Spontaneous recovery from nondepolarizing neuromuscular blockade: correlation between clinical and evoked responses

The effects of nondepolarizing muscle relaxants were allowed to wear off spontaneously in 10 ASA class III and IV patients following major surgery. Neuromuscular and respiratory function were followed by clinical testing and by evoked muscle responses using a train of 4 (TOF) supramaximal stimuli. At a TOF of 70 percent (range 62 to 78%), all patients sustained eye-opening, hand-grasp, and tongue-protrusion, while 9/10 sustained head-lift. Vital capacity (VC) averaged 17 ml/kg when the TOF reached 70 percent. The increase in VC correlated with the increase in TOF (r = 0.88). There was no correlation between inspiratory force (IF) and TOF, but all patients achieved an IF equal to or greater than -22 cm H2O at 70 percent. Thus, TOF correlates well with clinical signs of neuromuscular and respiratory recovery in this group of patients and complements earlier studies in healthy anesthetized patients and nonmedicated volunteers.