RESUMEN
PURPOSE: The study aimed to determine the efficacy of lidocaine at different low doses to reduce fentanyl-induced cough (FIC). METHODS: Three hundred twenty patients aged from 18 to 60 years with ASA I and II scheduled for general anesthesia were randomly assigned to 4 groups to obtain peripheral intravenous 0.9%NaCl (Group I), lidocaine 0.25 mg/kg (Group II), 0.5 mg/kg (Group III) or 1.0 mg/kg (Group IV) 2 min before 3 µg/kg of fentanyl intravenously in a prospective randomized controlled fashion. The primary result was incidence of cough among comparison groups. The secondary results included severity of cough, hemodynamic response and risk factors of FIC. RESULTS: Thirty-two, 15, 13 and 11 patients (40, 18.8, 16.3 and 13.8%) presented incidence of cough in Groups I, II, III and IV, respectively (P < 0.05 Group I vs. II, III and IV). No significant difference was observed in the incidence and severity of cough among the lidocaine groups (P > 0.05). Multivariate analysis showed that age ≤ 40 years, nonsmoking and patients not receiving the prior lidocaine injection were risk factors of FIC (P = 0.007, 0.013 and 0.001, respectively). CONCLUSION: The study implied intravenous lidocaine 0.25 mg/kg for 2 min before fentanyl injection was the most effective dose to suppress FIC and could be applied in daily practice. Patients aged less than 40 years and nonsmoking were risk factors of FIC, regardless of sex and underlying disease.