Orthostatic tolerance after space flight and model experiments: new approaches to evaluation and prevention
- V. B. Noskov
- Human Physiology
The effect of a diuretic on the ultrasound pattern of venous congestion in abdominal organs in a healthy subject staying in an antiorthostatic position (AOP, 15°) for 12 h was studied. After furosemide administration, the circulating plasma volume (CPV), total water content of the body, and extracellular fluid volume decreased more than without the treatment. Overall hypohydration of the body prevented the dilation of hepatic veins typical of an AOP while not affecting noticeably the venous congestion in the portal vein system. In addition, the administration of the diuretic prevented the activation of bile secretion and an increased gastric juice secretion under antiorthostatic conditions. Thus, it was demonstrated that pharmacological hypohydration, by decreasing the CPV and the blood pressure in the inferior vena cava, unloads hepatic veins and prevents enhanced secretion in organs of the digestive system under the conditions of gravitational redistribution of body fluids.