Potassium is an important element from the group of alkali metals, which is counted among the electrolytes (blood salts). In this context, potassium is the main cation of intracellular fluid (98%) – fluid located inside the cell – along with various phosphate esters. It is important primarily for normal activity of nerves and muscles, but also for overall cellular function. The average daily potassium intake is between 40 and 120 mmol. Potassium is mainly excreted renally (“via the kidneys”), but excretion may be enteral (“via the intestines”) to a certain extent (up to circa 60%) in chronic renal insufficiency.
The process
Material needed
- Blood serum
- Or LiH plasma, spontaneous or collected urine (24 h urine).
Preparation of the patient
- Not necessary
Disruptive factors
- Avoid long venous congestion as well as strong suction during collection! (lead to hemolysis)
- Excessive activity of the forearm muscles (“pumping”) releases potassium from muscle cells (falsified and high results).
- Storage of whole blood longer than 2-4 h (leads to an artificial increase in the potassium value) Cause: the potassium concentration is 25 times higher in the erythrocytes (red blood cells) than in the plasma! An increase in potassium takes place even with slight hemolysis. This is not yet visible to the eye and may also affect only the platelets (blood platelets)!
Normal values – blood
| Standard values in mmol/l | |
| 1st week of life | 3,2-5,5 |
| 1st month of life (LM) | 3,4-6,0 |
| <6 LM | 3,5-5,6 |
| 6TH-12TH LM | 3,5-6,1 |
| > 1. year of life | 3,5-6,1 |
| Adult | 3,8-5,2 |
Normal values – urine
| Normal value in mmol/24 h | 30-100 |
When fasting, the value may drop.
Indications
- Suspected acid-base balance disorders.
Interpretation
Interpretation of elevated values (in serum; hyperkalemia (excess potassium)).
- Alcohol abuse (alcohol abuse)
- Acidosis – overacidification of the blood.
- Diabetes mellitus (diabetes)
- Hemolytic anemia – form of anemia in which the red blood cells are destroyed and potassium is released.
- Increase in total body potassium
- Tissue breakdown (hemolysis, trauma, tumors, radiation therapy, cytostatic drugs).
- Hypoaldosteronism (primary and secondary; Addison’s disease) – reduction of aldosterone in the blood, which regulates electrolyte (salt)-water balance.
- Renal insufficiency (kidney weakness).
- Increased intake of potassium; hyperkalemia (excess potassium) due to increased dietary potassium intake occurs only in patients with impaired renal function
- Medications – increase in total body potassium due to:
- ACE inhibitors (benazepril, captopril, cilazapril, enalapril, fosinopril, lisinopril, moexipril, peridopril, quinapril, ramipril, spirapril).
- Angiotension II receptor antagonists (AT-II-RB; ARB; angiotensin II receptor subtype 1 antagonists; angiotensin receptor blockers; AT1 receptor antagonists, AT1 receptor blockers, AT1 antagonists, AT1 blockers; angiotensin receptor blockers, sartans) – candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan.
- Aldosterone antagonists (amiloride, spironolactone, eplerenone).
- Beta blockers
- Non-selective beta-blockers (e.g., carvedilol, propranolol, soltalol).
- Selective beta-blockers (e.g., atenolol, bisoprolol, metoprolol).
- Digitalis – digitalis glycosides
- Heparin
- Non-steroidal anti-inflammatory drugs such as acetylsalicylic acid (ASA).
- For other medications, see “Hyperkalemia (excess potassium) due to medications.”
Interpretation of decreased values (in serum; hypokalemia (potassium deficiency)).
- Alimentary (nutritional)
- Excessive sodium intake (can lead to potassium depletion).
- Total parenteral nutrition – complete nutrition through the veins.
- Starvation
- Endocrinological causes
- Potassium shift into cells by insulin, epinephrine and aldosterone.
- Decrease in total body potassium – renal loss (loss through the kidneys) due to hyperaldosteronism (primary and secondary) – increase in blood aldosterone, which regulates salt-water balance.
- Metabolic (metabolic) disorders.
- Alkalosis (metabolic) – excessive alkalinity in the blood.
- Hypomagnesemia (magnesium deficiency) – the permeability of potassium through the potassium channels is increased, leading to renal potassium losses – in addition, the high permeability of potassium affects the myocardial action potential
- Decrease in total body potassium – renal loss (loss via the kidneys) due to renal tubular acidosis.
- Diseases
- Hypokalemic periodic paralysis (HTTP) – genetic disorder leading to circa one-hour flaccid paralysis (motor muscle paresis; e.g., leg paresis/leg weakness).
- Decrease in total body potassium – gastrointestinal loss (via the gastrointestinal tract) due to vomiting and diarrhea (diarrhea) or intestinal fistulas.
- Decrease in total body potassium – renal loss (loss via the kidneys) in renal insufficiency and osmotic diuresis in diabetes mellitus.
- Medication – lowering of total body potassium.
- Amphotericin B (antifungal; antifungal agent).
- Betamimetics (synonyms: β2-sympathomimetics, also β2-adrenoceptor agonists) – fenoterol, formoterol, hexoprenaline, indaceterol, olodaterol, ritodrine, salbutamol, salmeterol, terbutaline
- Diuretics
- Loop diuretics (etacrynic acid, furosemide, piretanide, torasemide).
- Thiazide diuretics (hydrochlorothiazide (HCT), benzthiazide, clopamide, chlortalidone (CTDN), chlorothiazide, hydroflumethiazide, indapamide, methyclothiazide, metolazone, polythiazide and trichloromethiazide, xipamide).
- Laxatives (laxatives) such as lactulose.
- For other medications, see “Hypokalemia (potassium deficiency) due to medications.”
- Increased demand
- Women respectively men ≥ 65 years (due to insufficient food intake, frequent use of medications – diuretics, laxatives).
- Discussed is an increased need for athletes and heavy workers (after several hours of continuous exercise about 300 mg potassium / liter are lost through sweat)
- Hypothermia (hypothermia)
- Poisoning with barium
- Other increased loss (sweating)
Other notes
- Pseudohyperkalemia, i.e., a falsely high serum potassium level, occurs when either erythrocytes (red blood cells), leukocytes (white blood cells), or platelets lyse (dissolve “in the test tube”) in vitro and release their potassium into the serum (hemolysis/dissolution of red blood cells). Other causes of pseudohyperkalemia include the occurrence of leukocytosis (> 50,000 leukocytes/mm3), hereditary spherocytosis (spherocytic anemia), incorrect blood collection (too long venous stasis → hemolysis) or after blood collection too long storage of the blood (leads to an artificial increase in potassium).
- Since the majority of potassium is intracellular, an electrocardiogram (ECG) should always be recorded if a disturbance in potassium concentration is suspected, in order to better detect disturbances.
- Calculation of potassium deficit: 1 mmol deviation of the potassium level corresponds approximately to a potassium deficiency of 100 mmol (1 mmol potassium corresponds to 39.1 mg).
- The normal requirement for potassium in women as well as men is 4,000 mg/d.