Partitioning evolutive standard base excess determinants in septic shock patients.

BACKGROUND AND OBJECTIVES The amount of metabolic acidosis measured through the standard base excess (SBE) has been shown to be an outcome marker and its improvement has been associated with better survival. We studied the mechanism of standard base excess variation in the first three days of intensive care unit (ICU) stay through the evaluation of independent variables of physico-chemical approach. METHODS Data were retrieved from our prospective collected data base from patients with diagnosis of septic shock, daily up to the third day after the ICU admission. Single correlations between SBE and independent variables were performed as well as a mathematical multilinear model was built to disclose the SBE variation determinants. RESULTS We have shown that in septic shock patients the standard base excess variation during the first three days of ICU stay is weakly correlated to strong ion gap (SIG), lactate, creatinin and PaCO2 when individually analyzed. Analyzing concomitantly those independent variables, we built a mathematical model with a stepwise multilinear regression composed by apparent strong ion difference (SIDa), SIG, PaCO2, albumin and diuresis that resulted in a R² coefficient of 0.866 to determine SBE variation. CONCLUSIONS Variations of metabolic acidosis measured through the standard base excess in septic shock patients when analyzed until the third day after intensive care unit admission, is resultant of interaction of several independent determinants as PaCO2, diuresis, SIG, SIDa and albumin.