Fluid and electrolyte regulation in space.

Publisher Summary This chapter discusses the fluid and electrolyte regulation in space. During weightlessness, there is a fluid shift from the legs to the upper part of the body. The reduction of the total leg volume amounts to about 2 liters after 1 week of weightlessness. This shift occurs in both the intravascular and extravascular volumes. A reduction in the body fluid volume has been consistently demonstrated during both American and Soviet spaceflights. To gain further insight into fluid, electrolyte, and volume regulating hormone modifications induced by spaceflight, many investigators have used ground-based simulation of weightlessness by means of bed rest, head down tilt (HDT), immersion, or lower body positive pressure (antigravity suit). The chapter discusses that fluid and electrolyte regulation during spaceflight is at least a biphasic process, the first phase taking place during the first 24 hours in space and the second phase during the subsequent days.

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