Visual Estimation of Train-of-Four 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 neuromuscular block at the orbicularis oculi (OO) is shorter than at the AP. The aim of this study was to assess whether TOF at the OO can predict, 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 induced with propofol, 2-3 mg/kg, intravenously (IV), and fentanyl, 2-3 micrograms/kg IV, and maintained with a propofol infusion. Ulnar and facial nerves were stimulated simultaneously with TOF every 20 s. PTC at the AP was repeated every 5 min. The number of twitches after PTC was estimated by feeling the responses at the thumb. TOF responses at the OO were monitored visually. TOF responses at the AP were recorded using a force transducer. Patients were assigned randomly to receive either atracurium, 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 reappearance of the first response of TOF at the OO (T1OO), and to the reappearance 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, PTC1 recovered earlier than T1OO (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)