ventilated. Normocarbia and normothermia were maintained. Two groups of 40 patients received pancuronium (0.1 mg/kg i.v.) or pipecuronium (0.07 mg/g i.v.). Neuromuscular block (NMB) was measured simultaneously by mechanomyography (MMG) and electromyographically (EMG) on the thumb adductor muscle. Supramaximal (TOF) stimuli were applied to the ulnar nerve every 20 seconds. The onset of neuromuscular blocking action, duration of action (to 25% recovery of twitch response), TOF fade during onset and up to 25% T-1 response recovery, hemodynamic changes following induction of anesthesia and after the muscle relaxant and subsequent oral intubation were determined. Mean values and the differences in the two treatments groups were statistically analyzed. The onset of action of the two agents were similar: 3.62+/-0.02 minutes (MMG) and 4.94+/-0.05 minutes (EMG, Pan) and 3.74+/-0.02 minutes (MMG) and 4.36+/-0.012 minutes (EMG, Pip). TOF fade ratios during the onset phase were similar. TOF fade at the 25% twitch responses recovery level was 100% with the MMG responses and (96% (Pan) and 94.8% (Pip) with the EMG responses at the 25% twitch response recovery level. Hemodynamic changes were similar after the single dose adminstration of the bolus administration of the two NMB agents. The only difference between the two treatment groups was in the degree of tachycardia in response to endotracheal intubation which was marginally more significant with Pan than with Pip (p=0.1>0.05). The clinical NMB onset of action and TOF fade characteristics of equipotent doses of Pan and Pip are identical. The duration of action of Pip was about 10% (p=<0.01) shorter than that of Pan, (The probable cause of this difference may be due to a differing influence of halothane anesthesia on the duration of NMB of otherwise equipotent NMB doses of these agents). Essentially no difference was observed in the hemodynamic data between the two treatment groups during the periods of induction of anesthesia.