Evaluation of digital and laminar blood flow in horses given a low dose of endotoxin.
Authors: Ingle-Fehr, Baxter
Journal: American journal of veterinary research
Summary
# Editorial Summary: Digital and Laminar Blood Flow Response to Endotoxaemia Low-dose endotoxin challenge reliably induces the vascular changes associated with early laminitis, making it a valuable experimental model for understanding how systemic infection compromises foot perfusion. Using ultrasonic flowmetry around the palmar digital artery and laser Doppler probes inserted into the dorsal hoof wall, Ingle-Fehr and Baxter measured blood flow changes in six healthy horses over a four-hour period following intravenous endotoxin administration (0.1 µg/kg). Digital blood flow decreased significantly and more markedly than laminar perfusion, whilst heart rate and body temperature rose proportionally to clinical signs of endotoxaemia. The substantial drop in digital arterial flow—coupled with only modest reductions in actual tissue perfusion within the laminae—suggests that endotoxin-induced vasoconstriction preferentially affects the larger digital vessels, potentially creating a mismatch between proximal flow restriction and distal capillary perfusion. For practitioners, this work underscores why horses presenting with systemic infection warrant aggressive cardiovascular support and careful digital monitoring, as the lag between measurable decreases in large-vessel flow and clinically apparent laminar damage may provide a critical intervention window before irreversible vascular compromise develops.
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Practical Takeaways
- •Endotoxemia causes measurable reductions in blood supply to the digital tissues and hoof laminae, which may explain the increased risk of laminitis and other digit complications in systemically ill horses
- •Digital blood flow changes occur rapidly after endotoxin challenge and monitoring perfusion could help identify horses at high risk for secondary vascular complications
- •Preventive management of endotoxemia in colic and septic conditions becomes more critical given the documented acute vascular compromise at the digit level
Key Findings
- •Endotoxin administration (0.1 microgram/kg IV) caused a profound transient decrease in digital blood flow measured by ultrasonic flowmetry
- •Laminar perfusion decreased after endotoxin treatment, though the decrease was less substantial than digital blood flow reduction
- •Endotoxin treatment significantly increased heart rate and body temperature but saline control treatment caused no measurable changes
- •Horses with clinical endotoxemia demonstrated vascular alterations potentially predisposing to digit pathology