The Effect of Inhaled Albuterol on PaO₂ in Anesthetized Horses Receiving a FiO₂ of 0.5 or >0.95

Impairment of oxygen uptake can occur during general anesthesia in horses resulting in hypoxemia. Multiple treatments have been investigated for correction of hypoxemia with varying levels of success. In clinical trials, albuterol, a short-acting β₂ adrenergic agonist, improved arterial oxygen partial pressure (PaO₂) in anesthetized horses unresponsive to adjustments in mechanical ventilation and administration of positive inotropic drugs. However, controlled studies comparing the magnitude of change and duration of effect of albuterol on PaO₂ in healthy, nonhypoxemic anesthetized horses are lacking. In a prospective study, 14 horses were anesthetized and received a FiO₂ of 0.5 (n = 7) or > 0.95 (n = 7). Horses were maintained on isoflurane and mechanically ventilated. After 15 minutes, baseline PaO₂ was determined. Within each FiO₂ group, five horses were administered inhaled albuterol (2 µg/kg) and two horses received no treatment. At 10, 20, 30, and 40 minutes after baseline, PaO₂ was measured. Data for horses that received albuterol were analyzed with repeated measures analysis of variance with significance at P < .05. Horses that received albuterol had an increase in PaO₂ for at least 40 minutes after baseline. Albuterol administered via inhalation, was associated with an increased PaO₂ of at least 40 minutes compared to baseline in healthy, nonhypoxemic horses undergoing anesthesia at similar depth, using a FiO₂ of 0.5 and > 0.95. Side effects were mild and consisted of increased heart rate and sweating. Albuterol administered at 2 μg/kg via inhalation may be useful for increasing PaO₂ in anesthetized horses.