Metabolic acidosis in patients with severe sepsis and septic shock: A longitudinal quantitative study

TLDR

The study aimed to characterize the composition of metabolic acidosis in patients with severe sepsis or septic shock at ICU admission and over the first five days of stay. A prospective observational cohort of 60 patients in a 12‑bed ICU measured inorganic ion difference, lactate, albumin, phosphate, and strong ion gap daily for five days to quantify their contributions to acidosis. At admission survivors exhibited a milder base excess deficit mainly due to hyperchloremia, and their acidosis resolved over five days as lactate and strong ion gap decreased, whereas nonsurvivors remained acidotic; the initial inorganic ion difference independently predicted poorer outcomes.

Abstract

To describe the composition of metabolic acidosis in patients with severe sepsis and septic shock at intensive care unit admission and throughout the first 5 days of intensive care unit stay.Prospective, observational study.Twelve-bed intensive care unit.Sixty patients with either severe sepsis or septic shock.None.Data were collected until 5 days after intensive care unit admission. We studied the contribution of inorganic ion difference, lactate, albumin, phosphate, and strong ion gap to metabolic acidosis. At admission, standard base excess was -6.69 +/- 4.19 mEq/L in survivors vs. -11.63 +/- 4.87 mEq/L in nonsurvivors (p < .05); inorganic ion difference (mainly resulting from hyperchloremia) was responsible for a decrease in standard base excess by 5.64 +/- 4.96 mEq/L in survivors vs. 8.94 +/- 7.06 mEq/L in nonsurvivors (p < .05); strong ion gap was responsible for a decrease in standard base excess by 4.07 +/- 3.57 mEq/L in survivors vs. 4.92 +/- 5.55 mEq/L in nonsurvivors with a nonsignificant probability value; and lactate was responsible for a decrease in standard base excess to 1.34 +/- 2.07 mEq/L in survivors vs. 1.61 +/- 2.25 mEq/L in nonsurvivors with a nonsignificant probability value. Albumin had an important alkalinizing effect in both groups; phosphate had a minimal acid-base effect. Acidosis in survivors was corrected during the study period as a result of a decrease in lactate and strong ion gap levels, whereas nonsurvivors did not correct their metabolic acidosis. In addition to Acute Physiology and Chronic Health Evaluation II score and serum creatinine level,inorganic ion difference acidosis magnitude at intensive care unit admission was independently associated with a worse outcome.Patients with severe sepsis and septic shock exhibit a complex metabolic acidosis at intensive care unit admission, caused predominantly by hyperchloremic acidosis,which was more pronounced in nonsurvivors. Acidosis resolution in survivors was attributable to a decrease in strong ion gap and lactate levels.