NASA Technical Reports Server (NTRS) : Midodrine pdf

NASA Technical Reports Server (NTRS) : Midodrine

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One possible mechanism for post-spaceflight orthostatic hypotension, which affects approximately 30% of astronauts after short duration shuttle missions, is inadequate norepinephrine release during upright posture. We performed a two phased study to determine the effectiveness of an alpha1-adrenergic agonist, midodrine, as a countermeasure to post-spaceflight orthostatic hypotension. The first phase of the study examined the landing day orthostatic responses of six veteran astronauts after oral midodrine (10 mg) administered on the ground within approximately two hours of wheel stop. One female crewmember exhibited orthostatic hypotension in a previous flight but not after midodrine. Five male crewmembers, who did not exhibit orthostatic hypotension during previous flights, also did not show signs of orthostatic hypotension after midodrine. Additionally, phase one showed that midodrine did not cause hypertension in these crewmembers. In the second phase of this study, midodrine is ingested inflight (near time of ignition, TIG) and orthostatic responses are determined immediately upon landing via an 80 degree head-up tilt test performed on the crew transport vehicle (CTV).

Four of ten crewmembers have completed phase two of this study. Two crewmembers completed the landing day tilt tests, while two tests were ended early due to presyncopal symptoms. All subjects had decreased landing day stroke volumes and increased heart rates compared to preflight. Midodrine appears to have increased total peripheral resistance in one crewmember who was able to complete the landing day tilt test. The effectiveness of midodrine as a countermeasure to immediate post-spaceflight orthostatic hypotension has yet to be determined; interpretation is made more difficult due to low subject number and the lack of control subjects on the CTV

• Creator/s: NASA Technical Reports Server (NTRS
• Date: 2/4/2008
• Year: 2008
• Book Topics/Themes: NASA Technical Reports Server (NTRS), COUNTERMEASURES, HYPOTENSION, NOREPINEPHRINE, ASTRONAUTS, PHARMACOLOGY, AEROSPACE MEDICINE, DRUGS, HYPERTENSION, SPACE FLIGHT, Stenger, Michael B., Stein, Sydney P., Meck, Janice V., Platts, Steven H

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