Effects of long-term extracorporeal blood perfusion of the distal portion of isolated equine forelimbs on metabolic variables and morphology of laminar tissue

Abstract

Objective - To establish an ex vivo model of blood perfusion in the distal portion of isolated equine forelimbs that closely represents the in vivo situation in the laminar tissue of the hoof. Sample Population - 18 forelimbs collected from 9 healthy adult horses following slaughter at a licensed abattoir. Procedures - The distal portion of isolated equine forelimbs from 9 horses were perfused under physiologic conditions over a period of 6, 8, and 10 hours with autologous blood. To determine cell viability in perfused tissues, indicators for metabolism (lactate generation and glucose and oxygen consumption) as well as indicators for cell damage (potassium concentration and lactate dehydrogenase activity) were examined at 1-hour intervals from samples of the perfusate. Weight gain in the forelimb was used to determine the edema index. After perfusion, light and electron microscopic examinations of laminar tissue specimens were performed. Results - During hemoperfusion of the isolated forelimbs, mean ± SD glucose consumption was 197.4 ± 65.1 mg/h, lactate generation was 1.84 ± 0.79 mmol/h, and oxygen consumption was 6.4 × 10-6 ± 8.9 × 10-5 mL·g-1·min-1. Neither an efflux of potassium into the perfusate nor a relevant increase of the lactate dehydrogenase activity was detected, indicating low amounts of cellular damage in the perfused tissues. Weight gain of forelimbs was 1.02 ± 0.95%. Histologic and ultrastructural appearance of the laminar tissue revealed no signs of tissue damage. Conclusions and Clinical Relevance - Isolated equine limbs were perfused under physiologic conditions over a period of ≤ 10 hours without structural damage to the laminar tissue.