title: Estimating unmeasured anions in critically ill patients: anion-gap, base-deficit, and strong-ion-gap.
abstract: We used 100 routine blood samples from critically ill patients to establish whether correcting the anion-gap and base-deficit for decreased plasma albumin improves agreement with the strong-ion-gap for estimating unmeasured anions and whether the modifications increase the proportion of samples with levels of anion-gap or base-deficit above the reference ranges. We used Bland-Altman analyses to compare the methods of estimating unmeasured ions. Compared with the strong-ion-gap, modification reduced the limits of agreement for both the anion-gap and the base-deficit. The bias for the base-deficit was also reduced but the bias for the anion-gap was increased. The proportion of samples with an anion-gap > 22 meq.l(-1) increased from 4 to 29% (p < 0.001), and the proportion with a base-deficit > 5 meq.l(-1) increased from 8 to 42% (p < 0.001). Consequently, metabolic acidosis from unmeasured ions in critically ill patients maybe more frequent than often recognised.
authors.affiliation: Department of Intensive are, Austin and Repatriation Medical Centre, Heidelberg, Victoria, Australia.
authors.forename: D A
authors.initials: DA
authors.lastname: Story
authors.forename: S
authors.initials: S
authors.lastname: Poustie
authors.forename: R
authors.initials: R
authors.lastname: Bellomo
mesh_terms: D000136:Acid-Base Equilibrium; D000137:Acid-Base Imbalance / Q000097:blood / Q000175:diagnosis*; D000138:Acidosis / Q000097:blood / Q000175:diagnosis; D002712:Chlorides / Q000097:blood; D016638:Critical Illness; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011446:Prospective Studies; D012709:Serum Albumin / Q000032:analysis; D012964:Sodium / Q000097:blood
chemical_list: D002712:Chlorides; D012709:Serum Albumin; D012964:Sodium