Hypokalemia

(Redirected from HypoK)

Background

  • Hypokalemia is one of the most common electrolyte derangements
  • While mild-moderate hypokalemia can be asymptomatic or mildly symptomatic, severe hypokalemia can be fatal
  • Potassium is predominantly intracellular; important in maintaining cell membrane potential, especially in cardiac/nerve/muscle tissue
  • While the renal and endocrine systems regulate total body potassium, transient physiologic shifts can greatly alter measured serum potassium

Clinical Features


Differential Diagnosis[1]

Differential diagnosis of hypokalemia

Intracellular Shift

Decreased intake

  • Special diets or those low in potassium
  • Chronic alcohol abuse
  • Fasting
  • Eating disorders

Increased loss

Drugs

Other

  • Acute leukemia and lymphomas
  • Recovery from megaloblastic anemia
  • Hypothermia (accidental or induced)

Evaluation

  • Serum potassium level is diagnostic
    • Normal = 3.5-5meq/L
    • Moderate hypokalemia = between 2.5 and 3.0 meq/L. Severe hypokalemia = <2.5meq/L
  • Always check magnesium
    • Na+/K+ ATPase pump requires Mg to function, therefore low Mg can lead to refractory hypoK
  • Obtain ECG. Suggestive findings include:
  • Careful review of medication list


ECG Hypokalemia.jpg

Management

  • Potassium repletion (PO or IV)
    • Every 10mEq KCl → serum K ↑ ~0.1mEq/L
    • PO preferred; if symptomatic or level is <2.5, both oral and IV should be given
    • Note: Administration of KCl during an ongoing intracellular shift can lead to rebound hyperkalemia when the shift reverses
    • Potassium chloride is usually preferred; other forms of potassium salts (potassium bicarbonate, potassium phosphate) increases serum potassium slower[2]
    • Consider repeating chem panel 3-4 hrs later to check for response; check faster if giving at a faster rate
  • Oral potassium
    • Inexpensive, well-tolerated, and rapidly absorbed
    • Consider giving 20 mEq q3hr or 40 mEq PO q6hr
    • KCl tablet (elixir form available but has poor taste)
    • K-Dur (extended release tablet) is large and may be difficult to swallow
    • If sending patient home can also increase food intake of potassium as an alternative or supplementing potassium tablets. Printable table that can be given to the patient available at this reference: [3].
  • Intravenous potassium
    • Must be given in dilute solutions at slow rate (10 mEq/hour) to minimize side effects (burning/phlebitis) and cardiac toxicity
      • If needing to infuse at 20 mEq/hr, consider infusion via central line or two peripheral lines
    • Consider runs of 10 mEq in 100 mL of water, each administered over 1 hr. Or 40-60 mEq in a 1000 mL bag, administered at a rate appropriate to type of IV access
    • Do not replete with dextrose-containing solutions since dextrose-induced insulin release can worsen hypokalemia
    • Continuous tele is recommended for both the underlying hypokalemia and the potassium administration
  • Also treat Hypomagnesemia if present
  • Re-check ECG after treatment [4]
  • Hypokalemia in acute or recent myocardial infarction places patients at much higher risk for ventricular fibrillation[5]
    • Previous studies and many professional organizations recommend maintaining K between 4.0 - 5.0 mEq/L in MI patients
    • However, more recent studies suggest 3.5 - 4.5 mEq/L results in the lowest mortality


Disposition

  • Based on underlying cause
  • One admission criteria is potassium less than 3.0 meq/L and a QTc that is close to or more than 500 msec. [6]

See Also

External Links

References

  1. ↑ In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. McGraw-Hill; Accessed November 29, 2020. https://accessmedicine.mhmedical.com/content.aspx?bookid=1658&sectionid=109381281
  2. ↑ Cohn JN, Kowey PR, Whelton PK, Prisant LM. New guidelines for potassium replacement in clinical practice: a contemporary review by the National Council on Potassium in Clinical Practice. Arch Intern Med. 2000 Sep 11;160(16):2429-36. doi: 10.1001/archinte.160.16.2429. PMID: 10979053.
  3. ↑ Potassium Supplement (Oral Route, Parenteral Route) from Mayo Clinic
  4. ↑ Slovis, Corey. "Electrolyte Emergencies". Presentation.
  5. ↑ Goyal A et al. Serum Potassium Levels and Mortality in Acute Myocardial Infarction. JAMA. 2012;307(2):157-164.
  6. ↑ EM:RAP 2018 August Electrolyte Emergencies - Part 1 - All Things Potassium
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