BACKGROUND AND OBJECTIVES: The priming principle consists of administering a low neuromuscular blocker dose, minutes before the total dose for tracheal intubation, to shorten non-depolarizing blockers onset. There is, however, the risk for muscle fade and bronchoaspiration. Laryngeal muscles are of especial interest for tracheal intubation maneuvers and airway protection. Since their direct monitoring imposes technical difficulties, it has been reported that orbicularis oculi correlates with laryngeal muscles in terms of sensitivity to neuromuscular blocks. This study aimed at evaluating the presence of orbicularis oculi muscle fade after priming atracurium dose and at comparing clinical tracheal intubation conditions after two priming dose intervals. METHODS: Participated in this study 35 adult patients, physical status ASA I or II, without risk factors for bronchoaspiration and submitted to elective surgeries. General anesthesia was induced with alfentanil and propofol and patients were manually ventilated under mask. Surface electrodes were then positioned on the temporal branch of the facial nerve, and the acceleration transducer was placed on the orbicularis oculi. Priming atracurium dose (0.02 mg.kg-1) was administered and T4/T1 ratio was evaluated every minute during 5 minutes in 20 cases (G1) and during 7 minutes in 13 cases (G2). After this interval, complementary atracurium dose (0.5 mg.kg-1) was administered and tracheal intubation was performed one minute later. Fade was defined as T4/T1 ratio below 0.9. RESULTS: There has been no fade in any patient during the monitoring interval. In 80% and 69% of G1 or G2 patients, respectively, tracheal intubation was classified as clinically acceptable (p > 0.05). CONCLUSIONS: Priming atracurium dose (0.02 mg.kg-1) does not determine orbicularis oculi fade and there is no difference between 5 or 7 minutes priming intervals.
MONITORING; NEUROMUSCULAR BLOCKERS; NEUROMUSCULAR BLOCKERS; TRACHEAL INTUBATION
