Saving sevoflurane and hastening emergence from anaesthesia using an anaesthetic-conserving device

Abstract

This study compared an anaesthetic-conserving device (AnaConDa) and a conventional vaporizer in terms of sevoflurane consumption and emergence from anaesthesia using a total gas flow of 4 l min(-1), with a rebreathing circuit. Twenty-four patients for gastrectomy, aged 30-70 years, were divided into AnaConDa and control groups. Anaesthesia was induced with midazolam, propofol, fentanyl and vecuronium. The total gas flow was fixed at 4 l min(-1) (nitrous oxide 2 l min(-1) and oxygen 2 l min(-1)). Sevoflurane administration was started at 0.5% (vaporizer setting) in the control group and 25 ml h(-1) in the AnaConDa group, then the end-tidal sevoflurane concentration was kept between 0.3 and 0.5% in both groups. Analgesia was obtained with intermittent epidural administration of mepivacaine. The time to first detection of end-tidal sevoflurane, sevoflurane consumption and emergence time were compared between the two groups. The AnaConDa group showed a significantly longer time to first detection of end-tidal sevoflurane (211 +/- 75 vs. 40 +/- 18 s), smaller sevoflurane consumption (12 +/- 3 vs. 42 +/- 9 ml), and shorter emergence time (12 +/- 2 vs. 16 +/- 1 min) than the control group. The AnaConDa could decrease sevoflurane consumption and hasten emergence from anaesthesia, but increasing sevoflurane concentration with AnaConDa at the start of anaesthesia might take longer than that with a conventional vaporizer.