Endotoxin-induced digital vasoconstriction in horses: associated changes in plasma concentrations of vasoconstrictor mediators.
Authors: Menzies-Gow N J, Bailey S R, Katz L M, Marr C M, Elliott J
Journal: Equine veterinary journal
Summary
# Editorial Summary Following endotoxin challenge, the digital vasculature undergoes profound constriction mediated by specific platelet-derived factors—a finding with direct implications for managing sepsis-related laminitis in clinical practice. Menzies-Gow and colleagues infused six Thoroughbreds with lipopolysaccharide (LPS) and simultaneously measured digital blood flow via Doppler ultrasonography alongside plasma concentrations of key vasoactive mediators including tumour necrosis factor alpha, serotonin (5-HT), thromboxane B₂ and endothelin. Digital arterial and venous blood flow decreased markedly (43% and 63% respectively) accompanied by falls in hoof wall and coronary band surface temperatures, yet crucially systemic blood pressure remained stable—indicating selective digital vasoconstriction rather than generalised circulatory shock. The temporal relationship between LPS exposure and subsequent rises in plasma 5-HT and thromboxane B₂ concentrations directly preceded the onset of digital hypoperfusion, whilst endothelin levels remained unchanged, suggesting platelet activation as the primary driver of the vascular response. These findings provide mechanistic support for anti-platelet interventions (aspirin, clopidogrel) in endotoxaemic horses at risk of laminitis, though the 20-year gap since publication warrants examination of whether this evidence base has been adequately translated into evidence-based prevention protocols in clinical settings.
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Practical Takeaways
- •Anti-platelet therapy may have a preventive role in managing laminitis secondary to endotoxemia or systemic infection
- •Digital vasoconstriction in septic/endotoxemic horses occurs through platelet-mediated mechanisms rather than systemic hemodynamic changes, suggesting local therapeutic targets
- •Monitor for digital cooling and reduced digital perfusion in horses with suspected endotoxemia as early signs of vasoconstriction-induced laminitis risk
Key Findings
- •LPS infusion reduced digital arterial blood flow by 43% and venous blood flow by 63% without altering systemic blood pressure
- •Plasma thromboxane B2 and serotonin (5-HT) concentrations increased coinciding with the onset of digital hypoperfusion
- •Plasma endothelin concentrations remained unchanged despite digital vasoconstriction, suggesting it is not the primary mediator
- •Temporal relationship between platelet-derived mediators (TxB2 and 5-HT) and digital hypoperfusion supports their role in LPS-induced laminitis