Vagally mediated sympathoexcitation and central depression by desflurane in rabbits

The effects of desflurane on renal sympathetic nerve activity (RSNA) were s tudied in intact or vagotomized anaesthetized rabbits with initial concentr ations of 4.5-18%, subsequently equilibrated to end-tidal concentrations fr om 3%, 6%, 9% and 12% each for 20 min allowing sympathetic activity to stab ilize. In intact animals, immediate transient increases in mean sympathetic activity from 27% to 63% were closely related to initial concentrations fr om 4.5% to 18%. During subsequent equilibration this remained elevated by 2 5-30% up to 6%, returned to control at 9% and fell by 33% at 12%. Bilateral vagotomy abolished sympathoexcitation apart from small increases in sympat hetic activity, for example 14% at 4.5% (P<0.05). We conclude that increase s in inspired desflurane concentrations evoked rapid transient vagally medi ated reflex sympathoexcitation with a small extra-vagal contribution. Centr al depression of sympathetic activity started at 6% and was 33% below basel ine at 12%.