Laboratory animals
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The effects of a rapid increase in inspired desflurane concentration on systemic haemodynamics and plasma catecholamines were studied in seven pigs (22-30 kg). Following premedication (flunitrazepam 0.4 mg/kg i.m.), anaesthesia was induced (propofol 2.5 mg/kg i.v., vecuronium 0.2 mg/kg i.v.), the trachea orally intubated, and ventilation controlled. Anaesthesia was maintained with N2O/O2 (70%/30%), propofol (50 micrograms/kg/min), desflurane (2% end-tidal concentration), and vecuronium (0.3 mg/kg/h). ⋯ There was an immediate decrease in MAP. Plasma levels of E and NE remained unchanged throughout. In conclusion, in contrast to findings in humans, a rapid increase in inspired desflurane concentration does not cause a hyperdynamic circulatory response in the pig.
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Comparative Study
Effects of isoflurane versus halothane on myocardial contractility in rabbits: assessment with transthoracic two-dimensional echocardiography.
The effects of isoflurane versus halothane on cardiac contractility were evaluated by two-dimensional (2D) transthoracic echocardiography 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 echocardiogrphic data were determined at 1 MAC (minimum alveolar concentration) of halothane or isoflurane, both with 50% nitrous oxide. ⋯ 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.
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Endotracheal intubation allows precise delivery of inhaled anaesthetic agents. Intubation in small non-human primates (less than 1 kg), is straightforward, using commercially available equipment, and careful positioning of the animal. Equipment and methods are fully described and illustrated.
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Endotracheal intubation of rabbits is reported, both personally and in the literature, to be so difficult that special equipment has been constructed by other workers to facilitate the procedure. We report that the positioning of the operator, behind the animal, viewing from the dorsal surface of the head, facilitates this procedure enormously.
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Comparative Study
Induction of anaesthesia with halothane and isoflurane in the rabbit: a comparison of the use of a face-mask or an anaesthetic chamber.
The effects of induction of anaesthesia with halothane or isoflurane were studied in rabbits. The anaesthetic agents were delivered either via a face-mask, or the animals were placed in an anaesthetic induction chamber. ⋯ The combination of bradycardia and hypercapnia during induction may represent an increased risk of anaesthetic associated mortality. Animals in all groups tried to avoid inhaling anaesthetic vapour, and this behaviour, together with the occurrence of breath-holding suggests that induction was aversive.