title: The influence of vasovagal response on the coagulation system.
abstract: BACKGROUND
  Vasovagal response (VVR) is provoked by a reduced venous blood return to the heart as a reaction to orthostatic stress and to haemorrhage. Recently, two cases were reported showing elevated plasma concentration of von-Willebrand-factor (VWF) and factor VIII (FVIII) after VVR due to venapuncture. Although the effect of epinephrine as trigger for VWF liberation is known, a connection between VVR and activation of the coagulation system has not been studied systematically.
  
  
  METHODS
  We examined 21 subjects with lower body negative pressure. We measured the plasma concentration of von-Willebrand-factor-antigen (VWF:Ag), the activity of von-Willebrand-factor-Ristocetin-Cofactor (VWF:RiCo) and FVIII at several stress-levels and consecutively split up the different VWF-multimers.
  
  
  RESULTS
  In 16 of 21 subjects VVR could be induced. These subjects showed a significant increase of VWF:Ag concentration in plasma and an increase of FVIII and VWF:RiCo activity. The five individuals who experienced all stress-levels without VVR did not show any changes in their clotting factor levels.
  
  
  CONCLUSIONS
  VVR leads to measurable changes in the coagulation system. This might be a further diagnostic tool in treating patients with syncope.
authors.affiliation: Autonomic Laboratory, Department of Neurology, Alfried Krupp von Bohlen und Halbach Hospital, Alfried-Krupp-Strasse 21, 45117, Essen, Germany. markus.kraemer1977@gmx.de
authors.forename: Markus
authors.initials: M
authors.lastname: Kraemer
authors.forename: Markus
authors.initials: M
authors.lastname: Kuepper
authors.forename: Andrea
authors.initials: A
authors.lastname: Nebe-vom Stein
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sorgenfrei
authors.forename: Rolf R
authors.initials: RR
authors.lastname: Diehl
mesh_terms: D000293:Adolescent; D000328:Adult; D001777:Blood Coagulation / Q000502:physiology*; D005169:Factor VIII / Q000378:metabolism; D005260:Female; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D014630:Vagus Nerve / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult; D014841:von Willebrand Factor / Q000276:immunology / Q000378:metabolism
chemical_list: C029417:Von Willebrand antigen; D014841:von Willebrand Factor; D005169:Factor VIII