title: Aortic cross-clamping and reperfusion in pigs reduces microvascular oxygenation by altered systemic and regional blood flow distribution.
abstract: BACKGROUND
  In this study, we tested the hypothesis that aortic cross-clamping (ACC) and reperfusion cause distributive alterations of oxygenation and perfusion in the microcirculation of the gut and kidneys despite normal systemic hemodynamics and oxygenation.
  
  
  METHODS
  Fifteen anesthetized pigs were randomized between an ACC group (n = 10), undergoing 45 minutes of aortic clamping above the superior mesenteric artery, and a time-matched sham surgery control group (n = 5). Systemic, intestinal, and renal hemodynamics and oxygenation variables were monitored during 4 hours of reperfusion. Microvascular oxygen partial pressure (microPo(2)) was measured in the intestinal serosa and mucosa and the renal cortex, using the Pd-porphyrin phosphorescence technique. Intestinal luminal Pco(2) was determined by air tonometry and the serosal microvascular flow by orthogonal polarization spectral imaging.
  
  
  RESULTS
  Organ blood flow and renal and intestinal microPo(2) decreased significantly during ACC, whereas the intestinal oxygen extraction and Pco(2) gap increased. The intestinal response to reperfusion after ACC was a sustained reactive hyperemia but no such effect was seen in the kidney. Despite a sustained high intestinal O(2) delivery, serosal microPo(2) (median [range], 49 mm Hg [41-67 mm Hg] versus 37 mm Hg [27-41 mm Hg]; P < 0.05 baseline versus 4 hours reperfusion) and the absolute number of perfused microvessels decreased along with an increased intestinal Pco(2) gap (17 mm Hg [10-19 mm Hg] versus 23 mm Hg [19-30 mm Hg]; P < 0.05). In contrast, the kidney showed a progressive O(2) delivery decrease accompanied by a decrease in renal cortex oxygenation (70 mm Hg [52-93 mm Hg] versus 57 mm Hg [33-64 mm Hg]; P < 0.05).
  
  
  CONCLUSIONS
  Increased systemic and regional blood flow and oxygen supply after ACC does not ensure adequate regional blood flow and microcirculatory oxygenation in all organs.
authors.affiliation: Department Anaesthesia and Critical Care Medicine, University Hospital, University of Basel, Spitalstrasse 21, 4031 Basel, Switzerland. siegemundm@uhbs.c
authors.forename: Martin
authors.initials: M
authors.lastname: Siegemund
authors.forename: Jasper
authors.initials: J
authors.lastname: van Bommel
authors.forename: Michiel E
authors.initials: ME
authors.lastname: Stegenga
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Studer
authors.forename: Mat
authors.initials: M
authors.lastname: van Iterson
authors.forename: Sandra
authors.initials: S
authors.lastname: Annaheim
authors.forename: Alexandre
authors.initials: A
authors.lastname: Mebazaa
authors.forename: Can
authors.initials: C
authors.lastname: Ince
mesh_terms: D000818:Animals; D001011:Aorta / Q000601:surgery*; D002245:Carbon Dioxide / Q000097:blood; D003250:Constriction; D004195:Disease Models, Animal; D006940:Hyperemia / Q000097:blood / Q000503:physiopathology; D007082:Ileum / Q000098:blood supply*; D007668:Kidney / Q000098:blood supply*; D008297:Male; D008833:Microcirculation; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D012039:Regional Blood Flow; D012079:Renal Circulation; D015424:Reperfusion; D015427:Reperfusion Injury / Q000097:blood / Q000209:etiology / Q000503:physiopathology*; D013152:Splanchnic Circulation; D013552:Swine; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen