The influence of propofol, remifentanil and lidocaine on the tone of human bronchial smooth muscle.

Bronchoscopy is generally a safe procedure, but the induction of anaesthesia can induce bronchospasm. Consequently we investigated the influence of propofol, remifentanil and lidocaine on the tone of the human bronchial smooth muscle. Materials and methods: The influence of propofol, remifentanil and lidocaine on the contractile response of human bronchial smooth muscle to electrical field stimulation (EFS) has been evaluated. The role of capsaicin-sensitive sensory nerves and of inducible nitric oxide synthase has also been assessed. Furthermore, the interaction between these three dugs has been measured by Bliss Independence (BI) theory. Statistical significance (P < 0.05) was assessed by Student's t test or ANOVA. Results: Propofol (1.3 μg ml-1) and lidocaine (1 mg ml-1) reduced the baseline tone of bronchial rings (-14.45 ± 4.53% and -33.40 ± 1.07%, respectively, P < 0.05), whereas remifentanil had not such effect. Aminoguanidine prevented the relaxant effect of propofol. Propofol did not alter the bronchial contractile response to EFS following 30 min of treatment, whereas remifentanil enhanced the bronchial tension (133.83 ± 9.38%, control 101.93 ± 6.82%, P < 0.05 P < 0.05) and lidocaine completely abolished the contractility at 1 mg ml-1 (P < 0.05). The desensitization of capsaicin-sensitive sensory nerves normalized the hyperresponsiveness induced by remifentanil (-26.77 ± 1.68%, P < 0.05). Significant BI antagonism (P < 0.001) was detected for propofol and lidocaine on the bronchial hyperresponsiveness induced by remifentanil. Conclusion: Propofol and remifentanil may be used safely for bronchoscopy, although remifentanil should be associated with propofol or lidocaine to prevent the potential opioid-mediated bronchospasm.