Condition of microcirculatory and hemostasis systems in rats after moderate hypothermia

Hypothermia produces a generalized impact on an organism, with involvement  of all organs and systems into the response. It was shown that hypothermia promotes multi-organ dysfunction syndrome, which makes it important to study the influence of hypothermia on condition of hemostasis and microcirculatory systems.

Aim. To study the condition of the hemostasis system and the microcirculatory bed in different periods of moderate hypothermia in rats.

Materials and Methods. The current study was performed on 50 male Wistar rats. Condition of microcirculatory blood stream in all animals was assessed with laser Doppler flowmetry. Condition of hemostasis system was studied according to routine protocols and an integrated method of examination – thromboelastography. Statistical analysis was performed using Statistica 6.0 software package (StatSoft, USA) with calculation of Mann-Whitney nonparametric test.

Results. Analysis of the experimental data showed that moderate hypothermia produced a pronounced modulating influence on the microcirculatory system. Vasodilatation occurred immediately after reaching the stage of hypothermia, suggesting the beginning of decompensation in the experimental animals. The highest risk for hemodynamic pathologies was observed 5 days after cessation of cooling and was characterized by a massive reduction in the vascular tone, intensification of hemodynamics against the background appearance of thrombinemia markers in the blood stream and pronounced inhibition of fibrinolysis. Enhanced hemodynamics of the nutritional vascular bed with the underlying progressive prothrombotic condition is a potent risk factor for thrombosis and multiple organ dysfunction syndrome. Vasospasm that developed 2 weeks after recovery of the body temperature, indicated a profound modulation of vasculature and preservation of high-level sympathetic input, as well as increasing rigidity of blood vessel walls. Rising fibrinogen concentrations confirm a progressive inflammatory reaction.

Conclusion. A moderate degree of hypothermia produces a pronounced modulating effect on the microcirculation. The established regularities make it possible to form a clear understanding of the course and development of the pathological reaction in the body of victims and to give recommendations on the use of pharmacological medicine for preventive therapy. Thus, a period has been established when thrombotic readiness is maximal, and use of anticoagulant and antiplatelet drugs is required, together with drugs that improve rheological properties of blood.