The relationship between digital perfusion pressure and hoof lamellar blood flow in isoflurane-anesthetized horses

Digital perfusion pressure (DPP) equals mean arterial pressure (MAP) at the hoof coronet minus digital interstitial pressure (DIP) within the hoof. To test whether lamellar blood flow (LBF) changes proportionately to DPP, anesthesia was induced and maintained with isoflurane in six horses to target a MAP of 60 mmHg. Arterial, venous, and hoof interstitial pressures were measured in each pelvic limb. LBF was measured using fluorescent microspheres during dobutamine infusions targeting either 60 (low), 80 (medium), or 100 (high) mmHg MAP. Following euthanasia, hoof lamina was collected for microsphere isolation. To reduce intra-individual variability, medium and high pressures and flows were divided by their respective low pressure and flow baseline values, yielding indexed variables of ΔLBF and ΔDPP. The ΔLBF correlated negatively with the ΔDPP. We conclude that LBF was not solely determined by passive pressure-flow relationships and that systemic hypertension may not effectively increase dermal LBF in horses.