Postoperative residual block in postanesthesia care unit more than two hours after the administration of a single intubating dose of atracurium*

BACKGROUND Residual neuromuscular blockade continues to be a clinical problem after surgical procedures. The purpose of this study was to determine the incidence of residual paralysis in the postanesthesia care unit (PACU) after a single intubating dose of twice of the 95% estimated dose (ED95) of a nondepolarizing muscle relaxant with an intermediate duration of action. METHODS Two hundred and sixteen patients scheduled for elective surgery under general anaesthesia requiring tracheal intubation were included in the study. They received a single intubating dose of intravenous atracurium (0.5 mg/kg) to facilitate tracheal intubation. At the end of surgery, if train of four (TOF)-ratio was ≤ 0.9, neostigmine 40 μg/kg intravenously was given. If TOF-ratio was ≥ 0.9, no neostigmine was given. Also, in awake patients with TOF > 0.9, residual neuromuscular paralysis was evaluated by using clinical tests such as head lift test and tongue depressor test. RESULTS TOF was less than 0.9 in 48 (22.2%) patients while after 120 minutes, no patients had TOF less than 0.9. Of 33 patients whose operation lasted less than 120 minutes, 4 patients had TOF less than 0.9 at the end of surgery. There was no case of hypoventilation or hypoxia at PACU. The incidence of negative value in clinical tests was high. CONCLUSIONS Our study gave the impression that more than two hours between the administration of a single intubating dose of an intermediate-acting nondepolarizing muscle relaxant (atracurium) and arrival to the PACU can probably guarantee the lack of a residual paralysis.