-Effects of Local Anesthetics on Smooth Muscle Tissue in Rat Trachea: An In Vitro Study.

Objectives: We evaluated the muscle responses of rat trachea to LA drugs, such as lidocaine and prilocaine, in terms of airway spasms.

Materials And Methods: A total of 16 male rats were used. After ketamine anesthesia, the tracheal ring of each rat was removed and placed in the organ bath in the Krebs solution. The rat tracheal veins were randomly divided into two groups based on the LA applied at the basal tonus level: group 1 (n=8), lidocaine; group 2 (n=8), prilocaine. Second, the baths were washed. Supramaximal contraction was obtained by applying acetylcholine to the tracheal rings (n=16) at a basal tonus level. The rat tracheas with supramaximal contraction were randomly divided into two groups: group 3 (n=8), lidocaine; group 4 (n=8), prilocaine. The contraction responses of each group were recorded and statistically compared.

Results: Lidocaine constituted a significant relaxation response in the tracheal tissue in both basal tonus and supramaximal tonus levels. Moreover, it was observed that the relaxation of lidocaine was higher in the supramaximal contraction than in the basal tonus tension level. However, for prilocaine, no significant change was observed in both tonus levels.

Conclusion: This study suggests that lidocaine as a LA drug should be preferred as the first choice in patients with respiratory risk, and that its use over prilocaine should be preferred, if supported by advanced clinical studies.