EFFECTS OF HALOTHANE ON MUCOCILIARY ACTIVITY IN-VIVO

The effect of halothane on mucociliary activity in the rabbit maxillar y sinus in vivo was recorded photoelectrically. Administration of halo thane (1%, 2% or 4%) into the maxillary sinus induced a temporary acce leration of mucociliary activity. The peak increase (39.1% +/- 9.1%, p < 0.05, n = 5) was seen after the 4% concentration. Long-term exposur e (60 minutes) of the maxillary sinus to halothane (2%) first induced an increase of 28.4% +/- 4.6% (p < 0.05, n = 6), lasting approximately four minutes, and followed after about 15 minutes by a decrease of mu cociliary activity. The maximum decrease during the 60-minute period w as 19.6% +/- 2.8% (p < 0.05, n = 6). Mucociliary activity returned to its baseline level approximately 25 minutes after withdrawal of haloth ane. Halothane delivered to the rabbit through a tracheal cannula at 1 .1% for 60 minutes did not impair mucociliary activity in the maxillar y sinus. On the contrary it initially stimulated mucociliary activity, 19.9% +/- 2.7% (p < 0.05, n = 5). There was also an initial increase in respiratory rate from 62 +/- 7.3 to 89 +/- 12.9 breaths per minute (p < 0.05), which was noticeable offer approximately 10 seconds and la sted 4 to 5 minutes. The dose-dependent increase in mucociliary activi ty seen after short-term exposure to halothane is probalby due to stim ulation of afferent C fibers, because halothane may be considered an a irway irritant. The reversible depressant effect seen after 15 minutes of exposure is in accordance with findings in previous studies in vit ro. The mechanism by which halothane Impairs mucociliary activity is a t present not known. However, halothane administered to the lower airw ays does not impair mucociliary activity in the maxillary sinus, indic ating that halothane affects the ciliated epithelium directly and that the state of anesthesia itself has no effect on mucociliary activity.