Isobutene formation during halothane anaesthesia in man.

The concentrations of volatile hydrocarbons were studied in breath samples from patients before and after anaesthesia. In patients to whom halothane was administered, there was a significant increase in the concentration of isobutene (from 0.43 +/- 0.09 to 4.66 +/- 2.22 nmol litre-1). There was no change in the concentration of isobutene in six patients anaesthetized with ketamine and diazepam. The concentrations of ethane and pentane were not altered significantly in either group.