Rapid infusion of a phospholipid emulsion attenuates the effects of endotoxaemia in horses.

The research tested whether quickly administering a lower dose of phospholipid emulsions, which bind to endotoxins, could help combat endotoxaemia in horses, causing less haemolysis (destruction of red blood cells). The results showed that the emulsions noticeably reduced the damaging effects of endotoxaemia and caused a minimal degree of haemolysis, suggesting it could offer a new treatment method for endotoxaemia.

Objective and Methods

• The researchers aimed to determine whether rapidly administering a smaller overall dose of a phospholipid emulsion could lessen the effects of endotoxin (LPS), which causes endotoxaemia, and result in less haemolysis. They also aimed to test whether this emulsion could reduce the inflammatory effects of LPS in vitro (in a lab environment).
• To carry out this study, they gave twelve healthy horses either a saline solution or a phospholipid emulsion (100 mg/kg) via intravenous (i.v.) infusion. This was followed immediately by the administration of E. coli 055:B5 LPS (30 ng/kg).
• Various parameters were monitored before and at select times after the LPS was administered to track the effects of the emulsion. These included clinical parameters, haematological profiles, serum tumour necrosis factor (TNF) activity, serum lipid profiles, urine analyses and the severity of haemolysis.
• They also tested the effects of the emulsion on monocytes (a type of white blood cell) in vitro with LPS, after which they measured the TNF and tissue factor activities.

Results

• The tests revealed that clinical signs of endotoxaemia were reduced in horses that had been given the emulsion, including clinical score, heart rate, rectal temperature, serum TNF activity, and the leucopenic response (decrease in the number of white blood cells) to LPS.
• Three of the horses that got the emulsion had no haemolysis, two had mild haemolysis, and one had moderate haemolysis.
• There were no differences in the urinalysis results and creatinine concentrations over time or between the groups.
• Levels of phosphatidylcholine, bile acids, and triglycerides reached their peak right after the infusion. However, there were no significant changes in the concentrations of nonesterified fatty acids or cholesterol.
• When equine monocytes were incubated with the emulsion in vitro, the emulsion prevented LPS-induced TNF and tissue factor activities.

Conclusions

• The rapid administration of the phospholipid emulsion significantly reduced the inflammatory effects of LPS and only caused a small degree of haemolysis.
• The results of the in vitro tests suggest that the emulsion not only prevents the cytokine synthesis induced by LPS but also the expression of associated membrane mediators (i.e., tissue factor).
• The research concluded that rapid i.v. administration of emulsions containing phospholipids that bind endotoxin may provide a clinically useful method of treating endotoxaemia in horses.