Venoarterial PCO2 gradient does not correlate with cardiac output, base excess and arterial lactate concentration in septic shock patients

According to modified Fick equation, the venoarterial PCO2 gradient (ΔPCO2) is inversely correlated to cardiac output so that an increase in the ΔPCO2 value can alert to the presence of low-flow states or at least to a mismatch between tissue blood flow and metabolism. In septic shock patients, however, the relation between cardiacoutput and ΔPCO2 is quite complex due to possible distributive abnormalities of macrocirculatory and microcirculatory blood flow. The objectives of this study was to determine whether there is a good correlation between cardiac output and ΔPCO2 in a group of septic shock patients and between ΔPCO2 base excess (BE) and arterial lactate concentration (LAC), these two latter already demonstrated as good predictors of mortality in critically ill patients.