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Abstract: PO1175

Mind the Gap: An Anion Gap of 52 Fully Explained

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Avula, Uma Mahesh R., The University of Mississippi Medical Center, Jackson, Mississippi, United States
  • Harris, Liliia, The University of Mississippi Medical Center, Jackson, Mississippi, United States
  • Shafi, Tariq, The University of Mississippi Medical Center, Jackson, Mississippi, United States
  • Dossabhoy, Neville R., The University of Mississippi Medical Center, Jackson, Mississippi, United States
Introduction

The Anion Gap (AG) remains the main clinical tool to elucidate acid-base disturbances in patients with metabolic acidosis. We present a case with an extremely elevated AG of 52 mmol/L, and describe our search for its biochemical explanation.

Case Description

A 66-year-old female was admitted with loss of consciousness, shock, and severe acute kidney injury. She had type 2 diabetes mellitus, treated with metformin. At presentation, she had an AG of 52 mmol/L and osmolal gap of 34 mOsm/kg. Her arterial blood gas showed: pH <7, HCO3 7.5 mmol/L, pCO2 16 mm/Hg. Phosphorus level was unusually high, 21.3 mg/dL, with unknown etiology. There was no history of enema or laxative use. A significant contributor of AG was lactate at 14.5, given her history of metformin use. Urine drug screen was positive for amphetamines. The volatile alcohol panel was positive for acetone; methanol, ethanol, ethylene glycol and isopropyl alcohol were not detected. Continuous venovenous hemofiltration (CVVH) was initiated. After 3 days, renal function started recovering, lactate and phosphorus levels normalized and AG closed. The patient did not need CVVH thereafter. Two months later, the patient was discharged to a nursing facility in a stable condition.

Discussion

Extremely elevated AG of 52 in this patient can be explained by a rise in concentrations of organic acid anions, lactate, ketoacids, hyperphosphatemia, and retention anions.

Explanation of the high AG: The Figure describes the calculation of AG. In this patient, phosphate was a major contributor to the AG.