Thromboxane, prostaglandin I2 (epoprostenol), and the hemodynamic changes in equine endotoxin shock

This study had 2 objectives: (i) to correlate plasma thromboxane and prostaglandin I2 (epoprostenol) concentrations with hemodynamic changes occurring in equine endotoxin shock, and (ii) to determine the effects of flunixin meglumine on plasma concentrations of these prostaglandins relative to hemodynamic changes. Shock was induced in 2 groups, each of 4 anesthetized ponies, and in a 3rd group of 2 ponies. Group A ponies were given endotoxin only (and were not treated), and group B ponies were given endotoxin and then treated with flunixin meglumine. Group C ponies were treated with flunixin meglumine 5 minutes before they were fiven endotoxin. Arterial, pulmonary arterial, and central venous pressures were measured and blood samples were collected at 0, 0.1, 0.25, 0.5, 1, 1, 3, and 4 hours after ponies were given the endotoxin. The plasma thromboxane and prostaglandin I2 concentrations were increased in equine endotoxic shock. Increased thromboxane concentration was associated with the high pulmonary arterial and central venous pressures and low arterial blood pressure in the minutes immediately after the ponies were given endotoxin. The increased prostaglandin I2 concentration was associated with systemic hypotension at 1 to 2 hours after endotoxin. Treatment of ponies with flunixin meglumine after endotoxin was given (group B) prevented the prostaglandin I2 rise and the associated hypotension. Treatment with fluixin meglumine before endotoxin was given prevented the increase of the plasma thromboxane and prostaglandin I2 values, along with the associated hemodynamic changes.