A comparison of the haemodynamic effects of isoflurane and halothane anaesthesia in horses.
Authors: Raisis A L, Young L E, Blissitt K J, Brearley J C, Meire H B, Taylor P M, Lekeux P
Journal: Equine veterinary journal
Summary
# Isoflurane versus Halothane Anaesthesia in Horses: Haemodynamic Comparison Inhalational anaesthetic choice significantly impacts cardiovascular function in horses, yet evidence comparing equipotent doses of isoflurane and halothane under standardised conditions remains limited. This investigation systematically evaluated six adult horses across two separate anaesthetic episodes, maintaining isoflurane at 1.3–1.4% end-tidal concentration and halothane at 0.9–1.0%, with comprehensive haemodynamic monitoring via transoesophageal Doppler echocardiography, arterial catheterisation, and laser Doppler flowmetry of hindlimb musculature. Isoflurane demonstrated superior left ventricular function across multiple parameters—including significantly higher cardiac output, maximal aortic velocity, stroke volume integral, and rate of ventricular pressure rise—alongside lower systemic vascular resistance and reduced diastolic aortic pressure compared to halothane, despite concurrent use of romifidine premedication and ketamine induction. Peripheral perfusion also favoured isoflurane, with substantially greater femoral arterial and venous blood flow alongside lower pulsatility indices and early diastolic deceleration slopes. For equine practitioners selecting maintenance anaesthetics, these findings reinforce that isoflurane preserves cardiovascular stability and peripheral tissue perfusion more effectively than halothane, supporting its preferential use in clinical cases where maintaining haemodynamic integrity is paramount—particularly in compromised patients where reduced systemic vascular resistance and improved myocardial contractility carry meaningful prognostic advantages.
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Practical Takeaways
- •Isoflurane provides superior cardiovascular stability and haemodynamics compared to halothane in equine anaesthesia, maintaining better cardiac output and systemic perfusion
- •When anaesthetising horses, isoflurane offers advantages for patients at cardiovascular risk, as it preserves left ventricular function better than halothane despite using potent premedication
- •Peripheral blood flow to hindlimbs is better maintained with isoflurane, which may be clinically relevant for preventing postoperative complications related to regional ischaemia
Key Findings
- •Isoflurane anaesthesia resulted in significantly higher cardiac output, maximal aortic blood flow velocity, and left ventricular contractility (LVdp/dt max) compared to halothane at all measured time points
- •Systemic vascular resistance was significantly lower during isoflurane anaesthesia, with reduced pre-ejection period and diastolic aortic blood pressure compared to halothane
- •Femoral arterial and venous blood flow were significantly higher during isoflurane with lower pulsatility index and early diastolic deceleration slope compared to halothane
- •Improved left ventricular systolic function with isoflurane persisted despite premedication with romifidine and ketamine induction, suggesting agent-specific rather than premedication-dependent effects