Effect of intravenous injection of different doses of lidocaine on cough during the recovery period after bronchoscopy under general anesthesia

Objective To evaluate the effect of intravenous injection of different doses of lidocaine on cough during the recovery period after bronchoscopy under general anesthesia, aiming to determine the optimal lidocaine dose. Methods Using prospective, single-center, randomized controlled clinical trial methods, a total of 135 patients who underwent bronchoscopy in Shunde Hospital of Southern Medical University from September 2023 to June 2024 were selected, and they were randomly divided into group C (normal saline), group L1.0 (1.0 mg/kg lidocaine), and group L1.5 (1.5 mg/kg lidocaine), with 45 cases in each group. All patients received general anesthesia with laryngeal mask. After induction, lidocaine or saline was administered intravenously. The incidence and severity of cough within 30 minutes after removal of the laryngeal mask were recorded and analyzed, along with adverse events. Cough severity was categorized as mild (single episode), moderate (multiple episodes lasting over 5 s but not continuous), and severe (continuous coughing lasting over 5 s). Results There was a statistically significant difference in the incidence of cough during the recovery period after bronchoscopy among the three groups: 42.2% in group C, 22.2% in group L1.0, and 8.9% in group L1.5 (χ2=13.72, P＜0.01), and after Bonferroni correction, that in group L1.5 was significantly lower than that in group C (χ2=13.14, P＜0.01). The incidence of severe cough was 17.8%, 4.4% and 2.3% respectively, and the difference among the three groups was statistically significant (χ2=8.51, P＜0.05). Compared with group C, the incidence of postoperative nausea, vomiting and sore throat significantly reduced in group L1.0 and group L1.5 (P＜0.017). Conclusion Intravenous injection of 1.5 mg/kg lidocaine can effectively decrease the incidence of cough during the recovery period after bronchoscopy under general anesthesia, and also can significantly reduce the occurrences of nausea, vomiting and sore throat.