Cardiopulmonary function in horses during anesthetic recovery in a hydropool.

The research investigated the impact of water immersion on horses during their recovery from general anesthesia, focusing on cardiovascular and respiratory effects. The findings suggested increased pulmonary and cardiovascular strain due to the added effort of overcoming extrathoracic hydrostatic pressure when horses recover while immersed in water.

Research Methodology

• The study involved six healthy adult horses. Each horse was anesthetized three times using a drug named halothane.
• For their recovery from the anesthesia, the horses were positioned in two different ways for each recovery session: in lateral or sternal recumbency in a padded recovery stall, or immersed in water in a hydropool. This allowed the researchers to compare the cardiovascular and pulmonary effects under different conditions.
• The scientists monitored multiple aspects of the horses’ cardiovascular and pulmonary functions both before and during anesthesia, and throughout the recovery until the horses could stand up. This included measurements of carotid and pulmonary arterial blood pressures (ABP and PAP respectively), cardiac output, heart and respiratory rates, arterial and mixed venous blood gases, minute ventilation, end expiratory transpulmonary pressure (P(endXes)), maximal change in transpulmonary pressure (deltaP(tp)max), total pulmonary resistance (RL), dynamic compliance (Cdyn), and the work of breathing (W).

Key Findings

• The results suggested that when horses were recovering from anesthesia while immersed in water, certain measured values significantly differed from the measurements taken when the horses were recovering in a padded stall. ABP, PAP P(endXes), deltaP(tp)max, RL, and W were significantly higher, while Cdyn was significantly lower.
• However, the mode of recovery did not significantly affect any other measured or calculated variable.

Conclusion

• The variances in the horses’ pulmonary and cardiovascular functions during the recovery from anesthesia while being immersed in water, compared to a regular padded recovery stall, were attributed to the increased effort required to overcome the hydrostatic effects of water immersion.
• An interesting implication of this research is that the combined effect of this increased extrathoracic pressure and PAP might increase the risk of developing pulmonary edema in horses during anesthetic recovery in a hydropool. More research is needed to substantiate this observation.