RABBIT SKELETAL-MUSCLE PO2 DURING HYPODYNAMIC SEPSIS

We measured skeletal muscle tissue Po2 (PtO2) in anesthetized rabbits (n = 7) following infusion of an intravenous bolus of E coli endotoxin. An array of surface Po2 microelectrodes was placed over the hindlimb biceps femoris muscle and sufficient readings were obtained to construct a PtO5 histogram. Changes in the histogram standard deviation were used to characterize micro-circulatory maldistribution. Systemic O2 consumption (Vo2) was measured by the expired gas method. Cardiac output (Q) and systemic O2 transport (To2) were calculated. Samples of arterial, right atrial (ra), and hindlimb venous blood, from a catheter placed in the infrarenal portion of the vena cava, were simultaneously obtained for measurement of blood gases and saturations. Following the administration of endotoxin, there were decreases in Q and To2 of approximately 50 percent. The Vo2 initially decreased 23 percent, but returned to baseline levels 30 minutes after endotoxin administration. Systemic O2 extraction ratio (ERo2 = Vo2/To2) increased from 0.32 +/- .03 to 0.54 +/- .07 (p < 0.01), whereas hindlimb ERo2 increased from 0.42 +/- .03 to 0.60 +/- .02 (p < 0.01). The arithmetic mean of the PtO2 histograms decreased after endotoxin infusion (43 +/- 4 to 7 +/- 2 mm Hg; p < 0.01), but PLO2 remained at baseline levels (35 +/- 2 vs. 33 +/- 2 mm Hg; p = NS). The standard deviation of the PtO2 histograms remained constant during the experiment. This finding supports the notion that skeletal muscle microcirculatory heterogeneity does not increase during endotoxin induced hypodynamic sepsis.