ORTHOSTATIC HYPOTENSION IN PATIENTS, BED REST SUBJECTS, AND ASTRONAUTS

Orthostatic hypotension after even short space flights has affected a significant number of astronauts. Given the need for astronauts to fun ction at a high level of efficiency during and after their return from space, the application of pharmacologic and other treatments is stron gly indicated. This report addresses the clinical problem of orthostat ic hypotension and its treatments to ascertain whether pharmacologic o r physiologic treatment may be useful in the prevention of orthostatic hypotension associated with space flight. Treatment of orthostatic hy potension in patients now includes increasing intravascular volume wit h high sodium intake and mineralocorticoids, or increasing vascular re sistance through the use of drugs to stimulate alpha or block beta vas cular receptors. Earlier treatment used oral sympathomimetic ephedrine hydrochloride alone or with ''head-up'' bed rest.(1) Then long-acting adrenocortical steroid desoxycorticosterone preparations with high-sa lt diets were used to expand volume. Fludrocortisone was shown to prev ent the orthostatic drop in blood pressure.(2) The combination of the sympathomimetic amine hydroxyamphetamine and a monoamine oxidase inhib itor tranylcypromine(3) has been used, as has indomethacin alone.(4) D avies et al.(5) used mineralocorticoids at low doses concomitantly wit h alpha-agonists to increase vasocontrictor action. Schirger et al(6) used tranylcypromine and methylphenidate with or without a Jobst elast ic leotard garment or the alpha-adrenergic agonist midodrine (which st imulates both arterial and venous systems without direct central nervo us system or cardiac effects). Vernikos et al(7) established that the combination of fludrocortisone, dextroamphetamine, and atropine exhibi ted a beneficial effect on orthostatic hypotension induced by 7-day 6 degrees head-down bed rest (a model used to simulate the weightlessnes s of space Fight), Thus, there are numerous drugs that, in combination with mechanical techniques, including lower body negative pressure to elevate transmural pressure, could be studied to treat orthostatic hy potension after space flight.