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POTENTIAL BENEFIT FROM A H 1 ‐ RECEPTOR ANTAGONIST ON POSTEXERCISE SYNCOPE IN THE HEAT
Author(s) -
McCord Jennifer Lockwood,
Pellinger Thomas K,
Lynn Brenna M,
Halliwill John R
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.957.6
Subject(s) - supine position , medicine , orthostatic vital signs , antagonist , blood pressure , anesthesia , cardiology , blockade , receptor
H 1 ‐receptors mediate the first 30 minutes of postexercise hypotension. Immediately after exercise, syncope can occur due to an exaggerated form of postexercise hypotension. Therefore, we hypothesized that orthostatic hypotension occurring immediately after exercise would be attenuated with a H 1 ‐receptor antagonist. We studied 15 endurance exercise trained men and women in an environmental chamber set at 35 °C and 30% humidity. Subjects were studied in the supine position prior to a 45 minute bout of treadmill running at 50% of VO 2max . Immediately after exercise, measurements were taken in the supine position before the subjects were moved into a 60° head‐up tilt. Measurements included arterial pressure and brachial blood flow on a control and a H 1 ‐receptor antagonist (blockade) day. Mean arterial pressure was reduced 1 minute into the tilt compared to preexercise values on the control day (76.2 ± 0.5 vs 74.2 ± 0.5 mmHg; P < 0.05). This reduction was not seen on the blockade day (75.2 ± 0.3 vs 75.0 ± 0.5 mmHg; P > 0.41). There were no differences in brachial vascular conductance (calculated as flow/pressure) in response to the head‐up tilt between the study days (P > 0.23). When comparing the length of the head‐up tilt between study days, the blockade lengthened the mean tilt time by 94 seconds (P = 0.098). These data suggest that a H 1 ‐receptor antagonist could potentially benefit postexercise syncope in a hot environment.