Effect of hypertonic vs isotonic saline solution on responses to sublethal Escherichia coli endotoxemia in horses.

This study looks at the effect of different saline solutions on the cardiovascular responses of horses after being administered sublethal dosages of Escherichia coli endotoxin.

Overview of the Research

In this experiment, a specific dosage of Escherichia coli endotoxin (50 micrograms/ml mixed with lactated Ringer solution) was given to five horses until their pulmonary arterial pressure increased by 10 mm of Hg. This procedure was performed twice on each horse. They then underwent a two-period crossover trial in which the horses were given either hypertonic (2,400 mosm/kg of body weight) or isotonic (300 mosm/kg) NaCl solution intravenously after being exposed to the endotoxins.

Methodology

• Both hypertonic and isotonic solutions were administered at a dose of 5 ml/kg with an infusion rate of 80 ml/min.
• At different intervals (starting at the baseline before the endotoxin and salt solution were administered, and then every quarter to half an hour up to 4.5 hours), data set was collected. This includes variables such as mean arterial, central venous, and pulmonary arterial pressures, cardiac output, total peripheral vascular resistance, heart rate, and concentrations of Na, K, Cl, and total protein in the plasma.
• The cardiovascular variables were evaluated separately at 0.75 hour and the blood constituents were measured alone at 0.5 hour.
• After the endotoxin infusion was finished at the 0.25 hour mark, the saline infusion started, and was then completed by the 0.75 hour mark.

Results

• Before any fluids were administered and by 0.25 hour from the start of the endotoxin infusion, the cardiac output of the horses decreased while total peripheral resistance and pulmonary arterial pressure increased in both trials.
• When it came to the hypertonic saline trial for the rest of the protocol, cardiac output increased and total peripheral resistance decreased when compared to the corresponding values in the isotonic saline trial.

This research indicates that the type of saline solution administered post endotoxin exposure can have significant effects on a horse’s cardiovascular responses, with hypertonic solutions leading to different outcomes than isotonic ones.