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Cardiovascular function during maintenance of anaesthesia with isoflurane or alfaxalone infusion in greyhounds experiencing blood loss

Raisis, A.L., Smart, L., Drynan, E. and Hosgood, G. (2015) Cardiovascular function during maintenance of anaesthesia with isoflurane or alfaxalone infusion in greyhounds experiencing blood loss. Veterinary Anaesthesia and Analgesia, 42 (2). pp. 133-141.

Link to Published Version: http://dx.doi.org/10.1111/vaa.12190
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Abstract

Objective: To compare adequacy of oxygen delivery and severity of shock during maintenance of anaesthesia with isoflurane or alfaxalone infusion in greyhounds experiencing blood loss. Study design: Prospective, randomised study. Animals: Twenty-four greyhounds (ASA I). Methods: All greyhounds were premedicated with methadone (0.2 mg kg-1) intramuscularly. Anaesthesia was induced with alfaxalone 2.5 mg kg-1intravenously. Following endotracheal intubation, the dogs were connected to an anaesthetic circle circuit delivering oxygen. Dogs were allocated to receive inhaled isoflurane or an intravenous infusion of alfaxalone for maintenance of anaesthesia. Isoflurane was initially administered to achieve an end-tidal concentration of 1.4% and alfaxalone was initially administered at 0.13 mg kg-1 minute-1. The dose of isoflurane or alfaxalone was adjusted during instrumentation to produce a clinically equivalent depth of anaesthesia. All dogs were mechanically ventilated to normocapnia (PaCO2 35-40 mmHg; 4.67-5.33 kPa). Passive warming maintained core body temperature between 37 and 38 °C. Measured and calculated indices of cardiovascular function, including mean arterial blood pressure (MAP), cardiac index (CI), systemic vascular resistance index (SVRI), oxygen delivery index (ḊO2I), oxygen consumption index (V̇O2I) and oxygen extraction ratio (OER), were determined at baseline (60 minutes after start of anaesthesia) and after removal of 32 mL kg-1and 48 mL kg-1of blood. Results: In all dogs, blood loss resulted in a significant decrease in MAP, CI, ḊO2, and a significant increase in SVRI, V̇O2I, and OER. The changes in each of the indices did not differ significantly between dogs receiving isoflurane and dogs receiving alfaxalone. Conclusion and clinical relevance: No difference in oxygen delivery or severity of shock was observed when either inhaled isoflurane or intravenous alfaxalone infusion was used for maintenance of anaesthesia in greyhounds experiencing blood loss. There appears to be no clinical advantage to choosing one anaesthetic agent for maintenance of anaesthesia over the other in a dog experiencing blood loss.

Publication Type: Journal Article
Murdoch Affiliation: School of Veterinary and Life Sciences
Publisher: Blackwell Publishing Inc.
Copyright: © 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.
URI: http://researchrepository.murdoch.edu.au/id/eprint/22937
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