A comparison of seven methods for continuous therapeutic cooling of the equine digit

REASONS FOR PERFORMING STUDY: Digital hypothermia may be effective for laminitis prophylaxis and therapy, but the efficacy of cooling methods used in clinical practice requires evaluation. OBJECTIVES: To use hoof wall surface temperature (HWST) to compare several cooling methods used in clinical practice. STUDY DESIGN: Experimental crossover design with a minimum washout period of 72 h. METHODS: Seven cooling methods (commercially available ice packs, wraps and boots) and one prototypical dry-sleeve device were applied to a single forelimb in 4 horses for 8 h, during which HWST of the cooled forelimb and the uncooled (control) forelimb was recorded hourly. Results were analysed descriptively. RESULTS: The median (range) HWST from 2-8 h was lowest for the ice and water immersion methods that included the foot and extended proximally to at least include the pastern: 5.2°C (range: 4.8-7.8°C) for the fluid bag and 2.7°C (2.4-3.4°C) for the ice boot. An ice boot that included the distal limb but not the foot resulted in a median HWST of 25.7°C (20.6-27.2°C). Dry interface applications (ice packs) confined to the foot only resulted in a median HWST of 21.5°C (19.5-25.5°C) for the coronet sleeve and 19.8°C (17.6-23°C) for a commercial ice pack. For the dry interface applications that included the foot and distal limb, the median HWST was much higher for the ice pack device, 19.9°C (18.7-23.1°C), compared with the perfused cuff prototype of 5.4°C (4.2-7°C). CONCLUSIONS: Immersion of the foot and at least the pastern region in ice and water achieved sustained HWST <10°C as did a prototype perfused cuff device with a dry interface. Variation between cooling methods may have a profound effect on HWST and therefore efficacy in clinical cases where laminitis prophylaxis or therapy is the goal.