The effect Dobutamine and Bolus crystalloid fluids on the cardiovascular function of isoflurane anaesthetised horses

Loughran, Claire (2016) The effect Dobutamine and Bolus crystalloid fluids on the cardiovascular function of isoflurane anaesthetised horses. Masters by Research thesis, Murdoch University.

Abstract

Reason for performing the study: Cardiac output does not always increase with dobutamine administration in anaesthetised horses and information on peripheral perfusion is lacking.

Objective: Determine the effect of intravenous dobutamine infusion with and without a concurrent 20 mL kg-1 bodyweight bolus of crystalloid fluids on the cardiovascular function of hypotensive, isoflurane-anaesthetised horses premedicated with acepromazine.

Study design: Prospective, randomised, crossover experimental design.

Methods: Six horses aged 5-13 years, weighing 464-578 kg were premedicated with acepromazine 0.02 mg kg-1, then sedated with xylazine 0.8 mg kg-1 intravenously. Anaesthesia was induced with ketamine 2.2 mg kg-1 and diazepam 0.08 mg kg-1 intravenously and maintained in lateral recumbency with isoflurane, adjusted to achieve a target mean arterial pressure (MAP) (60mmHg+/-5%) 60 minutes post-induction of anaesthesia (T0). One of two randomly allocated treatments was then given. In treatment D, dobutamine was initially infused at 0.5 μg kg-1 min-1 and adjusted to achieve a target MAP (80 mmHg +/- 5%) within 30 minutes of infusion initiation. In treatment D+F dobutamine was administered as described for treatment D, with 20 mL kg-1 bodyweight Hartmann’s solution infused intravenously over 20 minutes. Cardiac index (CI), haemoglobin concentration ([Hb]), arterial oxygen content (CaO2), oxygen delivery index (DO2I) and bilateral femoral arterial blood flow (FBF) were recorded at T0, 30 minutes following dobutamine initiation (T1) and 15 minutes following dobutamine cessation (T2). Data were analysed using a mixed effect linear model (P<0.05 considered significant) and presented as mean +/- 95% confidence intervals.

Results: During treatment D, a significant increase was observed in DO2I, CaO2 and [Hb] between T0 and T1. While CaO2 and [Hb] remained significantly higher at T2 compared to T0, DO2I at T2 was not significantly different from T0. During treatment D+F a significant increase was observed in FBF between T0 and T1. However FBF at T2 was not significantly different from T0. A significant difference between treatments was recorded at T1 for [Hb] and CaO2 and at T2 for [Hb]. There was no change in CI during either treatment.

Conclusion: Administration of dobutamine alone significantly increased DO2I while coadministration of dobutamine and fluids did not. In contrast co-administration of crystalloid fluids and dobutamine significantly increased FBF, while dobutamine alone did not.

Item Type:	Thesis (Masters by Research)
Murdoch Affiliation(s):	School of Veterinary and Life Sciences
Notes:	Research Masters with Training
Supervisor(s):	Raisis, Anthea
URI:	http://researchrepository.murdoch.edu.au/id/eprint/32825

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