Xenon expenditure and nitrogen accumulation in closed-circuit anaesthesia

The high price of xenon has prevented its use in routine, clinic anaestheti c practice. Xenon therefore has to be delivered by closed-circuit anaesthes ia. The accumulation of nitrogen is a significant problem within the closed circuit and necessitates flushing, which in turn increases gas expenditure and costs. In previous investigations, nitrogen concentrations between 12% and 16% have been reported in closed-circuit anaesthesia. In order to avoi d such nitrogen accumulation, we denitrogenised seven pigs using a non-rebr eathing system and connected the animals to a system primed with a xenon/ox ygen mixture. In comparison, seven pigs were anaesthetised with xenon using a standard low-flow anaesthetic procedure. Anaesthesia time was 2 h. Nitro gen concentrations in the closed system ranged from 0.08 to 7.04% and were not significantly different from those observed during low-flow anaesthesia . Closed-circuit anaesthesia reduced the xenon expenditure 10-fold compared with low-flow anaesthesia.