Effect of hypocarbia and hypercarbia on the antagonism of pancuronium-induced neuromuscular blockade with neostigmine in man

Abstract

Summary: The effects of variations in carbon dioxide concentration on the antagonism of pancuronium-induced neuromuscular block by neostigmine were studied in 21 patients, normocarbia (PE'CO2 5.4%, PaCO2 4.93 kPa, n = 7), hypocarbia (PE'CO2: 3 6%, PaCOl 3.30 kPa, n= 7) and hypcrcarbia (PE'CO27.5%, PaCO2 713kPa, n = 7). Mechanical and electromyographic responses to ulnar nerve stimulation (0.1 Hz and 2 Hz) were recorded A 90% block during nitrous oxide in oxygen anaesthesia was maintained by incremental single injections of pancuronium and reversed with neostigmine 0.035 mgkg-1 with atropine 0.0175mgkg-1. The recovery of twitch tension up to 50% was similar in all groups but thereafter slower in the hypercarbia group. The recovery times from 25% to 75% twitch tension correlated with PaCO2 (r = 0.55, P<0.05). A residual block of about 10% was seen in hypercarbic patients. However, the recovery of e.m.g. amplitude and train-of-four ratios was similar in all groups. Thus, the unpaired recovery of twitch tension seems to be the result of depressed contractility rather than failure of neuromuscular transmission © 1982 Macmillan Publishers Ltd.