Fludrocortisone does not prevent orthostatic hypotension in astronauts after spaceflight.

Abstract

BACKGROUND:

During stand/tilt tests after spaceflight, 20% of astronauts experience orthostatic hypotension and presyncope. Spaceflight-induced hypovolemia is a contributing factor. Fludrocortisone, a synthetic mineralocorticoid, has been shown to increase plasma volume and orthostatic tolerance in Earth-bound patients. The efficacy of fludrocortisone as a treatment for postflight hypovolemia and orthostatic hypotension in astronauts has not been studied. Our purpose was to test the hypothesis that astronauts who ingest fludrocortisone prior to landing would have less loss of plasma volume and greater orthostatic tolerance than astronauts who do not ingest fludrocortisone.

METHODS:

There were 25 male astronauts who were randomized into 2 groups: placebo (n = 18) and fludrocortisone (n = 7), and participated in stand tests 10 d before launch and 2-4 h after landing. Subjects took either 0.3 mg fludrocortisone or placebo orally 7 h prior to landing. Supine plasma and red cell volumes, supine and standing HR, arterial pressure, aortic outflow, and plasma norepinephrine and epinephrine were measured.

RESULTS:

On landing day, 2 of 18 in the placebo group and 1 of 7 in the fludrocortisone group became presyncopal (chi2 = 0.015, p = 0.90). Plasma volumes were significantly decreased after flight in the placebo group, but not in the fludrocortisone group. During postflight stand tests, standing plasma norepinephrine was significantly less in the fludrocortisone group compared with the placebo group.

CONCLUSIONS:

Treatment with a single dose of fludrocortisone results in protection of plasma volume but no protection of orthostatic tolerance. Fludrocortisone is not recommended as a countermeasure for spaceflight-induced orthostatic intolerance.

• Authors: Shang-Jin Shi, Donna A South, Janice V Meck
• Journal: Aviation, space, and environmental medicine (Aviat Space Environ Med) Vol. 75 Issue 3 Pg. 235-9 (Mar 2004) ISSN: 0095-6562 [Print] United States
• PMID: 15018291 (Publication Type: Clinical Trial, Journal Article, Randomized Controlled Trial, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Anti-Inflammatory Agents
• Fludrocortisone

Topics

• Adult
• Analysis of Variance
• Anti-Inflammatory Agents (therapeutic use)
• Astronauts
• Fludrocortisone (therapeutic use)
• Hemodynamics (drug effects, physiology)
• Humans
• Hypotension, Orthostatic (prevention & control)
• Hypovolemia (prevention & control)
• Male
• Space Flight
• Sympathetic Nervous System (physiology)
• Syncope (prevention & control)