Definition
cK+(P) is the concentration of potassium (K+) in plasma. The systematic symbol for arterial blood is cK+(aP). The analyzer symbol may be K+ or cK+.
What does cK+ tell you
The body has a total potassium level of 3,000-4,000 mmol, of which the major part is intracellular. The plasma (and the extracellular fluid) only contains about 4 mmol/L, totaling about 50 mmol (the extracellular fluid is about 12 L).
Although extracellular potassium only accounts for 1-2 % of the total potassium, it is of great importance since one of its main functions is to mediate the regulation of the entire potassium balance of the organism. A normal potassium level is essential to regulate cardiac function. Values outside the range 2.5-7.0 mmol/L are lethal.
Reference ranges
cK+(aP) reference range (adult): 3.4-4.5
disclaimer
Clinical interpretation
A. Low cK+ can be caused by:
- Forced diuresis (e.g., diuretic treatment, hypercalcemia, diabetes mellitus)
- Diarrhea
- Vomiting or gastric aspiration
- Respiratory or metabolic alkalosis
- Primary, or secondary (i.e., in hypovolemia or heart failure), hyperaldosteronism
- Magnesium depletion
B. High cK+ can be caused by:
- Renal failure
- Endogenous (i.e., lactate, ketones, in sepsis) metabolic acidosis
- Toxic metabolic acidosis (salicylate, methanol, etc.
Considerations
High values of cK+ can be caused by hemolysis of the red cells in a blood sample. This is typically seen following too vigorous aspiration and in capillary samples (poor sampling technique).
For more information, go to Preanalytical considerations.
