title: The immediate and sustained effects of volume challenge on regional blood flows in pigs.
abstract: BACKGROUND
  The postoperative assessment of volume status is not straightforward because of concomitant changes in intravascular volume and vascular tone. Hypovolemia and blood flow redistribution may compromise the perfusion of the intraabdominal organs. We investigated the effects of a volume challenge in different intra- and extraabdominal vascular beds.
  
  
  METHODS
  Twelve pigs were studied 6 h after major intraabdominal surgery under general anesthesia when clinically normovolemic. Volume challenges consisted of 200 mL rapidly infused 6% hydroxyethyl starch. Systemic (continuous thermodilution) and regional (ultrasound Doppler) flows in carotid, renal, celiac trunk, hepatic, and superior mesenteric arteries and the portal vein were continuously measured. The acute and sustained effects of the challenge were compared with baseline.
  
  
  RESULTS
  Volume challenge produced a sustained increase of 22% +/- 15% in cardiac output (P < 0.001). Blood flow increased by 10% +/- 9% in the renal artery, by 22% +/- 15% in the carotid artery, by 26% +/- 15% in the superior mesenteric artery, and by 31% +/- 20% in the portal vein (all P < 0.001). Blood flow increases in the celiac trunk (8% +/- 13%) and the hepatic artery (7% +/- 19%) were not significant. Increases in regional blood flow occurred early and were sustained. Mean arterial and central venous blood pressures increased early and decreased later (all P < 0.05).
  
  
  CONCLUSIONS
  A volume challenge in clinically euvolemic postoperative animals was associated with a sustained increase in blood flow to all vascular beds, although the increase in the celiac trunk and the hepatic artery was very modest and did not reach statistical significance. Whether improved postoperative organ perfusion is accompanied by a lower complication rate should be evaluated in further studies.
authors.affiliation: Department of Anesthesiology, University Hospital Bern, Inselspital, CH-3010 Bern, Switzerland.
authors.forename: Syed Z
authors.initials: SZ
authors.lastname: Ali
authors.forename: Hendrik
authors.initials: H
authors.lastname: Bracht
authors.forename: Vladimir
authors.initials: V
authors.lastname: Krejci
authors.forename: Mario
authors.initials: M
authors.lastname: Beck
authors.forename: Michael
authors.initials: M
authors.lastname: Stalder
authors.forename: Luzius
authors.initials: L
authors.lastname: Hiltebrand
authors.forename: Jukka
authors.initials: J
authors.lastname: Takala
authors.forename: Sebastian
authors.initials: S
authors.lastname: Brandt
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D001810:Blood Volume / Q000502:physiology*; D005260:Female; D020896:Hypovolemia / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D019990:Perioperative Care / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology*; D013552:Swine; D014655:Vascular Resistance / Q000502:physiology