Xenon is a more potent anesthetic than nitrous oxide, and give more profound analgesia. This investigation was performed to assess the potential of xenon for becoming an anesthetic inspite of its high manufacturing cost. Seven ASA I-II patients undergoing cholecystectomy (n = 4), hernia repair (n = 2), or mammoplasty (n = 1) were studied. Denitrogenation by 15-20 min of oxygen breathing under propofol anesthesia was followed by fentanyl-supplemented xenon anesthesia administered via an automatic minimal flow system which held the oxygen concentration at 30%. Xenon anesthesia lasted 76-228 min and 8-14 l of xenon (ATPD) was used, of which 5.6-8.1 l was expended during the first 15 min. Anesthesia appeared to be satisfactory, and the patients woke up rapidly after xenon was discontinued. The automatic system made minimal flow xenon anesthesia easy to administer, but nitrogen accumulation is still a problem. Assuming a xenon price of 10 US$ per litre, the average cost for xenon was about 65 US$ for the first 15 min and then about 25 US$ for each subsequent hour of anesthesia.

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Anaesthesia systems that minimize the use of volatile anaesthetics to reduce cost and pollution are of interest. Closed circuit anaesthesia is the ideal solution, but requires continuous adjustment of fresh gas flow and composition and thus is demanding in routine practice. We describe an alternative system, the Reflector system, which is open in regard to oxygen, nitrogen and N2O, and semiclosed in regard to volatile anaesthetics. The Reflector system is a circle system with a carbon dioxide absorber and an automatic vapour delivery device placed in the inspiratory limb of the circle. A zeolite filter, the Reflector, is placed between the ventilator and the circle. The Reflector functions as a molecular sieve, preventing the volatile anaesthetic from leaving the circle. Isoflurane consumption using the Reflector system in bench tests and an animal study was compared with that of an open system. In bench tests consumption was reduced by 79% and 82%, at a respiratory frequency of 10 and 20 min-1, respectively. The corresponding mean figures from the animal experiment were 65% and 77%.

:Methyl vinyl ketone (7.01 g, IOOmmoI), aldehyde 5 (lOOmmol), and DABCO (1.68 g, 15 mrnol) were dissolved in anhydrous THF (25 mL) and left at room temperature. After 7 days the solution was diluted with diethyl ether, washed with dilute hydrochloric acid and aqueous NaHCO,, and dried (MgSO,). The crude product was purified by chromatography on silica gel (dierhyl ether-light petroleum) or distilled in a Kugelrohr apparatus. 8 : The coupling product 6 (iOmrnol), DABCO (3.37g, 30mmol) and pdimethylaminopyridine (120 mg, 1 mrnol) were dissolved in anhydrous CH2C12 (20 mL) and the solution cooled to 0°C. Methanesulfonyl chloride (1.37 g, 12 mmol) in anhydrous CHZC12 (10 mL) was added dropwise and the reaction mixture stirred for 24 h at room temperature. The mixture was worked up by dilution with CH2CIZ, washing with water (3 x), drying (MgSO,), and removal of the solvent. The crude mixture of stereoisomers was purified on silica gel/diethyl ether-light petroleum and-when possible-separated (cf. Table I).