Aerosolized salbutamol (albuterol) improves PaO2 in hypoxaemic anaesthetized horses – a prospective clinical trial in 81 horses.

The study investigated the efficacy and impacts of salbutamol aerosol on hypoxaemic anaesthetized horses, indicating that such treatment could significantly improve the horses’ arterial oxygen tension without posing notable side-effects.

Research Objective

• The primary objective of this study was to evaluate the effects of aerosolized salbutamol (also known as albuterol) on the arterial pH, blood gas levels, heart rate, and mean arterial blood pressure in hypoxaemic (low arterial oxygen levels) anaesthetized horses.

Methodology

• The researchers selected 81 client-owned horses for the study, with weights varying between 114 and 925 kg. Fifty-seven of these horses had to undergo emergency abdominal surgery, whereas the remaining 24 were anaesthetized for elective procedures.
• The participating animals were premedicated with a combination of xylazine, detomidine, butorphanol, and morphine, then anaesthetized using guaifenesin and ketamine, diazepam, and ketamine, or guaifenesin and thiopental.
• All horses were intubated, with anesthesia maintained using either halothane or isoflurane in oxygen. The study followed continuous heart rate and rhythm monitoring and direct measurement of arterial blood pressure. Arterial blood gas and pH were also analyzed.
• When the arterial PaO (partial pressure of oxygen in the arteries) dropped below 70 mm Hg and didn’t respond to corrective measures, a salbutamol aerosol was administered through the endotracheal tube. A second blood sample was analyzed 20 minutes post-treatment.

Results

• The outcome showed no significant variations in mean arterial blood pressure, heart rate, arterial pH, base excess, and bicarbonate before and after the salbutamol treatment.
• The study found a significant increase in arterial oxygen tension from 62.4 ± 13.1 mm Hg pre-treatment to 119.4 ± 57.7 mm Hg post-treatment. There were also minor but significant reductions in PaCO (partial pressure of carbon dioxide in the blood) between sample times.
• No changes were observed in heart rhythm, although roughly 70% of the animals presented perspiration after the treatment.

Conclusions

• The study concluded that administering salbutamol aerosols to anesthetized horses exhibiting PaO values less than 70 mm Hg could lead to a near doubling of their PaO values within 20 minutes.
• The increase in PaO may have been due to bronchodilation and improved ventilation or increased perfusion caused by a rise in cardiac output, or potentially a combination of these factors. The exact reasoning was unclear as neither cardiac output nor ventilation-perfusion distribution were measured in the study.
• Overall, the study deemed salbutamol aerosols as potentially effective and simple technique to enhance PaO values in hypoxaemic horses during inhalant anaesthesia, without apparent detrimental side effects.