Effect of endotoxin administration on equine digital hemodynamics and starling forces.

The research article explores the effects of an endotoxin administration on the blood flow and capillary system within a horse’s foot, revealing significant changes in vascular resistance but no parallel changes to those observed in cases of experimentally induced laminitis.

Experiment Methodology

• The experiment involved testing a pump-perfused extracorporeal (outside the body) isolated digital (relating to the digit or foot of a horse) preparation. This was done to accurately assess the foot’s hemodynamics and microvascular function.
• Testing involved 30-minute infusions of either saline solution (as a control) or endotoxin, after which various measurements such as blood flow, arterial, venous, and capillary pressures were recorded every 15 minutes for a duration of 150 minutes.
• From the collected measurements, further calculations were made to determine total vascular resistance and pre- and postcapillary resistances.
• Following these measurements, isogravimetric capillary filtration coefficient, vascular compliance, and the osmotic reflection coefficient were noted down to look for any changes in these factors as a result of the infusions.

Results and Findings

• There were no observed changes in hemodynamic values for equine digits when control equine digits were used.
• However, in the 120 minutes after the infusion of endotoxin, digital blood flow decreased by 43%, and total vascular resistance increased by 89%. Precapillary resistance also saw a significant increase of 122%, while postcapillary resistance did not change significantly.
• No changes in the vascular compliance or the capillary filtration coefficient were observed in response to either treatment. Similarly, the osmotic reflection coefficient, an index of the permeability, didn’t differ significantly between the digits of the endotoxin-treated and control groups.

Conclusion

• The data collected suggested that the increase in vascular resistance during endotoxemia may be attributable to arterial/arteriolar constriction. It was also observed that the permeability nor the surface area of the exchange vasculature within the digit was not significantly affected by the endotoxin.
• While it was clear that marked alterations in vascular function were seen after the administration of endotoxin, these changes did not follow the same patterns documented in association with experimentally induced laminitis, hence suggesting that the effects of endotoxins may not be a primary cause of laminitis.