Waters et al identified a number of risk factors for postspaceflight orthostatic hypotension. These can help to identify a patient who may develop problems with orthostatic hypotension upon return to Earth. The authors are from Baylor College of Medicine, University of California San Diego, and NASA Johnson Space Center in Houston.
Duration of spaceflights: 5 to 15 days
Postspaceflight orthostatic hypotension involves presyncope or syncope with one or more of the following:
(1) lightheadedness
(2) loss of peripheral vision
(3) sudden drop in systolic blood pressure < 70 mm Hg
It is seen in about 20% of astronauts and is associated with an inadequate cardiovascular response to an orthostatic challenge (such as trying to stand for 10 minutes).
Risk factors for postspaceflight orthostatic hypotension include:
(1) female gender
(2) low vascular resistance (associated with a low mean arterial pressure while standing)
(3) greater loss of plasma volume during the spaceflight (20% loss in patients with orthostatic hypotension vs 7% loss in those without orthostatic hypotension)
(4) a hypoadrenergic response to the orthostatic challenge (with small increase in norepinephrine)
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