title: Alcohol potentiates orthostatic hypotension : implications for alcohol-related syncope.
abstract: BACKGROUND
  Alcohol consumption may be linked to syncopal events. The mechanisms by which alcohol may induce syncope are unknown. Impairment of the response to orthostatic stress may be involved. Using a double-blind, randomized, placebo-controlled study, we tested the hypothesis that short-term alcohol intake causes orthostatic hypotension because of an impairment in the vasoconstrictor response to orthostatic stress.
  
  
  RESULTS
  We examined the effects of alcohol on blood pressure, heart rate, and forearm vascular resistance (FVR) during orthostatic stress achieved by stepwise increases in lower-body negative pressure (LBNP) in 14 healthy young volunteers. During the placebo session, blood pressure did not change significantly during LBNP at -5, -10, and -20 mm Hg. A significant decrease in blood pressure was evident only at -40 mm Hg. In contrast, blood pressure fell significantly at all levels of LBNP during the alcohol session. Compared with placebo, alcohol potentiated the hypotensive responses to LBNP, particularly at -40 mm Hg, when the decrease in systolic blood pressure after alcohol intake (-14 mm Hg) was double that after placebo intake (-7 mm Hg). FVR increased with LBNP after placebo. However, after alcohol intake, FVR did not increase during LBNP despite the potentiated decrease in blood pressure. FVR responses during LBNP were reduced during alcohol compared with placebo consumption (P=0.04).
  
  
  CONCLUSIONS
  Short-term alcohol consumption elicits hypotension during orthostatic stress because of impairment of vasoconstriction. These findings have implications for the understanding of the hemodynamic effects of alcohol and, in particular, for understanding syncopal events that occur in association with alcohol intake.
authors.affiliation: Cardiovascular Division, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa, USA.
authors.forename: K
authors.initials: K
authors.lastname: Narkiewicz
authors.forename: R L
authors.initials: RL
authors.lastname: Cooley
authors.forename: V K
authors.initials: VK
authors.lastname: Somers
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000503:physiopathology*; D001794:Blood Pressure; D003971:Diastole; D004311:Double-Blind Method; D000431:Ethanol / Q000097:blood; D005260:Female; D005542:Forearm / Q000098:blood supply; D006339:Heart Rate; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D008150:Lower Body Negative Pressure; D008297:Male; D012016:Reference Values; D013575:Syncope / Q000209:etiology / Q000503:physiopathology*; D013599:Systole; D014655:Vascular Resistance
chemical_list: D000431:Ethanol