Hypoperfusion of the small intestine during slow infusion of a low dosage of endotoxin in anesthetized horses.

This research investigates how a small dose of endotoxin (a toxic substance bound to bacterial cell walls and released when the bacteria rupture) affects blood flow and pressure in the intestines of anesthetized horses, comparing it to the effects of a sodium chloride solution. It concluded that endotoxins significantly constrict intestinal blood vessels, impacting the compensatory stages of endotoxemia (a condition where endotoxins are present in the blood).

Research Goals

The researchers seek to observe and measure the effects of intravenously infused endotoxin on the blood flow of the small intestine in horses. As a comparison, they used a 0.9% sodium chloride solution to determine the physiological impact of endotoxin.

Research Methodology

• The researchers chose 6 horses that were anesthetized for the study.
• They administered endotoxin intravenously for half an hour at a cumulative dosage of 0.03 micrograms/kg.
• Several metrics were monitored and compared to the effects seen when infusing a sodium chloride solution. These metrics included average arterial pressure, capillary pressure, venous pressure, total vascular resistance, precapillary resistance, postcapillary resistance, and the capillary filtration coefficient within the jejunum (the middle section of the small intestine).

Results

The research found that:

• Endotoxin significantly decreased the flow of blood in the intestinal veins of horses. This was due to the vasoconstrictive properties induced by the endotoxin, causing the blood vessels to narrow.
• Increased vascular resistance in the intestines was not due to changes in total resistance but was instead due to changes in precapillary resistance.
• The capillary filtration coefficient remained unchanged by endotoxin. This implies that the ability of fluid to permeate through the capillary walls remained unaffected by the presence of endotoxin.

Conclusions

The results suggested that endotoxemia, when present in the compensatory stages, leads to vasoconstriction (narrowing of blood vessels) in the intestines. The specific impact of this intestinal vasoconstriction remains to be further explored. This finding helps better understand the physiological response and adaptation during the stages of endotoxemia in horses and potentially other animals or humans.