Cardiovascular and respiratory measurements in awake and isoflurane-anesthetized horses.

The research article covers an examination of the effects of isoflurane anesthesia on horses’ cardiovascular and respiratory function. Measurements were taken before, during, and after administering the anesthesia.

Research Methods

• The study involved monitoring seven nonmedicated, spontaneously breathing horses before, during, and an hour after they were put under anesthesia with 1.57% isoflurane in oxygen.
• The period of anesthesia lasted an average of 85 minutes, and changes in the animals’ circulatory and respiratory function were recorded and compared to their baseline (awake) state.

Major Findings

• Significant decreases in arterial blood pressure were noted after administering isoflurane anesthesia. These decreases were tied to slight but statistically insignificant drops in cardiac output and peripheral vascular resistance.
• While there was a noticeable decrease in stroke volume (the quantity of blood ejected by the heart in one heartbeat) due to the anesthesia and the horses’ lying down position, this did not cause a meaningful decrease in cardiac output as the heart rate tended to increase.
• The anesthesia also caused significant increases in the levels of carbon dioxide in arterial blood (PaCO2), peak expiratory gas flow, total expiratory time, and packed cell volume (PCV).
• On the other hand, levels of oxygen in arterial blood (PaO2), the volume of gas expired per minute, and the ratio of peak inspired to expired gas flow were significantly reduced.
• The changes caused by the anesthesia were reversed approximately 1.5 hours post-anesthesia.

Implications

• The findings imply that isoflurane anesthesia alters the cardiovascular and respiratory functions of horses significantly. These alterations, however, are temporary and tend to subside approximately 1.5 hours after the administration of the anesthesia.
• The observed changes need to be considered when administering isoflurane anesthesia to horses, especially pertaining to animals with pre-existing cardiovascular or respiratory conditions. The effects could potentially be more harmful for these animals, as their physiological functions might already be compromised.
• This study contributes to existing literature on the short-term physiological impacts of anesthesia on veterinary patients and can help inform safer and more efficient anesthetic practices in horses.