Cardiovascular and pulmonary effects of sevoflurane anesthesia in horses.

The research investigated the influence of varying doses of the anesthetic sevoflurane on the cardiovascular and respiratory function in horses. Results demonstrated that sevoflurane caused a decrease in cardiovascular activity, respiratory rate, and blood chemistry but didn’t significantly differentiate from other approved anesthetics.

Study Design and Variables

• The research conducted was an experimental study designed to measure the effects of different concentrations (1.0, 1.5, and 2.0 minimum alveolar concentration or MAC) of the anesthetic sevoflurane on several hemodynamic (related to the flow of blood), pulmonary (related to the lungs and respiration), and blood chemistry variables in healthy horses.
• Sevoflurane was the only anesthetic administered to the horses, and its effects were evaluated during both spontaneous and controlled ventilation, meaning conditions where the horses were either breathing naturally or where their breathing was controlled by the researchers, respectively.

Key Findings

• The research found that sevoflurane significantly decreased mean arterial blood pressure, cardiac output, and stroke volume in the horses in a dose-dependent manner. This means that these cardiovascular effects were directly related to the concentration of sevoflurane used.
• Additionally, as the sevoflurane concentration increased, the study found a non-significant trend towards decreased peripheral vascular resistance (resistance to blood flow in the blood vessels) and increased heart rate.
• Respiratory effects were also observed, with a dose-dependent decrease in respiratory rate associated with an increase in sevoflurane concentration. This decrease in breathing rate lead to a reduction in the total volume of gas exchanged per minute (minute volume). Increased concentration of sevoflurane also resulted in a significant rise in the tension of carbon dioxide in arterial blood.
• However, despite these observations, the research found that all blood chemistry values still remained within the normal physiological range, and there were no complications observed during the horses’ recovery from anesthesia.

Conclusions

• The study concluded that sevoflurane induces a dose-dependent decrease in cardiovascular and pulmonary function in horses, meaning these effects increase as the dose of the anesthetic increases.
• Importantly, though, these effects were not dramatically different from those induced by other approved inhalant anesthetics, suggesting a similar safety profile.