Hypocarbia and spontaneous recovery from vecuronium neuromuscular blockade in anesthetized patients

The effect of hypocarbia on the recovery from the neuromuscular blockade produced by vecuronium was studied in 20 anesthetized patients. Vecuronium was administered until twitch tension was reduced to between 0-15% of control. Neuromuscular function was then allowed to spontaneously recover during continued normocarbia (end-tidal PCO2 5.5 kPa [41 mm Hg]) in half the patients, and in the other half of the patients hyperventilation producing hypocarbia (mean end-tidal PCO2 of 3.1 +/- 0.4 kPa SD [23 +/- 3 mm Hg] at the completion of twitch force recovery) was initiated at the beginning of spontaneous recovery from neuromuscular blockade. The mean vecuronium recovery index (time for spontaneous recovery from 25-75% of control twitch tension) was slightly but not significantly shorter in the hyperventilated patients (8.4 +/- 1.8 min SD) than in the normally ventilated patients (10.4 +/- 3.4 min SD). We conclude the vecuronium recovery index in anesthetized patients is not significantly changed by hyperventilation with hypocarbia when induced at the beginning of recovery from neuromuscular blockade.