Respiratory and metabolic effects of massive administration of isotonic saline solution in heaves-affected and control horses

Reasons for performing study: It has been suggested that rapid administration of isotonic saline solution relieves airway obstruction in heaves-affected horses, but the efficacy and tolerability of this treatment is poorly documented. Objectives: To determine the respiratory and metabolic effects of a rapid administration of isotonic saline solution in control horses and those with heaves. Methods: Thirty litres isotonic saline solution were administered i.v. to 5 control (Group C) and 9 heaves-affected horses (Group H). Pulmonary function testing and arterial blood gas analysis were performed prior to saline infusion, at 90 and 180 mins after starting the infusion, and 1, 3, 6 and 10 days later. PCV, plasma total solids, plasma electrolytes (Na+, Cl- and K+) and venous blood gas analysis were performed prior, during and after saline infusion. Results: Rapid saline administration was shown to have no beneficial effects on lung function during infusion in Group H. On the contrary, they had significantly increased pulmonary resistance (R-L) at 180 mins following the initiation of saline administration compared to baseline. In Group C, saline administration resulted in a significant increase in R-L at 180 mins and a significant decrease in PaO2 at 90 mins. These results suggest a transient decrement in lung function caused by rapid saline administration. Group H had a metabolic alkalosis with hypochloraemia at baseline compared to control horses. This resolved following i.v. saline administration and returned to baseline within 6 h after treatment had been discontinued. Conclusion: The administration of saline to Group H did not improve airway function significantly, but resulted in mild and transient side effects. Potential relevance: Rapid administration of isotonic saline alone is not an effective therapy for heaves in horses.