Central circulation during halothane-diethyl-ether azeotrope and isoflurane anaesthesia in the pig

The fatal anaesthetic ratio (FAR) has been determined for halothane-diethyl-ether (HE) in pigs, and the central circulation during hypovolaemia has been investigated using a well-documented agent such as isoflurane as a standard. The fatal anaesthetic ratio for HE in pigs was (3.21/1.03) = 3.12. This is high compared to the FAR for halothane of 1.7. The central circulation was investigated in 12 pigs which were randomly allocated to either HE or isoflurance anaesthesia, respectively. Baseline values were recorded when they were stable at 1.3 MAC of the volatile anaesthetic used. The pigs were bled 30% of their blood volume, and measurements were made at 5 and 30 min. There was one significant difference between these groups in central circulation: the blood pressure was higher at baseline measurement in the HE group. At 5 min and 30 min, there were no significant differences between these groups. There was a general depression of central circulation without any sign of decreased contractility. HE anaesthesia is well tolerated during hypovolaemia in pigs.