Cardiopulmonary function in horses during anesthetic recovery in a hydropool

Objective-To determine the cardiovascular and respiratory effects of water immersion in horses recovering from general anesthesia. Animals-6 healthy adult horses. Procedure-Horses were anesthetized 3 times with halothane and recovered from anesthesia while positioned in lateral or sternal recumbency in a padded recovery stall or while immersed in a hydropool. Cardiovascular and pulmonary functions were monitored before and during anesthesia and during recovery until horses were standing. Measurements and calculated variables included 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 (ΔP_tpmax), total pulmonary resistance (R_L), dynamic compliance (C_dyn), and work of breathing (W). Results-Immersion in water during recovery from general anesthesia resulted in values of ABP, PAP, P_endXes, ΔP_tpmax, R_L, and W that were significantly greater and values of C_dyn that were significantly less, compared with values obtained during recovery in a padded stall. Mode of recovery had no significant effect on any other measured or calculated variable. Conclusions and Clinical Relevance-Differences in pulmonary and cardiovascular function between horses during recovery from anesthesia while immersed in water and in a padded recovery stall were attributed to the increased effort needed to overcome the extrathoracic hydrostatic effects of immersion. The combined effect of increased extrathoracic pressure and PAP may contribute to an increased incidence of pulmonary edema in horses during anesthetic recovery in a hydropool.