INFLUENCE OF 21-DAY OF HEAD-DOWN BED REST ON THE HEMOSTASIS SYSTEM OF A HEALTHY HUMAN

The bed rest experiment involved 6 healthy men aged 24 to 41 years. The subjects were in the supine position for 21 days, the angle of inclination in the cranial direction was -6°. In citrated blood plasma on days 2, 5, 8 and 21 of exposure, as well as 7 days after its end, the following hemostasis parameters were determined: thrombin time, prothrombin time, activated partial thromboplastin time, fibrinogen and D-dimer concentrations, as well as activity of protein C. In comparison with background, there was slight elongation in prothrombin time on the 2nd and 5th days of the experiment, as well as on the 7th day of the recovery period, a slight shortening of the thrombin time on the 8th and 21st days of the experiment and on the 7th day of the recovery period, moderately elongated activated partial thromboplastine time on 5th and 21st day. The concentration of D-dimer was significantly reduced relative to the background in all periods of the survey, except for the 21st day, approaching the background values on the 7th day after the end of exposure. The activity of protein C did not change significantly during the entire experiment and was significantly lower than the background values only on the 7th day after the end of the experiment. The concentration of fibrinogen did not change significantly during all periods of the examination. The results of the study indicate minor changes in the parameters of the plasma component of the hemostatic system, indicating a decrease in procoagulant potential in the early stages of exposure and its increase in the later stages of hypokinesia and in the recovery period.