VISUAL ESTIMATION OF TRAIN-OF-4 RESPONSES AT THE ORBICULARIS OCULI AND POSTTETANIC COUNT AT THE ADDUCTOR POLLICIS DURING INTENSE NEUROMUSCULAR BLOCK

Posttetanic count (PTC) predicts the time to return of train-of-four ( TOF) responses at the adductor pollicis (AP) muscle. The duration of n euromuscular block at the orbicularis oculi (OO) is shorter than at th e AP. The aim of this study was to assess whether TOF at the OO can pr edict, as accurately as PTC does, the time to return of TOF at the AP. Twenty patients, ASA grade I or II, were studied. Anesthesia was indu ced with propofol, 2-3 mug/kg, intravenously (IV), and fentanyl, 2-3 m ug/kg IV, and maintained with a propofol infusion. Ulnar and facial ne rves were stimulated simultaneously with TOF every 20 s. PTC at the AP was repeated every 5 min. The number of twitches after PTC was estima ted by feeling the responses at the thumb. TOF responses at the OO wer e monitored visually. TOF responses at the AP were recorded using a fo rce transducer. Patients were assigned randomly to receive either atra curium, 0.5 mg/kg (n = 10), or pancuronium, 0.1 mg/kg (n = 10). Times from injection to the first response to PTC (PTC1), to the reappearanc e of the first response of TOF at the OO (T1OO), and to the reappearan ce of the first response of TOF at the AP (T1AP) were recorded. After pancuronium and atracurium, PTC1 and T1OO recovered before T1AP (P < 0 .001). In all patients, PTC, recovered earlier than T1OO (P < 0.001). T1OO occurred 11 min and 27 min before T1AP after atracurium and pancu ronium, respectively. Because recovery of T1OO occurs earlier than T1A P in all patients, monitoring of the OO can be useful to predict the t ime of reappearance of TOF at the AP.