Potassium
Background
- Primary intracellular cation; critical for cardiac and neuromuscular function
- Only ~2% of total body potassium is extracellular; small changes in serum levels can be clinically significant
Normal Values
- Normal: 3.5-5.0 mEq/L
- Hypokalemia: <3.5 mEq/L
- Hyperkalemia: >5.0 mEq/L
Interpretation
- Hemolyzed specimens are the most common cause of a falsely elevated potassium
- Hypokalemia is often caused by GI losses, diuretics, or inadequate intake
- ECG changes: U waves, flattened T waves, ST depression
- Replace both potassium and magnesium (hypomagnesemia impairs K repletion)
- Hyperkalemia is a life-threatening emergency when >6.5 mEq/L or with ECG changes
- ECG progression: peaked T waves, widened QRS, sine wave, asystole
- Treat with calcium (membrane stabilization), insulin + glucose (intracellular shift), and elimination (kayexalate, dialysis)[1]
See Also
References
- ↑ Palmer BF. Managing hyperkalemia caused by inhibitors of the renin-angiotensin-aldosterone system. N Engl J Med. 2004; 351(6):585-592. PMID 15295051.