Abstract: Objective To explore the median effective concentration (EC50) of propofol to inhibit intubation reaction during endotracheal intubation with a 95% effective dose (ED95) of rocuronium. Methods Adult patients who were scheduled for thyroid operation under recurrent laryngeal nerve (RLN) monitoring were selected. They were intravenously injected in sequence with 0.03 mg/kg midazolam, 3 μg/kg fentanyl and 0.5 μg/kg remifentanil. Meanwhile, propofol was given through Dixon modified sequential plasma target‑controlled infusion (where the plasma target concentration was 3.0 mg/L of propofol in the first patient, with a concentration gradient of 0.2 mg/L). After intravenous injection of 0.3 mg/kg rocuronium, tracheal intubation and mechanical ventilation were performed. The highest mean artery pressure (MAP) and/or the highest heart rate≥120% of the baseline value within 5 min after intubation was regarded as a positive intubation response. Otherwise it was considered a negative intubation response. The intubation scores were evaluated by the Cooper method. The bispectral index (BIS) values and the occurrence of electrocardiogram burst inhibition during anesthesia induction were recorded. The adverse reactions (cough, and body movement, etc.) related to postoperative intubation were recorded. Probit analysis was used to calculate the EC50 of propofol in inhibiting the tracheal intubation reaction of nerve monitoring with an ED95 of rocuronium and its corresponding 95% confidence interval (CI). Results A total of 30 cases were included in this study. There was no electrocardiogram burst inhibition in all patients during anesthesia induction. The average intubation score of all patients was above 6, and the intubation score of patients with negative intubation response was higher than that of patients with positive intubation response (P<0.05). During intubation, two patients with positive intubation response presented cough and body movement, which were not observed in other patients. All patients were followed up within 24 h after surgery, with no reports of airway related injuries such as hoarseness, dyspnea, obvious cough, or sore throat. The EC50 of propofol in inhibiting the tracheal intubation reaction of nerve monitoring and 95%CI was 3.523 (3.310, 3.796) mg/L. Conclusions The EC50 of propofol to inhibit the intubation reaction during tracheal intubation with an ED95 of rocuronium is 3.523 mg/L, which can improve intubation conditions, and inhibit intubation reaction.
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