Cardiovascular effects of continuous propofol infusion in horses.

This research examined how continuous infusion of propofol, a commonly used anesthetic, affects the cardiovascular system of horses. They found that while some measures such as stroke volume decreased significantly with higher doses, others including mean arterial pressure and cardiac output did not change significantly, suggesting that propofol may be used for long-term anesthesia in horses.

Introduction

• The study aimed to investigate the impact of continuous infusion of propofol, a popular anesthetic drug used in both human and veterinary medicine, on various parameters of the cardiovascular system in horses.
• Horses were given propofol at different dose rates including 0.14, 0.20, and 0.30 mg/kg/min. The cardiovascular markers measured were heart rate, mean arterial pressure, mean right atrial pressure, stroke volume, cardiac output, systemic vascular resistance, pre-ejection period, and ejection time.

Methods

• To maintain consistency in ventilation conditions during the process of propofol infusion, the technique of intermittent positive pressure ventilation was employed. This method helped in keeping the partial arterial CO(2) pressure within the range of 45 to 55 mmHg during the anesthesia maintenance period.

Findings

• The study’s findings revealed a significant dose-dependent decrease in stroke volume, indicating a reduced cardiac contractility during continuous propofol infusion, i.e., the heart’s capacity to contract and pump decreases as the doses of propofol increase.
• Although stroke volume declined, cardiac output did not show significant changes. This is an interesting finding given that cardiac output (the quantity of blood the heart pumps per minute) is usually related to stroke volume.
• Systemic vascular resistance, a measure of resistance or opposition to blood flow in blood vessels, significantly decreased at higher doses.
• The study also found that the pre-ejection period was prolonged and the pre-ejection period to ejection time ratio increased significantly at the highest doses of propofol infusion. The ejection time refers to the time span during which the heart contracts and blood is forced out into the aorta.

Conclusion

• Overall, the data suggested that while propofol infusion does have some impact on the cardiovascular system of horses, it may still be used for long-term anesthesia as mean arterial pressure and cardiac output did not show significant alterations. Cardiac output and mean arterial pressure are critical indicators of cardiovascular health. Therefore, their stability under continuous propofol infusion indicates the potential feasibility of using this anesthetic for prolonged periods in horses.