MONITORING THE ONSET OF NEUROMUSCULAR BLOCK AT THE ORBICULARIS OCULI CAN PREDICT GOOD INTUBATING CONDITIONS DURING ATRACURIUM-INDUCED NEUROMUSCULAR BLOCK

This study was designed to assess whether monitoring the orbicularis o culi (OO) can predict good tracheal intubating conditions. Fifty patie nts, ASA grade I or II were studied. Anesthesia was induced with thiop ental (5 mg/kg) and fentanyl (3 mu g/kg). The ulnar and facial nerves were simultaneously stimulated using train-of-four (TOF) stimulations every 10 s. The responses of the adductor pollicis (AP) and the OO wer e estimated visually. Patients were randomly allocated to receive eith er atracurium 0.5 mg/kg (n = 30) or 0.3 mg/kg (n = 20). In each group, endotracheal intubation was performed randomly when the OO or the AP was completely blocked. if complete block was not obtained, intubation was performed 300 s after administration of atracurium. Intubating co nditions were scored on a 1 to 4 scale. All intubations were performed by the same physician unaware of the dose and the muscular responses. After 0.5 mg/kg, both muscles were completely blocked in all patients . The average onset time (time from the injection of atracurium to the disappearance of all muscular responses after TOF) was shorter at the OO (2.35 +/- 0.12 min) than at the AP (3.59 +/- 0.15 min) (P < 0.001) (mean +/- SD). Endotracheal intubating conditions were comparable in both groups: good or excellent after 0.5 mg/kg. After 0.3 mg/kg, compl ete block was achieved only 2/20 at the OO and 12/20 at the AP. Intuba ting conditions were comparable in both groups: poor or inadequate, ex cept in the two patients with complete OO block, for whom conditions w ere good. It is concluded that OO monitoring can predict good intubati ng conditions earlier than AP monitoring when using 0.5 mg/kg but not 0.3 mg/kg atracurium.