Gut and muscle tissue PO2 in endotoxemic dogs during shock and resuscitation

Abstract

There is indirect evidence that tissue hypoxia occurs in human sepsis and surface measures of muscle tissue PO2 (PtiO2) in hypodynamic endotoxic animals are decreased. This study assessed systemic and regional tissue oxygenation in a more relevant model of hyperdynamic endotoxicosis. We isolated venous outflow from the left hindlimb and a segment of ileum in six anesthetized dogs to measure muscle and gut O2 delivery and uptake (VO2) and lactate flux, gut intramucosal pH (pHi) by tonometry, and PtiO2 by multi-point surface electrodes placed on mucosal and serosal surfaces of gut and on muscle. We then infused Escherichia coli lipopolysaccharide (LPS; 2 mg/kg) over 1 h followed by a 2-h infusion of dextran (0.5 ml.kg-1.min-1). LPS infusion significantly decreased systemic and gut VO2, cardiac output (Q), and blood pressure and increased arterial lactate and gut lactate flux. Resuscitation increased Q to above baseline and restored systemic VO2. In response to LPS and then resuscitation, muscle PtiO2 distribution did not change, suggesting little microcirculatory disturbance, although mean PtiO2 first decreased and then increased. In contrast, gut VO2 and pHi remained low and lactate output remained high, despite restoration of gut blood flow. Gut VO2, lactate flux, pHi, and PtiO2 histograms were consistent with a marked redistribution of blood flow within the gut wall, away from the mucosa and toward the muscularis. These data show that, in hyperdynamic acute endotoxemia, skeletal muscle PtiO2 and VO2 are well maintained, but blood flow within the gut is significantly disturbed with mucosal hypoxia.