Evaluation of digital hemodynamics associated with black walnut‐induced equine laminitis using colored isotopic‐labeled microspheres

Abstract

There is substantial evidence suggesting local digital hemodynamic alterations occur in equine laminitis; however, direct measurement of tissue perfusion is limited due to the anatomic location between the hoof and bone. The use of colored microspheres allows for differentiation between flow through the laminar capillaries and flow bypassing the laminae via arteriovenous shunts (AVAs). The objective was to measure serial perfusion alterations in the equine digit using microspheres. Acute laminitis was induced in 13 clinically healthy horses using black walnut extract (BWE). Before, and at specified times after BWE, microspheres were injected into one forelimb digital artery with subsequent withdrawal of digital venous blood. Hemodynamics, hematological parameters, and clinical signs were monitored for 72 hours in all horses. A hyperemic period occurred 8–72 hours post-BWE administration. Microspheres present in the palmar digital venous circulation decreased with the development of BWE-induced laminitis and serve as an indication of AVAs within the digital circulation. In our study, microspheres in digital venous blood decreased with laminitis suggesting AVAs close during laminitis. In summary, the alterations in microsphere values within the palmar digital blood and laminar tissues suggest altered digital circulation and perfusion during the developmental and early stages of BWE-induced laminitis. Funding by Grayson Jockey Club Research Foundation.