Effect of protective padding on forelimb intracompartmental muscle pressures in anesthetized horses.

This research study investigates the effect of different contact surfaces (concrete, foam rubber, an air dunnage bag, and a water mattress) on the pressure inside the muscles of anesthetised horses. Findings suggest that the choice of surface affects pressure levels, potentially elevating the risk of muscle damage or blood flow obstruction.

Objectives and Methodology

• The study aimed to understand the impact of different padding surfaces used during anesthesia on intracompartmental muscle pressures in the forelimbs of horses.
• Eight horses maintained under halothane anesthesia, with controlled breathing brought about by intermittent positive-pressure ventilation, were used for the study.
• Each horse’s triceps brachii and extensor carpi radialis muscles’ intracompartmental pressures were measured using Wick catheters.
• The horses were positioned in left lateral recumbency and were sequentially placed on four contact surfaces: concrete, foam rubber, air dunnage bag, and a water mattress, for an hour each.
• Several medical parameters were monitored including blood gas, cardiac output, and blood pressure to ensure consistent anesthesia.
• Hematologic and biochemical assessments were made before and 24 hours after the anesthesia to identify potential effects.

Findings and Conclusions

• The results showed that intracompartmental muscle pressures increased considerably in the muscle bellies of the lower limb for all horses.
• Out of all four surfaces tested, supporting the horse on a water mattress led to the least pressure elevation, whereas a foam surface caused the maximum pressure increase.
• The excessive intracompartmental muscle pressures observed could cause the triceps muscle, and to a lesser extent, the extensor carpi radialis muscle, to be subject to ischemia due to the likely exceedance of the critical closing pressure of 30 mm of Hg required for capillary blood flow.
• This study suggests that the type of padding used to support anesthetized horses can significantly affect the risks faced related to blood flow obstruction and muscle damage, and it further stresses the importance of the choice of contact surface.