INTERSTITIAL FLUID ACCUMULATION DOES NOT INFLUENCE OXYGEN-UPTAKE IN THE RABBIT SMALL-INTESTINE

Crystalloid resuscitation increases interstitial fluid volume. Intesti nal ischemia and impaired barrier function may contribute to the preci pitation of multiple organ failure. Accordingly, the intestine was cho sen as target organ to test whether interstitial oedema impairs oxygen extraction by the tissue. The portal vein in anaesthetized rabbits wa s partially obstructed for 30 min along with an intravenous infusion o f 0.9% saline 60-90 ml kg(-1) (oedema group, n=7). Total water content of the small intestine increased from 3.4 ml g(-1) dry weight in cont rol (n=8) to 3.9 ml g(-1) in the oedema group (P=0.049). Small intesti nal O-2 uptake was calculated from the arteriovenous O-2 content and e lectromagnetic flow measurements in the superior mesenteric artery. Me senteric how was reduced stepwise by a snare occluder around the arter y. intestinal oxygenation was monitored indirectly as well, by means o f mesenteric venous lactate, arterial base excess and by mucosal pH (p H(i)) assessed tonometrically. The oxygen extraction ratios were simil ar in the oedema and control group at similar oxygen supplies. After a 45 min flow reduction to 15% of baseline mesenteric venous lactate an d pH(i) did not differ between the groups. pH, averaged 7.31 and fell to 6.74. Below an intestinal OL uptake of 2.5 ml min(-1), pH(i) correl ated somewhat better with O-2 uptake (r=0.66) than did arterial base e xcess (r=0.50). The results indicate that acute elevation of extracell ular Volume to the extent in the present study, does not impede oxygen uptake in the gut.