The Effect of Halothane and Enflurane on the Contraction of Bronchial Smooth Muscle Induced by Histamine in Rabbits / 대한마취과학회지

ABSTRACT

BACKGROUND: Inhalation anesthetics are known to be bronchodilators. However there are several reports that these effects are not consistant, and depend on the way of experiments. Some reports showed that inhalation anesthetics don't affect broncheal smooth mucle contraction. So, we tried to evaluate the effects of inhalation anesthetics on the histamine induced contraction of broncheal smooth muscles in rabbits. METHODS: Isolated broncheal rings of rabbit were suspended in a Tyrode's solution. Contractions were recorded isometrically using a transducer. Cumulative dose responses of histamine (10(-6), 10(-5) & 10(-4) Mol, histamine group) were observed and also cumulative dose responses of histamine with halothane and enflurane administration (0.5 MAC & 1 MAC) were evaluated. RESULTS: A contraction by histamine was weakened with enflurane administration, but with halothane, the contraction was slightly weakened at 0.5 MAC and no changes were observed at 1.0 MAC compared to a contraction induced by histamine. CONCLUSIONS: At 0.5 MAC of halothane, a contraction induced by histamine was slightly weakened, but at 1 MAC, no changes of contraction occurred. However enflurane weakened the contraction at 0.5 MAC and 1 MAC. It showed that in vitro studies of the direct effect of inhalation anesthetics on smooth muscle contraction are different from the results of in vivo study reports.