Accidental hypothermia as a factor of microcirculatory disorders

Aim. To study the dynamics of indicators of microcirculation during a single episode of hypothermia of moderate degree in rats, both immediately after cessation of cooling, and in different periods of posthypothermia. Methods. The study was performed on 25 Wistar rats. The animals were subjected to a single immersion cooling in water at a temperature of 5 °C until reaching a rectal temperature of 27-30 °C. Analysis of the microvasculature was carried out immediately upon reaching a moderate degree of hypothermia, 2, 5, 10 and 14 days after the cooling. The microcirculation parameters were estimated using a laser analyzer of capillary circulation LAKK-02 (SMO «Lazma», Russia) at a wavelength of 0.63 μm. The main parameters of microcirculation were recorded, and the amplitude-frequency spectrum of blood flow oscillations was analyzed. Results. Immediately after reaching a moderate degree of hypothermia, vasospasm was recorded, which was confirmed by a decrease in the rate of perfusion and wave amplitudes of all frequency ranges. 2 days after stopping the cooling perfusion index returned to baseline, a decrease in amplitude of endothelial, vasomotor and respiratory waves was observed with an increase in pulse waves. On day 5, perfusion increased by 5 times was observed along with decreased amplitudes of the waves of all ranges. By day 10, the level of blood flow returned to its original values, and the wave amplitudes of all frequency ranges remained at the same low level. By day 14, a progressive decrease of the factors of bloodflow modulation was associated by the decrease of perfusion. Conclusion. Single cooling to a moderate degree of hypothermia leads to a progressive decrease of tissue perfusion and deep inhibition of active and passive factors of bloodflow modulation.