Abstract
The effects of isoflurane versus halothane on cardiac contractility were evaluated by two-dimensional (2D) transthoracic echo cardiography in rabbits. The relationship between the left ventricular end-systolic wall stress (LVESWS) and the velocity of heart rate corrected circumferential fibre shortening (Vcfc) was used. Arterial blood pressure, heart rate, left ventricular pressure and transthoracic 2D echocardiographic data were determined at 1 MAC (minimum alveolar concentration) of halothane or isoflurane, both with 50% nitrous oxide. Drug-induced changes in pre-and afterload were performed in all study animals to assess the left ventricular contractile response over a wide range. LVESWS and Vcfc Were calculated on videotape recorded M-mode tracings.
Mean heart rate and arterial blood pressure were not significantly different between the two groups. Myocardial contractility under isoflurane/nitrous oxide anaesthesia was significantly higher than under halothane/nitrous oxide anaesthesia at 1 MAC. The results of the present study confirm data obtained from humans and other animal species and suggest that, in rabbits, myocardial contractility is best preserved by inhalation of isoflurane. Isoflurane should therefore be preferred over halothane, especially in cases of prolonged anaesthetic procedures.