Sepsis depresses the metabolic oxygen reserve of the coronary circulation in mature sheep

This study was undertaken to describe the metabolic O-2 reserve of the coronary circulation in an awake sheep model of hyperdynamic sepsis. Forty-eight hours after sheep were randomized to either a SHAM group (n = 8) or a cecal ligation and perforation (CLP) group (n = 8), we measured hemodynamics, organ blood flows, and systemic and myocardial O-2 metabolism variables at baseline and through four stages of progressive hypoxia. A significant elevation in arterial lactate levels occurred at a higher O-2 delivery in the CLP group (527 +/- 55 ml/min/m(2)) than in the SHAM group (357 +/- 29 ml/min/m(2), p < 0.05). The heart's metabolic O-2 reserve (difference in circulatory determinants of O-2 availability between baseline and where O-2 uptake could not be sustained:) was exhausted at an O-2 content of 56.9 +/- 4.2 ml O-2/L in SHAM sheep and 79.6 +/- 7.2 ml O-2/L (p < 0.05) in CLP sheep. An increase in coronary blood flow was three times greater in SHAM than in CLP animals. Myocardial O-2 extraction increased with hypoxia in SHAM sheep (0.78 +/- 0.03 to 0.88 +/- 0.02, p < 0.05), but not in CLP sheep (0.79 +/- 0.02 to 0.80 +/- 0.04). We conclude that the metabolic O-2 reserve of the coronary circulation is depressed in this model of hyperdynamic sepsis as the ability to increase both coronary blood flows and myocardial O-2 extraction was significantly limited.