Effects of intramuscular administration of acepromazine on palmar digital blood flow, palmar digital arterial pressure, transverse facial arterial pressure, and packed cell volume in clinically healthy, conscious horses.
Authors: Leise Britta S, Fugler Lee Ann, Stokes Ashley M, Eades Susan C, Moore Rustin M
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Acepromazine remains a commonly used sedative in equine practice, yet its effects on digital haemodynamics warrant closer examination given the profession's concerns about laminitis risk. Leise and colleagues implanted Doppler flow probes and arterial catheters in 12 healthy horses to measure palmar digital blood flow, digital and facial arterial pressures, and packed cell volume over 6 hours following either 0.04 mg/kg intramuscular acepromazine or saline placebo. Whilst acepromazine-treated horses demonstrated statistically significant reductions in transverse facial arterial pressure and packed cell volume compared to controls, palmar digital arterial blood flow actually increased within the acepromazine group relative to baseline values—a finding that contradicts concerns about digital vasoconstriction. Critically, the magnitude of this blood flow increase in acepromazine-treated horses did not differ significantly from saline controls, suggesting the drug's vasodilatory effect on the digit is modest at best and occurs alongside systemic hypotension and mild haemodilution. For practitioners, these results indicate that whilst acepromazine's haemodynamic effects are measurable, they are unlikely to compromise digital perfusion acutely in healthy horses, though caution remains warranted in compromised individuals where baseline perfusion may already be marginal.
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Practical Takeaways
- •Acepromazine at standard sedative doses causes some reduction in blood pressure but does not dramatically compromise digital perfusion in healthy horses, making it relatively safe for routine use
- •The drug increases digital blood flow over time, which may have some benefit for horses with compromised circulation, but the effect is modest and not clinically significant compared to non-sedated states
- •Monitor for mild decreases in packed cell volume when using acepromazine, though this may be clinically insignificant in most cases
Key Findings
- •Acepromazine 0.04 mg/kg IM caused significant reduction in transverse facial arterial pressure compared to saline control
- •Palmar digital arterial blood flow increased significantly over 6 hours post-acepromazine administration compared to baseline, but was not significantly different from control group
- •Packed cell volume decreased significantly in acepromazine-treated horses compared to baseline values
- •Acepromazine produced only modest hemodynamic effects with minimal clinical sedation in healthy horses