["Small volume resuscitation" in hypovolemic rats. Effects on microcirculation].

Background: Numerous publications have analysed the hemodynamic effects of "small volume resuscitation" during the initial phases of hemorrhagic shock. Nevertheless nowadays the information about microcirculatory effects are poor. The aim of this study was to estimate the change of tissue perfusion in hypovolemic rats, before and after infusion of Ringer's lactate (RL), hypertonic saline solution (HS) or blood.
Methods: Mesocecal microcirculation was visualized by intravital microscopy during 30 minutes of hemorrhagic hypovolemia (MAP, mean arterial pressure of 40 mmHg) and subsequent reinfusion period. Rats were resuscitated with RL (shed volume), HS (one-seventh of the shed volume), or blood (shed volume). The perfusion was estimated through speed of red blood cells. Moreover MAP, pH and B.E. was measured.
Results: Thirty minutes after hemorrhage a very important decrease of capillary flow was noticed and in lesser quantity, of the flow in arterioles and venules. The RL infusion did not cause measureable changes of microcirculatory blood flows. The HS infusion caused an improvement in the flow of arterioles and venules but not in capillaries. The blood infusion caused a progressive improvement in the flow of arterioles, venules and capillaries, however at slightly lower values than previous hemorrhage.
Conclusions: Neither RL nor HS seem as efficient as blood to restore the microcirculatory blood flow in the mesocecum of the rats submitted to hemorrhagic hypovolemia.