Effects of weight bearing and thermal conditions on equine digital hemodynamics

Abstract

Laminitis, a common equine disease, can develop secondary to painful contralateral limb conditions (i.e. Kentucky Derby winner 'Barbaro'). It is hypothesized that blood flow alterations, laminar structural failure (from excessive weight), or a combination are responsible.The goals were to examine the effects of weight‐bearing and thermal conditions on equine digital hemodynamics.8 horses were instrumented with a Doppler ultrasonic probe around the palmar digital artery and catheters in the palmar artery and digital vein. We measured digital hemodynamics and administered 15 um isotopic microspheres into the palmar arterial circulation under these conditions:Weight equally‐balancedWeight off of instrumented leg (zero loading)Weight on instrumented leg (full loading)Normal hoof temperature (32 ° C)Cold hoof temperature (10 ° C)Warm hoof temperature (54 ° C)There was a significant effect of weight and temperature on laminar microspheres (p < 0.0001). This data demonstrates full loading results in decreased laminar perfusion. Additionally, ice therapy decreases and warm therapy increases perfusion. Interestingly, blood flow at the fetlock level, palmar arterial and digital venous pressures did not change. This demonstrates weight‐bearing and thermal conditions change blood flow reaching the laminar tissues and change the state of arteriovenous anastomoses.Funding by Morris Animal Foundation.