Hypokalemia resident survival guide
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby, M.D. [2]
Overview
Hypokalemia is defined as plasma potassium concentration less than 3.5 mEq/L. Hypokalemia may present as ileus, muscle cramps, rhabdomyolysis, and polyuria. Electrocardiography findings may include U wave, flat or inverted T waves, prolonged QT interval, and ventricular ectopy.
Causes
Life Threatening Causes
Life-threatening conditions which may result in death or permanent disability within 24 hours if left untreated. Severe hypokalemia may be life-threatening and must be treated as such irrespective of the underlying cause.
Common Causes
Shown below is a table summarizing the different pathophysiological processes that can lead to hypokalemia.
Trans-cellular shifts | Renal loss | GI loss | Increased hematopoiesis | Decreased intake of potassium | |
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Subject is normo or hypotensive Associated with alkalosis
Variable acid/base status |
Subject is hypertensive
Secondary hyperaldosteronism
Non aldosterone increase in mineralcorticoid
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Associated with metabolic acidosis Associated with metabolic alkalosis
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Diagnostic Algorithm
Shown below is an algorithm depicting the possible laboratory findings and their interpretation.
\div {\frac{urine_{osm}}{plasma_{osm}}} </math> }}Hypokalemia [K+] < 3.5 | |||||||||||||||||||||||||||||||||||||||||||||||
Order: ❑ 24 hours urinary K+ (UK) ❑ Transtubular potassium gradient (TTKG) <math> TTKG = {\frac{urine_K}{plasma_K | |||||||||||||||||||||||||||||||||||||||||||||||
UK > 15 mEq/L TTKG > 7 | UK < 15 mEq/L TTKG < 3 | ||||||||||||||||||||||||||||||||||||||||||||||
Renal loss of potassium | GI loss of potassium | ||||||||||||||||||||||||||||||||||||||||||||||
What is the blood pressure? | |||||||||||||||||||||||||||||||||||||||||||||||
Normal or ↓ | ↑ | ||||||||||||||||||||||||||||||||||||||||||||||
Check the acid/base status | Possible etiologies are: Primary aldosteronism Secondary aldosteronism Non aldosterone increase in mineralcorticoids | ||||||||||||||||||||||||||||||||||||||||||||||
Acidemia | Alkalemia | Variable | |||||||||||||||||||||||||||||||||||||||||||||
Check urinary chloride (UCl) | Hypomagnesemia | ↑ Aldosterone ↓ Renin | ↑ Aldosterone ↑ Renin | ↓ Aldosterone | |||||||||||||||||||||||||||||||||||||||||||
UCl < 20 | UCl > 20 | Primary aldosteronism | Secondary aldosteronism | Non aldosterone increase in mineralcorticoids | |||||||||||||||||||||||||||||||||||||||||||
Management
- Treat the underlying etiology.
- Potassium repletion for the deficit (for every 1 mEq/L decrease in potassium, there is 200 mEq loss of total body potassium):
- PO: 40 mEq KCL Q 4-6 hours
- IV (if urgent): 10 mEq/hour KCL
- Recheck potassium levels in 2-4 hours.
- Provide IV hydration if necessary.
Do's
- Avoid excessive potassium repletion, particularly in the cases of transcellual shifts of potassium that can be reversed when the initial cause of hypokalemia is treated.
- Treat low magnesium blood concentration.
Dont's
- If hydration is needed, do not administer dextrose solutions because dextrose increases insulin which can causes intracellular shift of potassium, and further exacerbates hypokalemia.