||Quantitative relationships among plasma lactate, inorganic phosphorus, albumin, unmeasured anions and the anion gap in lactic acidosis
Figge, James ,
Bellomo, RinaldoEgi, Moritoki
110 , 2018-04 , Elsevier
Background: Quantitative relationships among plasma [Lactate], [Pi], [Albumin], unmeasured anions ([UA]) and the anion gap (AG(K)) in lactic acidosis (LA) are not well defined. Methods: Amathematical model featuring compensatory potassium and chloride shifts and respiratory changes in LA demonstrated: (1) AG(K) = [Lactate] + Zp x [Pi] + 2.4 x [Albumin] + constant1 + e, where Zp is a function of pH, and e reflects unmeasured anions and cations plus pH-related variations. Eq. (1) can be algebraically rearranged to incorporate the albumin-corrected anion gap, cAG(K): (2) cAG(K) = [Lactate] + Zp x [Pi] + constant2 + e. Eq. (1) was tested against 948 data sets from critically ill patients with [Lactate] 4.0 mEq/L or greater. AG(K) and cAG(K) were evaluated against 12,341 data sets for their ability to detect [Lactate] > 4.0 mEq/L. Results: Analysis of Eq. (1) revealed r(2) = 0.5950, p < 0.001. cAG(k) > 15mEq/L exhibited a sensitivity of 93.0% [95% CI: 91.3–94.5] in detecting [Lactate] > 4.0 mEq/L, whereas AG(K) > 15 mEq/L exhibited a sensitivity of only 70.4% [67.5–73.2]. Additionally, [Lactate] > 4.0 mEq/L and cAG(K) > 20 mEq/L were each strongly associated with intensive care unit mortality (χ(2) > 200, p < 0.0001 for each). Conclusions: In LA, cAG(K) is more sensitive than AG(K) in predicting [Lactate] > 4.0 mEq/L.