Examining the arrhythmogenicity of dobutamine when used in conjunction with isoflurane in horses: A retrospective study at a single university teaching hospital.

Background: Dobutamine is used to treat hypotension in isoflurane-anaesthetised horses but may produce arrhythmias. Halothane is a volatile anaesthetic that was, historically, widely used in horses, but in one study, 56 of 200 halothane-anaesthetised horses (28%) developed arrhythmias after dobutamine administration. Although isoflurane has largely replaced halothane, it is unknown how isoflurane and dobutamine interact in the development of arrhythmias.

Methods: The medical records of horses undergoing general anaesthesia at the University of Georgia Veterinary Teaching Hospital in 2015 were reviewed retrospectively. Cases were selected if isoflurane was used as the maintenance inhalant anaesthetic agent and dobutamine was administered for the treatment of hypotension. Any instances of arrhythmia occurring following dobutamine administration were recorded.

Results: Arrhythmia occurred after dobutamine administration in six out of a total of 148 horses (4.0%).

Limitations: The retrospective nature of this study and the fact that the horses were anaesthetised at a single institution might limit the extent to which the findings can be generalised.

Conclusion: Compared to halothane, isoflurane has a much lower incidence of arrhythmia when used with dobutamine. However, a larger-scale study is needed to identify risk factors associated with horses developing an arrhythmia induced by isoflurane in combination with dobutamine.