ANTAGONISM OF MODERATE DEGREES OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCK BY SMALL DOSES OF NEOSTIGMINE

We have studied the influence of a reduced dose of neostigmineon recovery from vecuroniuminduced neuromuscular block in 26adult patients, using electromyographic responses to train-of-four(TOF) stimulation. Neostigmine 10, 20 or 40 µg kg^–1was administered when the first response had recovered spontaneouslyto 5–10% or 40–50% of control. Antagonism was acceptedas adequate when the first response reached 90% of control andthe TOF ratio reached 0.7. At both degrees of spontaneous recovery,neostigmine 40 µg kg^–1 evoked the most rapid antagonism.Clinical recovery was satisfactory with no differences betweengroups. Block produced by neostigmine was not observed. Thepattern of recovery of the single response and the TOF ratiowas not altered by neostigmine in the range of doses studied.We suggest that the dose of neostigmine should not be reducedbelow 40 µ kg^–1, even when all responses of theTOF are present. ^* present address: Royal Perth Hospital, Western Australia