Aortic cross-clamping and reperfusion in pigs reduces microvascular oxygenation by altered systemic and regional blood flow distribution.
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.
Siegemund
Martin
M
Department Anaesthesia and Critical Care Medicine, University Hospital, University of Basel, Spitalstrasse 21, 4031 Basel, Switzerland. siegemundm@uhbs.c
van Bommel
Jasper
J
Stegenga
Michiel E
ME
Studer
Wolfgang
W
van Iterson
Mat
M
Annaheim
Sandra
S
Mebazaa
Alexandre
A
Ince
Can
C
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
D002245:Carbon Dioxide; D010100:Oxygen