Hypokalemia resident survival guide: Difference between revisions
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{{Family tree | | | | | | | A01 | | | | | A01= Order: <br> <div style="float: left; text-align: left; width: 15em; padding:1em;">❑ 24 hours urinary K<sup>+</sup> (U<sub>K</sub>)<br> ❑ Transtubular potassium gradient (TTKG) <br> <math> TTKG = {\frac{urine_K}{plasma_K}} \div {\frac{urine_{osm}}{plasma_{osm}}} </math> </div>}} | {{Family tree | | | | | | | A01 | | | | | A01= Order: <br> <div style="float: left; text-align: left; width: 15em; padding:1em;">❑ 24 hours urinary K<sup>+</sup> (U<sub>K</sub>)<br> ❑ Transtubular potassium gradient (TTKG) <br> <math> TTKG = {\frac{urine_K}{plasma_K}} \div {\frac{urine_{osm}}{plasma_{osm}}} </math> </div>}} | ||
{{Family tree | | | | | |,|-|^|-|.| | | | | | | }} | {{Family tree | | | | | |,|-|^|-|.| | | | | | | }} | ||
{{Family tree | | | | | B01 | | B02 | B01= '''U<sub>K</sub> > | {{Family tree | | | | | B01 | | B02 | B01= '''U<sub>K</sub> > 25-30 mEq/L/day''' <br> '''TTKG > 7'''| B02= '''U<sub>K</sub> < 25 mEq/L/day''' <br> '''TTKG < 3'''| }} | ||
{{Family tree | | | | | |!| | | |!| | | }} | {{Family tree | | | | | |!| | | |!| | | }} | ||
{{Family tree | | | | | C01 | | C02 | C01= '''Renal loss of potassium'''|C02= '''GI loss of potassium'''| }} | {{Family tree | | | | | C01 | | C02 | C01= '''Renal loss of potassium'''|C02= '''GI loss of potassium'''| }} |
Revision as of 20:24, 26 October 2014
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 | |
|
Subject is normo or hypotensive Associated with alkalosis
Variable acid/base status |
Subject is hypertensive
Secondary hyperaldosteronism
Non aldosterone increase in mineralcorticoid
|
Associated with metabolic acidosis Associated with metabolic alkalosis
|
|
|
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 > 25-30 mEq/L/day TTKG > 7 | UK < 25 mEq/L/day 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.