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

Abstract

OBJECTIVE: To compare the efficacy of inhaled salbutamol with salmeterol for the treatment of arterial hypoxaemia in anaesthetized horses. STUDY DESIGN: Prospective, randomized, clinical study. ANIMALS: A total of 108 client-owned horses (American Society of Anesthesiologists status I-V) anaesthetized for elective and emergency procedures. METHODS: Horses were premedicated with acepromazine [intramuscularly 0.1 mg kgor intravenously (IV) 0.05 mg kg] and xylazine (0.6 mg kgIV). Midazolam (0.06 mg kgIV) and ketamine (2.2 mg kgIV) were combined to induce anaesthesia, and isoflurane in oxygen/air mixture (inspired oxygen fraction 0.7) was used for maintenance of anaesthesia. Mechanical ventilation was initiated without delay using the following ventilator settings: tidal volume 10 mL kg, respiratory rate 8 breaths minute, inspiratory-to-expiratory time ratio 1:2, no positive end-expiratory pressure. If arterial blood gas analysis revealed PaO< 100 mmHg (13.3 kPa), the administration of either inhaled salbutamol (2 &#x3bc;g kg) or salmeterol (0.5 &#x3bc;g kg) was randomly assigned Blood gas analysis was repeated 15 and 30 minutes after treatment. The intervention was considered successful when PaOafter treatment &#x2265; 1.2&#xa0;&#xd7; PaObefore treatment (i.e. &#x2265;20% increase). PaOat 15 and 30 minutes was compared between groups using Mann-Whitney U test; p < 0.05 was considered significant. RESULTS: Of the 108 horses, 60 were administered salbutamol, 65% and 60% responded successfully at 15 and 30 minutes, increasing their initial PaOby 38% and 44%, respectively. The other 48 horses were administered salmeterol, 35% responded successfully at 15 and 30 minutes, increasing their initial PaOby 3% and 4%, respectively. PaOwas significantly higher after salbutamol than after salmeterol at 15 and 30 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: Using the described protocol, inhaled salbutamol was more effective than salmeterol in improving PaOin anaesthetized horses with value < 100 mmHg (13.3 kPa).