Comparison of inhaled salbutamol and salmeterol for the treatment of arterial hypoxaemia in anaesthetized horses: a randomized clinical trial.

This research investigated the efficacy of two inhalants, salbutamol and salmeterol, for treating low levels of oxygen in the blood (arterial hypoxaemia) in horses under anaesthesia. The study found that inhaled salbutamol was more effective than salmeterol in improving oxygen levels.

Methodology

In their study, the researchers used a total of 108 client-owned horses which were categorized based on the American Society of Anesthesiologists’ status from I-V. These horses were to undergo elective and emergency procedures. The anaesthesia procedure was structured as follows:

• The horses were first premeditated using acepromazine (given either intramuscularly 0.1 mg kg or intravenously 0.05 mg kg) and xylazine (0.6 mg kg IV).
• Then, a combination of midazolam (0.06 mg kg IV) and ketamine (2.2 mg kg IV) was administered to induce anaesthesia.
• An isoflurane in an oxygen/air mixture (with an inspired oxygen fraction of 0.7) was used for maintaining anaesthesia.
• Mechanical ventilation was commenced promptly with specific settings.

If the PaO (arterial partial pressure of oxygen) reading was less than 100 mmHg, then the horses were randomly selected to get either inhaled salbutamol (2 μg kg) or salmeterol (0.5 μg kg).

Results

The research findings showed differing results for the two substances. For instance:

• Out of the 108 horses, 60 received salbutamol. At the 15 and 30-minute mark, approximately 65% and 60% respectively experienced success after treatment, marking an observable increase in their initial PaO levels by 38% and 44%.
• The remaining 48 horses were given salmeterol of which only 35% showed improvement at both 15 and 30 minutes, increasing their initial PaO level by only 3% and 4% respectively.
• PaO was found to significantly increase following salbutamol administration than after salmeterol at both time intervals.

Conclusions

The study concluded that, within the conditions described in the study protocol, inhaled salbutamol effectively increased PaO levels to a greater extent than salmeterol in anaesthetized horses with an initial reading of less than 100 mmHg. Therefore, for horses under anaesthesia with arterial hypoxaemia, salbutamol might serve as a more effective treatment.