Symptoms to Diagnosis

The devil is in the details: Approach to refractory hypokalemia

Carmen Elena Cervantes, MD, Karthik Meiyappan Udayappan, MD and Duvuru Geetha, MBBS, MD
Cleveland Clinic Journal of Medicine April 2022, 89 (4) 182-188; DOI: https://doi.org/10.3949/ccjm.89a.21013

Article Figures & Data

Figures

  • Figure 1
    Figure 1

    Metabolic alkalosis should first be evaluated by obtaining a random urine chloride. This step helps classify it as volume-responsive (urine chloride < 20 mmol/L) or volume-resistant (urine chloride ≥ 20 mmol/L). The latter is further divided based on the presence or absence of hypertension.

  • Figure 2
    Figure 2

    Processes of mineralocorticoid excess and effect of spironolactone. In the principal cells in the collecting ducts of the kidney, activation of the mineralocorticoid receptor (MR) increases the transcription, translation, and insertion of more epithelial sodium channels (ENaC) in the luminal side. Cortisol and aldosterone have the same affinity for the mineralocorticoid receptor, but aldosterone is present in higher concentrations. Activation of the mineralocorticoid receptor stimulates a cascade of intracellular reactions that results in increased expression of the epithelial sodium channel. Spironolactone blocks the mineralocorticoid receptor. The enzyme 11-β hydroxysteroid dehydrogenase (HSD) type 2 converts cortisol to its inactive metabolite, cortisone. This enzyme can be absent in apparent mineralocorticoid excess, or it can be inhibited by licorice or posaconazole. Notably, the increased number of epithelial sodium channels leads to sodium (Na+) reabsorption from the tubular lumen. To maintain electroneutrality, another positive ion (K+) is secreted into the tubular lumen through the renal outer medullary potassium channel (ROMK).

Tables

  • TABLE 1

    The patient’s laboratory values on admission

    TestResultsaReference range
    Sodium140 mmol/L132-148 mmol/L
    Potassium2.1 mmol/L3.5-5.0 mmol/L
    Chloride93 mmol/L98-111 mmol/L
    Bicarbonate> 45 mmol/L23-32 mmol/L
    Blood urea nitrogen30 mg/dL10-25 mg/dL
    Creatinine1.11 mg/dL0.7-1.4 mg/dL
    Calcium8.0 mg/dL8.4-10.5 mg/dL
    Albumin2.7 g/dL3.5-5.0 g/dL
    Hemoglobin A1c6.8%< 5.7%
    Hemoglobin14.5 g/dL12-16 g/dL
    White blood cell count14.3 x 109/L3.7-11.0 x 109/L
    Platelet count79 x 109/L140-400 x 109/L
    Alanine aminotransferase79 U/L0-45 U/L
    Aspartate aminotransferase81 U/L7-40 U/L
    Alkaline phosphatase129 U/L40-150 U/L
    Bilirubin, total1.4 mg/dL0-1.5 mg/dL
    Arterial blood gasses
     PH7.557.35-7.45
     Pco254 mm Hg35-45 mm Hg
     PO234 mm Hg75-100 mm Hg
     Bicarbonate47 mmol/L18-23 mmol/L

    • ↵a Abnormal results are shown in bold.

  • TABLE 2

    Additional workup

    TestsResultsaReference range
    Urine potassium, random68 mmol/L17.0–99.0 mmol/L
    Urine chloride, random32 mmol/L30–260 mmol/L
    Urine creatinine, random80 mg/dL40–278 mg/dL
    Serum renin2.17 ng/mL0.25–5.82 ng/mL
    Serum aldosterone< 1 ng/dL3–16 ng/dL

    • ↵a Abnormal results are shown in bold.

  • TABLE 3

    Further additional workup

    TestsResultsaReference range
    Cortisol, AM level125 μg/dL6-26 μg/dL
    24-hour urinary cortisol excretion16,080 μg/24 hours4-50 μg/24 hours
    Adrenocorticotropichormone1,140 μg/mL6-50 μg/mL

    • ↵a Abnormal results are shown in bold.

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