Rapid intravenous administration of isotonic saline solution does not relieve airway obstruction in heaves-affected horses, says Daniel Jean, MedVet, MS, PhD, Dipl. ACVIM, professor of clinical sciences at the University of Montreal.

“Massive administration of large volumes of saline has been recommended to achieve thinning of secretions and improve expectoration,” says Jean. Horses with heaves have more respiratory secretions than normal horses, and researchers on a study published in the Equine Veterinary Journal thought a large volume of saline could increase the pressure of blood vessels in the lungs, increase liquid in the bronchus, and help eject secretions out of the respiratory tract.

The 0.9% NaCl isotonic saline solution used in the study is the same solution used for fluid therapy in horses, humans, and other species, says Jean.

Fourteen adult horses were used in the study. Nine had been diagnosed with heaves, while the other five were considered free of respiratory disease. Over three hours, 30 liters of isotonic saline solution were given to each horse through catheters placed in their left and right jugular veins. “All horses demonstrated bilateral serous nasal discharge during the infusion,” says Jean. The horses also showed increased restlessness, wheezes in the trachea (seven of the nine horses with heaves, and two of the five healthy horses). Study horses also showed cough, anxiety, muscle tremors, decreased gut sounds, and tachycardia (rapid heart rate)