Concern has been expressed over the use of the halogenated anaesthetics halothane (CF3CClBrH), enflurane (CF2HOCF2CFClH) and isoflurane (CF2HOCHClCF3) because of their potential for stratospheric ozone destruction. Halogenated species also contribute to global warming. The significance of the anaesthetics in stratospheric ozone loss or in 'greenhouse' heating depends on their atmospheric lifetimes. Because reaction with hydroxyl (OH) radicals is likely to be the main homogeneous sink for these species in the troposphere, we have measured absolute rates of reaction with OH. Comparison with a one-dimensional model indicates that the lifetimes of halothane, enflurane and isoflurane with respect to this reaction are 2, 6 and 5 years, respectively. Thus the small production of the anaesthetics is not offset by anomalously long atmospheric lifetimes to give a large atmospheric burden of the compounds. The anaesthetics will contribute at most a fraction of approximately 5 x 10(-4) to the total atmospheric content of chlorine-containing species.

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We describe a patient who had a cardiac arrest during anaesthesia, in whom regional cerebral oxygen saturation was being measured by near infrared spectroscopy and the auditory evoked responses (AER) were being recorded. Both of these monitors provided useful information on cerebral oxygenation during cardiac arrest. Changes in the AER as the result of either reduced circulation or hypothermia are similar, and should these two situations occur simultaneously there could be difficulty in the interpretation of the AER.

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The instantaneous thermal energy balance and rates of thermal energy transfer during hypothermic cardiopulmonary bypass were measured for a group of patients receiving continuous flow and compared with a group receiving pulsatile flow. Cooling was more rapid and the rate of thermal energy delivery during rewarming significantly greater in the pulsatile flow group despite similar rewarming times. The final thermal energy balance at the end of cardiopulmonary bypass was larger and the period of postoperative hypothermia shorter in those receiving pulsatile flow. The greater rate of thermal energy transfer may explain the reduced afterdrop.