CHANGES IN MUCOCILIARY ACTIVITY MAY BE USED TO INVESTIGATE THE AIRWAY-IRRITATING POTENCY OF VOLATILE ANESTHETICS

We have examined the short-term effects of th ree volatile anaesthetic s, halothane, isoflurane and desflurane, on mucociliary activity in th e rabbit maxillary sinus in vivo. Mucociliary activity was recorded ph otoelectrically and the signal processed by fast Fourier transformatio n. Administration of 1.0 MAC of halothane, isoflurane or desflurane ca used a temporary increase in mucociliary activity, with mean peak resp onses of 47.8 (SEM 13.0)%, 44.0 (9.6)% and 45.1 (23.7)% (n=6), respect ively. The response to all three compounds was biphasic; an initial pe ak was observed within 2 min and a second peak at 3-8 min. The second response was not significant for halothane. In contrast, desflurane pr oduced a significant second peak while the first was small and failed to reach significance. Halothane displayed an initial peak within 2 mi n which was blocked by atropine but not by the neurokinin 1 (NK1) rece ptor antagonist CP-99. The second peak at 3-5 min was less pronounced for halothane than for isoflurane or desflurane. The second peak was n ot affected by atropine pretreatment, but was blocked by pretreatment with CP-99. A combination of atropine and CP-99 pretreatment abolished the mucociliary response to halothane. Atropine pretreatment did not affect, whereas CP-99 significantly reduced, the response to desfluran e. We conclude that the NK1-mediated response was most pronounced for desflurane which is considered the most airway irritating compound of the three. It is likely that the size of the NK1-mediated response ref lects the airway-irritating properties of the volatile anaesthetic use d.