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Norepinephrine release during orthostasis is similar in healthy individuals who are and are not susceptible to syncope
Author(s) -
Fu Qi,
Shibata Shigeki,
VanGundy Tiffany B,
Okazaki Kazunobu,
Levine Benjamin D
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.737.8
Subject(s) - presyncope , supine position , medicine , norepinephrine , fainting , blood pressure , heart rate , anesthesia , orthostatic vital signs , syncope (phonology) , tilt table test , cardiology , dopamine
Previous studies showed that individuals susceptible to syncope had low norepinephrine release during orthostasis. However under most circumstances, presyncopal subjects were returned to supine first, then blood samples were drawn, while blood was collected upright in those who didn't have presyncope. We tested the hypothesis that plasma norepinephrine is similar between individuals who are and aren't susceptible to syncope after returning to supine from upright. Muscle sympathetic nerve activity, blood pressure, and heart rate were recorded in 35 healthy young subjects who had no previous history of fainting, both supine and during 45‐min of 60° upright tilt. Blood samples were drawn supine, during tilt, and immediately after the subject was returned to supine either because they completed the prolonged tilt or developed presyncope. Fourteen had presyncope (fainters), while 21 completed the tilt (non‐fainters). There were no differences in any variable between fainters and non‐fainter supine and during acute tilt, though sympathetic withdrawal and a rapid decrease in blood pressure occurred at presyncope in all fainters. Plasma norepinephrine in the supine position ( P =0.222), after 5 ( P =0.234) and 20 min of tilt ( P =0.669), and after returning to supine ( P =0.305) were comparable between fainters and non‐fainters. These results suggest that norepinephrine release during orthostasis is similar between individuals who are and are not susceptible to syncope. The specific trigger precipitating syncope (sympathetic withdrawal in all fainters) remains unknown.