Effects of magnesium sulfate infusion on clinical signs and lung function of horses with severe asthma
Résumé
Abstract OBJECTIVE To evaluate whether MgSO 4 solution administered IV would improve the clinical signs and lung function of horses with severe asthma and potentiate the effects of salbutamol inhalation in those horses. ANIMALS 6 adult horses with severe asthma. PROCEDURES Asthmatic horses were used in 3 crossover design experiments (6 treatments/horse). Clinical scores for nasal flaring and the abdominal component associated with breathing and lung function were determined before and after administration of salbutamol (800 μg, by inhalation), MgSO 4 solution (2.2 mg/kg/min, IV, over 20 minutes), and combined MgSO 4 -salbutamol treatment. The data were collected during experimental procedures to assess salbutamol inhalation versus mock inhalation, MgSO 4 infusion versus infusion of saline (NaCl) solution (adjusted to the same osmolarity as the MgSO 4 solution), and the combined MgSO 4 -salbutamol treatment versus salbutamol inhalation alone. RESULTS Infusion of MgSO 4 significantly improved clinical scores when administered alone or in combination with salbutamol inhalation. With the combination treatment, lung function improved, albeit not significantly. Tidal volume also increased following combined MgSO 4 -salbutamol treatment. Salbutamol alone significantly improved lung function, whereas saline solution administration and a mock inhalation procedure had no effect on the studied variables. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that MgSO 4 infusion alone or in combination with salbutamol inhalation improved the clinical signs of severely asthmatic horses. The effects of MgSO 4 were not associated with significant lung function improvement, which suggested that the changes observed were attributable to alterations in the horses' breathing patterns. Infusion of MgSO 4 solution at the studied dose offers little advantage over currently used medications for the treatment of severe equine asthma.