Hypokalemia resident survival guide
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Hypokalemia is defined as plasma potassium levels less than 3.5 mEq/L
Causes
Life Threatening Causes
Life-threatening conditions which may result in death or permanent disability within 24 hours if left untreated.
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
|
Subject is hypertensive
Secondary hyperaldosteronism
|
Associated with metabolic acidosis
Associated with metabolic alkalosis
|
|
|
Diagnostic Algorithm
Shown below is an algorithm depicting the possible laboratory findings and their interpretation.
Hypokalemia [K+] < 3.5 | |||||||||||||||||||||||||||||||||||||||||||||||
Order: ❑ 24 hours urinary K+ (UK) ❑ Transtubular potassium gradient (TTKG) | |||||||||||||||||||||||||||||||||||||||||||||||
UK > 25-30 mEq/L TTKG > 7 | UK < 25 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
1) Hypokalemia may present as ileus, muscle cramps, rhabdomyolysis, and hypomagnesemia.
2) Treat the etiology.
3) For severe hypokalemia (K < 2.5 mEq/L)
- EKG findings show 'U' wave, flat or inverted T waves.
- Intravenous KCL 80 mEQ/L @ 10-15mEq/hr with oral KCL 40-80mEq/L
- Recheck potassium levels in 2-4 hours