[Preventive effect of atropine premedication on vagal reflex in patients undergoing suspension laryngoscopy during anesthesia induction].

To evaluate the preventive effect of atropine premedication during anesthesia induction on vagal reflex in patients undergoing suspension laryngoscopy. A total of 342 patients (202 males and 140 females) scheduled for suspension laryngoscopy under general anesthesia in Beijing Tongren Hospital from October 2021 to March 2022 were prospectively enrolled, with a mean age of (48.1±11.9) years. The patients were randomly divided into two groups using the random number table method: the treatment group (=171) and the control group (=171). Patients in the treatment group were administrated with 0.5 mg atropine intravenously guttae (ivgtt) while patients in the control group were given equivalent volume of normal saline. For all patients, if heart rate (HR)<50 beats/min happened during the insertion of the suspension laryngoscope, the operation should be stopped and the laryngoscope should be removed. Patients without HR recovery after the removal of the laryngoscope should be given 0.5 mg atropine, and the operation should be continued after the HR recovered. The primary outcome was the incidence of HR fluctuation over 20% (ΔHR>20%) before and immediately after suspension laryngoscope fixation, and the secondary outcomes included HR, mean arterial pressure (MAP) of the two groups recorded before and after anesthesia induction, before and immediately after suspension laryngoscope fixation, and the incidences of sinus bradycardia, laryngoscope removal and atropine treatment during operation. The incidences of ΔHR>20% and bradycardia immediately after the suspension laryngoscope fixation were 14.6% (25/171) and 12.9% (22/171) in the treatment group, which were significantly lower than those in the control group [28.1% (48/171) and 29.8% (51/171)] (both <0.05). The HR immediately after the suspension laryngoscope fixation in the treatment group [(66.4±13.5) beats/min] and in the control group [(60.8±15.7) beats/min] was significantly lower than those before the suspension laryngoscope fixation [(74.7±11.1) beats/min and (67.6±12.8) beats/min, respectively] (both <0.05). There were no significant differences in MAP between the two groups at each time point (all >0.05). The incidence of laryngoscope removal once plus 0.5 mg atropine administration, laryngoscope removal twice plus 0.5 mg atropine administration and laryngoscope removal twice plus 1.0 mg atropine administration was 9.9% (17/171), 1.8% (3/171) and 0 (0) in the treatment group, respectively, which was significantly lower than those in the control group [24.0% (41/171), 5.8% (10/171) and 2.3% (4/171), respectively] (all <0.05). Atropine premedication during anesthesia induction can effectively reduce the occurrence of vagal reflex in patients undergoing suspension laryngoscopy.