The Effects of Hypercarbia and Hypocarbia on Pancuronium and Vecuronium Neuromuscular Blockades in Anesthetized Humans

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Abstract
To determine the effects of hypercarbia and hypocarbia on a pancuronium or vecuronium neuromuscular blockade, 54 patients were anesthetized with halothane and 60% N2O in O2. In 30 patients, end-tidal PCO2 [CO2 partial pressure] was maintained at either 25 mm Hg (3.5 kPa [kiloPascal] n = 10), 41 mm Hg (5.5 kPa, n = 10) or 56 mm Hg (7.5 kPa, n = 10). Five patients in each group then were given pancuronium or vecuronium 0.022 mg/kg i.v. Neither maximal depressions of twitch tension nor recovery indexes (time for spontaneous recovery of twitch tension from 25 to 75% of control) were altered by hypercarbia or hypocarbia. The remaining 24 patients were divided into 3 equal groups. Either pancuronium (n = 8) or vercuronium (n = 8) was administered i.v. as continuous infusion at a rate sufficient to produce a 50% depression of twitch tension. In the remaining 8 patients, no muscle relaxant was given. After twitch tension was stable, half of the patients in each group had hypercarbia induced, which depressed twitch tension in all 3 groups. The patients who received vecuronium had a significantly larger decrease in twitch tension than those who received pancuronium or no muscle relaxant. In the remaining patients, hypocarbia produced a significant increase in twitch tension. There was no difference in the magnitude of the increases in twitch tension among the 3 groups. Apparently, pre-muscle relaxant administration-induced hypercarbia or hypocarbia has no effect on a subsequent neuromuscular blockade from pancuronium or vecuronium. Hypercarbia decreases and hypocarbia increases twitch tension when no muscle relaxant is given and during a partial pancuronium or veruconium neuromuscular blockade. Vecuronium was affected by hypercarbia more than the other 2 groups. When larger doses of vecuronium are given, hypercarbia may increase the danger of residual neuromuscular blockade.