Bedside detection of urine β-hydroxybutyrate in diagnosing metabolic acidosis

Abstract

Objectives: While critically important, the rapid identification of the etiology of metabolic acidosis (MA) may be labor-intensive and time-consuming. Alcoholic, starvation, and severe diabetic ketoacidosis (AKA, SKA, and DKA, respectively) may produce β-hydroxybutyrate (BOHB) in marked excess of acetone (ACET) and acetoacetate (AcAc). Unfortunately, current urine dipstick technology poorly detects ACET and cannot measure BOHB. The inability to detect BOHB might delay therapy for ketoacidoses or provoke unnecessary evaluation or empiric treatment of other causes of MA, such as toxic alcohol poisoning. The authors tested the previous assertion that commonly available hydrogen peroxide (H2O2) would improve BOHB detection. The effectiveness of alkalinization and use of a silver nitrate (AgNO3) catalyst was also assessed. Methods: Control and urine test specimens containing from 0.5 to 800 mmol/L ACET, AcAc, and BOHB were prepared. Urine specimens were oxidized with H2O2 (3%) 1:9 (H2O2:urine), alkalinized with potassium hydroxide (KOH; 10%), exposed to AgNO3 sticks, or altered with a combination of these methods in a random fashion. Three emergency physicians (EPs) blinded to the preparation technique evaluated urine dipsticks (Multistix, Bayer Corp.) placed in the specimens for "ketones." Results: Multistix detected AcAc appropriately; ACET was detected only at high concentrations of ≥600 mmol/L. Multistix failed to measure BOHB at all concentrations tested. H2O2 improved urinary BOHB detection, although not to clinically relevant levels (40 mmol/L). Alkalinization and AgNO3 sticks did not improve BOHB detection beyond this threshold. Conclusions: Addition of H2O2 (3%), alkalinization, or AgNO3 sticks did not improve clinically meaningful urine BOHB detection. Clinicians should use direct methods to detect BOHB when suspected. © 2008 by the Society for Academic Emergency Medicine.