The effect of lateral and dorsal recumbency on cardiopulmonary function in the anaesthetised horse.

This research conducted an comparison examining how placing horses on their sides (lateral recumbency) versus on their backs (dorsal recumbency) impacts their heart and lung function while they’re under anesthesia. The study assessed variables like cardiac output and lung ventilation and found significant changes based on the horse’s positioning.

Research Details and Methodology

• The researchers aimed to understand the effects of two positions, lateral (on the side) and dorsal (on the back), on the functioning of the cardiopulmonary system (heart and lungs) in anaesthetised horses. The positions of the horses while anaesthetised can play a significant role in their cardiopulmonary function.
• The research involved six horses as study subjects. The team measured several factors, including cardiac output per kilogram (the amount of blood the heart pumps each minute per kg of the horse’s weight), stroke volume per kilogram (the amount of blood the heart pumps out with each beat per kg of the horse’s weight), alveolar ventilation (how quickly the lungs take in and expel air), venous admixture, pulmonary shunt (blood flow deviation in the lungs), and blood-gas values.

Results and Findings

• When the horses moved from a lateral to a dorsal position, the research observed a non-significant decrease in cardiac output per kilogram. This means that the change in position did not drastically affect the amount of blood pumped by the heart.
• However, a significant increase in the pulmonary shunt was observed. This situation can potentially disrupt lung function and oxygen supply to the body since pulmonary shunt refers to a condition in which blood does not exchange gas with air in the lungs and goes back into circulation without receiving oxygen.
• The study also found a positive correlation between body mass and the pulmonary shunt when the horse was in dorsal recumbency. Meaning, larger bodied horses may have exhibited higher rates of pulmonary shunt when positioned on their backs.
• Alveolar ventilation rates increased significantly in dorsal recumbency when the horses were breathing air compared to oxygen. Hence, there was improved ventilation while the horses were on their backs breathing regular air than oxygen.

Implications of Research

• The findings of the research have important implications for the anaesthesia practices in horses, particularly in relation to their positioning. It helps in understanding the impacts of different positions on critical functions of the horses under anaesthesia, which can have significant effects on the horse’s health and recovery.
• Being aware that pulmonary shunt significantly increases when the horse is in dorsal recumbency, veterinary anaesthetists can plan their strategies more effectively, such as choosing lateral recumbency or ensuring oxygen supply during and post anaesthesia, especially in larger horses.