Anion Gap, Anion Gap Corrected for Albumin, and Base Deficit Fail to Accurately Diagnose Clinically Significant Hyperlactatemia in Critically Ill Patients

Abstract

Anion gap, anion gap corrected for serum albumin, and base deficit are often used as surrogates for measuring serum lactate. None of these surrogates is postulated to predict hyperlactatemia in the critically ill. We prospectively collected data from September 2004 through August 2005 for 1381 consecutive admissions. Patients with renal disease, ketoacidosis, or toxic ingestion were excluded. Anion gap, anion gap corrected for albumin, and base deficit were calculated for all patients. We identified 286 patients who met our inclusion or exclusion criteria. The receiver-operating characteristic area under the curve for the prediction of hyperlactatemia for anion gap, anion gap corrected for albumin, and base deficit were 0.55, 0.57, and 0.64, respectively. Anion gap, anion gap corrected for albumin, and base deficit do not predict the presence or absence of clinically significant hyperlactatemia. Serum lactate should be measured in all critically ill adults in whom hypoperfusion is suspected.

A Fatal Case of Metformin-associated Lactic Acidosis

“…Therefore, when a patient who takes metformin shows abnormal vital signs, metformin-associated lactic acidosis should be considered as a differential diagnosis, especially when there is unexplained metabolic acidosis. The presence of an anion gap does not predict clinically significant hyperlactatemia, so all patients with unexplained metabolic acidosis should have their serum lactate level measured (5,6). By monitoring the serum metformin level during our patient's clinical course, we found that hemodiafiltration was useful in decreasing the serum metformin level.…”

The Serum Anion Gap in the Evaluation of Acid-Base Disorders

“…Only 44% of 47 patients with serum lactate .2.5 mmol/L had an elevated anion gap (27). Correction of the anion gap for serum albumin improved the sensitivity of the anion gap in detecting mild hyperlactatemia to 75% (28) in one and 94% in the other (29).…”

Base excess

“…25 Another study showed no correlation among lactate, BE, anion gap, and anion gap corrected for albumin. 26 Therefore, anion gap fails as a single value because it cannot be interpreted without the knowledge of bicarbonate, pH, and PCO 2 .…”