title: Normovolemia defined according to cardiac stroke volume in healthy supine humans.
abstract: BACKGROUND
  Both hypovolemia and a fluid overload are detrimental for outcome in surgical patients but the effort to establish normovolemia is hampered by the lack of an operational clinical definition. Manipulating the central blood volume on a tilt table demonstrates that the flat part of the Frank-Starling curve is reached when subjects are supine and that finding may be applicable for a clinical definition of normovolemia. However, it is unknown whether stroke volume (SV) responds to an increase in preload induced by fluid administration.
  
  
  METHODS
  In 20 healthy subjects (23 +/- 2 years, mean +/- SD), SV was measured by esophageal Doppler before and after fluid administration to evaluate whether SV increases in healthy, non-fasting, supine subjects. Two hundred millilitres of a synthetic colloid (hydroxyethyl starch, HES 130/0.4) was provided and repeated if a >or=10% increment in SV was obtained.
  
  
  RESULTS
  None of the subjects increased SV >or=10% following fluid administration but there was a minor increase in mean arterial pressure (92 +/- 15 to 93 +/- 12 mmHg, P = 0.01), while heart rate (HR) (66 +/- 12 beats min(-1); P = 0.32), cardiac output (4.8 +/- 1.1 l min(-1); P = 0.25) and the length of the systole corrected to a HR of 60 beats/min (corrected flow time; 344 +/- 24 ms; P = 0.31) did not change.
  
  
  CONCLUSIONS
  Supporting the proposed definition of normovolemia, non-fasting, supine, healthy subjects are provided with a preload to the heart that does not limit SV suggesting that the upper flat part of the Frank-Starling relationship is reached.
authors.affiliation: Department of Anesthesiology.|Section of Surgical Pathophysiology, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Bundgaard-Nielsen
authors.affiliation: Department of Anesthesiology.|Section of Surgical Pathophysiology, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Christoffer C
authors.initials: CC
authors.lastname: Jørgensen
authors.affiliation: Section of Surgical Pathophysiology, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Kehlet
authors.affiliation: Department of Anesthesiology.
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001794:Blood Pressure; D001810:Blood Volume / Q000187:drug effects; D003718:Denmark; D005260:Female; D006339:Heart Rate; D006801:Humans; D006895:Hydroxyethyl Starch Derivatives / Q000008:administration & dosage; D007262:Infusions, Intravenous; D008297:Male; D010952:Plasma Substitutes / Q000008:administration & dosage; D012016:Reference Values; D013318:Stroke Volume / Q000187:drug effects; D016683:Supine Position; D018667:Tilt-Table Test; D018608:Ultrasonography, Doppler; D055815:Young Adult
chemical_list: D006895:Hydroxyethyl Starch Derivatives; D010952:Plasma Substitutes