Effects of high doses of insulin on systemic haemodynamics and regional blood flows in dogs

This study describes the effects of a wide range of plasma concentrations of insulin on systemic haemodynamics and free fatty acids (FFA) and the effect of a high dose of insulin on regional blood flows in the femoral, carotid, mesenteric and renal arteries. Insulin was infused in 10 dogs at rates of 4, 8, 16, 32, 64 and 128 IU/kg/h, and the experiments were concluded with a bolus injection of 300 IU. Plasma glucose concentrations were kept constant during the experiments. A dose-related increase in maximum rate of left ventricular pressure rise, stroke volume and cardiac output, and decrease in total peripheral resistance was found with insulin infusion rates up to 64 IU/kg/h. Heart rate and mean aortic blood-pressure were unchanged. The maximum antilipolytic effect was obtained at an infusion rate of 16 IU/kg/h. Insulin was given as a bolus dose of 300 IU in 6 dogs. Blood-flow was increased in all vascular beds, but insulin caused a redistribution of cardiac output. The greatest increases occurred in the femoral and carotid vascular beds, and the least occurred in the renal bed. Mesenteric blood-flow was increased in proportion to cardiac output. The results suggest that insulin exerts combined positive inotropic and vasodilating effects at high dose levels, which result in improved regional perfusion. It may be a potentially useful clinical agent with special benefit under circumstances where enhanced cerebral blood-flow is of importance.