Neostigmine antagonism of rocuronium block during anesthesia with sevoflurane, isoflurane or propofol

Purpose: To examine the influence of continuing administration of sevoflura ne or isoflurane during reversal of rocuronium induced neuromuscular block with neostigmine, Methods: One hundred and twenty patients, divided into three equal groups, were randomly allocated to maintenance of anesthesia with sevoflurane, isof lurane or propofol. Neuromuscular block was induced with rocuronium and mon itored using train-of-four (TOF) stimulation of the ulnar nerve and recordi ng the force of contraction of the adductor poilicis muscle. Neostigmine wa s administered when the first response in TOF had recovered to 25%. At this time the volatile agent administration was stopped or propofol dosage redu ced in half the patients in each group (n = 20 in each group). The times to attain TOF ratio of 0.8, and the number of patients attaining this end poi nt within 15 min were recorded. Results: The times (mean +/- SD) to recovery of the TOF ratio to 0.8 were 1 2.0 +/- 5.5 and 6.8 +/- 2.3 min in the sevoflurane continued and sevofluran e stopped groups, 9.0 +/- 8.3 and 5.5 +/- 3.0 min in the isoflurane continu ed and isoflurane stopped groups, and 5.2 +/- 2.8 and 4.7 +/- 1.5 min in th e propofol continued and propofol stopped groups (P < 0.5-0.1), Only 9 and 15 patients in the sevoflurane and isoflurane continued groups respectively had attained a TOF ratio of 0.8 within 15 min (P < 0.001) for sevoflurane) . Conclusions: The continued administration of sevoflurane, and to a smaller extent isoflurane, results in delay in attaining adequate antagonism of roc uronium induced neuromuscular block.