Effects of Vasoconstrictors on Microcirculation

Abstract

Physiology and animal models often predict microvascular negative effects of excessive vasoconstric-tion. The following are among them: a drop in capillary pressure (even closure of capillaries), a drop in microvascular haematocrit, a possible drop in flow, a possible decrease in capillary density. In fact, the impact of usual vasoconstrictors is difficult to predict, e.g. norepinephrine is an alpha agonist, which simultaneously increases arteriolar but also venular resistances together with a possible increase in cardiac output by beta stimulation or thanks to preload effect. Concerning norepinephrine and probably terlipressin, the effects on splanchnic, renal and most often sublingual micro-circulation are globally either positive or neutral if a deep hypovolemia is treated before perfusion of the drug and if mean arterial pressure goal is below 75 mmHg. Phenylephrine seems deleterious and difficult to use. Vasopressin requires more studies concerning microcirculation. Careful titration and even decrementation of the drugs in case of tissue dysoxia (mottling of the skin, the increase of lactate levels) seems to be common sense.