Glucose and insulin dynamics associated with continuous infusion of dextrose or dextrose and insulin in healthy and endotoxin-exposed horses

The objective of the study was to investigate and characterize the effects of a continuous rate infusion of dextrose or dextrose and insulin on glucose and insulin dynamics in both healthy and endotoxin-exposed horses. Administration of a low dose of endotoxin has been used in horses to mimic the clinicopathologic changes seen in endotoxemia, including the development of an inflammatory response. Our hypothesis was that a continuous rate infusion of insulin at a rate of 0.07 IU/kg/hr would prevent the development of hyperglycemia induced by administration of dextrose in both healthy and endotoxin-exposed horses. Nine healthy adult horses were used in the study.

In Phase 1 of the experiment, horses received a saline infusion or a dextrose infusion in a balanced crossover design. In Phase 2 of the experiment, horses received a dextrose and insulin infusion, both prior to and after receiving a low dose of endotoxin (no LPS group and LPS group respectively) in a balanced crossover design. Blood samples were collected at regular intervals throughout both phases for measurement of plasma glucose and insulin concentrations.

Infusion of dextrose alone resulted in hyperglycemia for nearly the entire study period. Insulin concentration was also increased in comparison to the saline infusion. When comparing the dextrose treatment group to the combined dextrose and insulin treatment group (no LPS group), the insulin levels were significantly greater over time in the latter group and resulted in maintenance of euglycemia. When comparing the no LPS group to the LPS group, both the glucose and insulin concentrations were higher in the LPS group but euglycemia was still achieved. These results serve to validate the dose of insulin used in this study (0.07 IU/kg/hr) in regards to effective prevention of hyperglycemia when administered concurrently with a dextrose infusion. Hyperglycemia was prevented in both healthy and endotoxin-exposed horses. In addition, the dose of insulin used was demonstrated to be safe, as hypoglycemia did not occur in any of the horses.