Venoarterial PCO2 gradient does not correlate with cardiac output, base excess and arterial lactate concentration in septic shock patients
© BioMed Central Ltd. 2004
Published: 15 March 2004
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.
We retrieved 21 patients from our prospective collected data base from January to December 2000. APACHE II scores were calculated at admission and ΔPCO2, cardiac output, BE and LAC were recorded at the moment of pulmonary artery catheter insertion and 24 hours after. All four variables had a normal distribution in our sample. Correlation between ΔPCO2 and the other three variables was performed, using the Pearson coefficient.
The patients' age was 53.1 ± 13.9 years and the APACHE II score was 26.0 ± 7.4. ΔPCO2 was not correlated with any of the other three variables. The Pearson correlation coefficient was -0.173 (P = 0.29), 0.291 (P = 0.07) and 0.08 (P = 0.66) for cardiac output, BE and LAC, respectively.
ΔPCO2 is not correlated with cardiac output, BE and LAC in septic shock patients.