Haemodynamic, pathological, haematological and behavioural changes during endotoxin infusion in equine neonates.

This research studied the effects of artificially induced low-level endotoxemia (presence of endotoxins in the blood) in newborn horses. The endotoxins given were from the bacteria Salmonella typhimurium. They examined various clinical signs, blood properties, and blood flow parameters, noting several changes as a result of the endotoxin infusion, some of which returned to baseline suggesting the onset of tolerance.

Experiment Details

• The study involved four fresh, equine neonates aged between 2 to 5 days, who were administered an endotoxin, Salmonella typhimurium, intravenously over a 5-hour period. The dosage was 0.5 micrograms per kg body weight.
• As a control experiment, a 4-day-old and a 5-day-old foal were given a sterile isotonic saline solution in the same manner.

Monitoring and Observation

• Clinical signs and haematological (blood) as well as biochemical parameters were keenly monitored, blood samples were taken for evaluation.
• The parameters of the haemodynamics (the physics of blood flow in the circulatory system) were recorded every hour during and after (6 and 24 hours) the infusion.

Findings

• Foals given the endotoxin infusion exhibited depression, anorexia, increase in rectal temperature, variations in leucocyte count (first reduction, then increment), low blood sugar levels (hypoglycaemia), increase in prothrombin time (a measure of blood clotting ability), and increased pulmonary and systemic vascular resistance.
• Changes in pulmonary artery pressure, pulmonary artery wedge pressure, right atrial pressure and a minor decrease in blood oxygen levels were other common findings in the endotoxin-infused foals.
• Despite the fluctuations in these parameters during the infusion, the foals didn’t go into shock and they appeared healthy shortly after the discontinuation of the infusion.
• The return of certain parameters, such as body temperature, prothrombin time, and neutrophil count to baseline levels during endotoxin infusion in some foals could point to an induction of tolerance to the endotoxin.

Control Experiment Outcomes

• The control foals, which received the sterile solution, remained alert throughout the experiment, and parameters like body temperature, prothrombin time and fibrinogen stayed constant.
• Rise in blood sugar levels (hyperglycaemia), a fleeting rise in partial thromboplastin time (APTT) and some variation in hemodynamic parameters were noted during the infusion in the control foals.