potassium (K)   

Edited by: Joe Hing Kwok Chu

Potassium acts as an important cation of the intracellular fluid. It is necessary for the transmission of nerve impulses and influences the acid-alkaline balance, osmotic pressure, and cellular membrane potential.

The serum level of K is influenced by changes in water and electrolyte balance in patients with certain endocrine disorders. Abnormal levels of K can cause toxicity for the heart.

Blood tests reflect only the potassium levels in the serium, and do not indicate the amount of potassium within the cells.

The following can interfere with test results:

• Use of tourniquet increases level.

• trauma during taking blood sample increases level

• Over hydration decreases level.

• Dehydration increases level.

• Hemolysis of the specimen increases level.

• Drugs that cause increased levels: potassium sparing diuretics (Aldactone, Dyrenium), penicillin G potassium, cephaloridine (Loridin), heparin, epinephrine, intravenous histamine, marijuana, isoniazid.

• Drugs causing decreased levels: potassium wasting diuretics, steroids, gentamicin, amphotericin, polymyxin B, bicarbonate, insulin, laxatives, lithium carbonate, sodium polystyrene sulfonate (Kayexalate), salicylates.

• High WBC counts increase level.

• High platelet counts increase level.

Clinical Implications

Hyperkalemia (high in potassium)

• Kidney failure. 

• Addison's disease.

• Massive tissue trauma.

• Any cause of significant metabolic acidosis such as lactic acidosis and diabetic ketoacidosis.

• Myeloproliferative disease such as thrombocytosis.

Hypokalemia (low in potassium)

• Diuretic therapy without potassium chloride supplementation.

• Hypomagnesemia.

• Hyper aldosteronism.

• Liver disease with ascites.

• Excessive ingestion of licorice (gan cao).

• Anti inflammatory drugs, indomethacin, phenylbutazone, steroids and sex hormones, particularly estrogens.

• Conditions associated with hyper-reninemia, in which an excessive amount of renin introduced into the system causes secondary aldosteronenia.

• Crash diets with inadequate intake of potassium.

• Chronic stress which increases adrenocortical hormone.

• Chronic diarrhea, malabsorption syndrome.

• Perspiration and chronic fever.

• Kidney-caused  loss of of potassium.

• Over intake of water.

See: Food high in potassium

See: hypokalemic periodic paralysis