THE CARDIOVASCULAR EFFECTS OF TEFLURANE IN THE CAT BY

Teflurane, a halogenated hydrocarbon anaesthetic, was compared with approximately equipotent concentrations of cyclopropane and halothane in studies made in cats. It induced spontaneous ventricular arrhythmias in a higher proportion of animals than halothane, these irregularities being abolished by the intravenous injection of pro-pranolol. Teflurane caused a profound lowering of arterial blood pressure in all the animals studied. As with halothane there was no significant increase in plasma cate-cholamine level when teflurane was inhaled. Respiratory and metabolic acidosis contributed to a lowering of plasma pH during teflurane anaesthesia. The inhalation of cyclopropane was accompanied by similar changes, whereas halothane caused some respiratory but only slight metabolic acidosis when high concentrations were given to the spontaneously breathing cat. Teflurane, 1,1,1,2, tetrafluoro-2-bromethane, is a non-inflammable and non-explosive inhalational anaesthetic, the chemical structure of which bears a close resemblance to halothane (fig. 1). The compound has a low boiling point (8°C) and since it is stored under pressure in liquefied form in metal cylinders, a vaporizer is not re-quired for its use. On this account and because the inhaled anaesthetic concentrations of the two agents are roughly comparable, teflurane has been referred to as "non-explosive cyclopropane". The new agent has a blood/gas partition coefficient of 0.6 and produces rapid induction and allows rapid recovery from anaesthesia. In an early clinical study Artusio and Van Poznak (1961) found that a 50 per cent mixture of teflurane with oxygen was suitable for in-duction of anaesthesia, and a 25 per cent mixtur