Cardiopulmonary effects of desflurane in horses.

The research investigates the effects of a type of anaesthetic called desflurane (DES) on the heart rate and lung function of horses. The study found that specific concentrations of DES can alter heart rate, respiratory rate, and minute volume, but doesn’t have a significant impact on mean arterial pressure in horses.

Research Methodology

• The study was conducted on six healthy adult horses, of both genders, aged roughly 9 years, and weighing around 370kg.
• Anesthesia for the horses was induced with a mixture of oxygen (O2) and DES, being delivered at a rate of 10 liters per minute.
• The horses were intubated and placed on their right side. Anesthesia was maintained with a mixture of DES and oxygen, administered through a large animal circular breathing system.
• The researchers established the minimum concentration of DES necessary to prevent the horses from responding to an electrical stimulus applied for one minute to their oral mucous membranes. This measure is called the Minimum Alveolar Concentration (MAC) of DES.
• The concentration of DES was then increased to reach end-tidal concentrations equivalent to 1.5 times, 1.75 times, and twice the MAC of DES for each horse.
• At each concentration level, the heart rate, mean arterial blood pressure, respiratory rate, tidal volume, minute volume, and core temperature were measured. Arterial blood gas analysis was conducted using blood samples.
• Statistical analysis of all collected data was done using two-way anova for repeated measures and Fisher’s test for multiple comparisons. A statistical threshold of p<0.05 was applied for significance.

Research Findings

• DES concentrations at twice the MAC increased the heart rate of the horses, while lower concentrations did not show an effect on the heart rate.
• Mean arterial pressure in the horses did not change at DES concentrations up to 1.75 times the MAC but showed a decrease at twice the MAC.
• All tested DES concentrations significantly reduced the respiratory rate, tidal volume, and minute volume in the horses. Tidal volume refers to the volume of air displaced from the lungs during normal respiration, while minute volume relates to the total volume of air breathed in one minute.
• The main finding concluded that concentrations of DES between 1.0 and 1.75 times MAC reduce respiratory rate and minute volume, but do not meaningfully affect the heart rate or mean arterial pressure in horses.