Hypokalemia
(Redirected from Potassium)
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
- Central nervous system
- Gastrointestinal
- Renal
- Cardiovascular
Differential Diagnosis[1]
Intracellular Shift
- Alkalosis (each 0.10 rise in pH causes 0.5 decrease)
- Insulin
- Beta agonists
- Hypokalemic periodic paralysis
Decreased intake
- Special diets or those low in potassium
- Chronic alcohol abuse
- Fasting
- Eating disorders
Increased loss
- GI
- Renal
- Diuretics, especially loop and thiazide diuretics
- Osmotic diuresis (late-presenting DKA)
- Hyperaldosteronism
- Renal tubular acidosis
- Hypercalcemia
- Hypomagnesemia
- Increased sweat loss
- Heavy exercise
- Heat stroke
- Fever
Drugs
- Penicillins
- Lithium
- L-dopa
- Theophylline, methylxanthines (e.g. caffeine
- Insulin
- Barium
- Quinine
- Catecholamines
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:
- ST segment depression or flattened or inverted T wave
- U wave (V4-V6)
- QT prolongation
- Premature ventricular contraction, other ectopy, or any new arrhythmia
- Careful review of medication list
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
- Must be given in dilute solutions at slow rate (10 mEq/hour) to minimize side effects (burning/phlebitis) and cardiac toxicity
- 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
- ↑ 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§ionid=109381281
- ↑ 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.
- ↑ Potassium Supplement (Oral Route, Parenteral Route) from Mayo Clinic
- ↑ Slovis, Corey. "Electrolyte Emergencies". Presentation.
- ↑ Goyal A et al. Serum Potassium Levels and Mortality in Acute Myocardial Infarction. JAMA. 2012;307(2):157-164.
- ↑ EM:RAP 2018 August Electrolyte Emergencies - Part 1 - All Things Potassium