Endotoxemia decreases matching of regional blood flow and O2 delivery to O2 uptake in the porcine left ventricle

Abstract

Heterogeneity of regional coronary blood flow is caused in part by heterogeneity in O2 demand in the normal heart. We investigated whether myocardial O2 supply/demand mismatching is associated with the myocardial depression of sepsis. Regional blood flow (microspheres) and O2 uptake ([13C]acetate infusion and analysis of resultant NMR spectra) were measured in about nine contiguous tissue samples from the left ventricle (LV) in each heart. Endotoxemic pigs ( n = 9) showed hypotension at unchanged cardiac output with a fall in LV stroke work and first derivative of LV pressure relative to controls ( n = 4). Global coronary blood flow and O2 delivery were maintained. Lactate accumulated in arterial blood, but net lactate extraction across the coronary bed was unchanged during endotoxemia. When LV O2 uptake based on blood gas versus NMR data were compared, the correlation was 0.73 ( P = 0.007). While stable over time in controls, regional blood flows were strongly redistributed during endotoxin shock, with overall flow heterogeneity unchanged. A stronger redistribution of blood flow with endotoxin was associated with a larger fall in LV function parameters. Moreover, the correlation of regional O2 delivery to uptake fell from r = 0.73 ( P < 0.001) in control to r = 0.18 ( P = 0.25, P = 0.009 vs. control) in endotoxemic hearts. The results suggest a redistribution of LV regional coronary blood flow during endotoxin shock in pigs, with regional O2 delivery mismatched to O2 demand. Mismatching may underlie, at least in part, the myocardial depression of sepsis.