Midodrine as a Countermeasure for Post-spaceflight Orthostatic HypotensionUp to 30 % of astronauts exhibit post-spaceflight orthostatic hypotension due to inadequate norepinephrine release during upright posture following short duration spaceflight. We hypothesize that the (alpha)1-adrenergic agonist midodrine will be an effective countermeasure. This study is being conducted in 2 phases. The first phase is complete and consisted testing six short duration crew members. All of these subjects participated in preflight and postflight tilt testing on a control flight as well as on the test flights, where midodrine was administered after landing, 1 hour before testing. Hemodynamic variables were compared between the 2 flights. Midodrine improved stroke volume, cardiac output, systolic pressure and heart rate, without increasing vascular resistance. None of these subjects experienced orthostatic hypotension on landing day. Phase II is similar to phase I, except that midodrine is ingested in flight (near TIG) and the tilt test is performed immediately after landing on the CTV. One crewmember has completed phase II testing. This crewmember had no evidence of orthostatic hypotension or presyncope, four additional crewmembers have volunteered for this study. To date, midodrine has been shown to be a safe and effective countermeasure to post-spaceflight orthostatic hypotension.
Document ID
20070006523
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Platts, Steven H. (NASA Johnson Space Center Houston, TX, United States)
Ziegler, Michael G. (California Univ. San Diego, CA, United States)
Waters, Wendy W. (Wyle Labs., Inc. Houston, TX, United States)
Meck, Janice V. (NASA Johnson Space Center Houston, TX, United States)