DESCRIPTION:
Potassium is the main cation of cell fluid. Potassium is also called cell electrolyte. The concentration of potassium in the intracellular space is about 40 times higher than in the extracellular space. In erythrocytes, the concentration of potassium is 92-105 mmol/L (about 22 times more than in plasma). Therefore, the concentration of potassium should not be determined in hemolyzed serum. The daily needs of the organism are 3-4 g (76-102 mol), which the organism receives through food. Potassium is resorbed in the small intestine. About 90% of potassium is excreted from the body in urine, and about 10% in stool. Potassium is filtered through the glomeruli, but about 90% is reabsorbed in the proximal tubules.
However, in the distal tubules, potassium is excreted again, because here – like hydrogen – it is replaced by sodium. Potassium excretion is regulated by aldosterone and to a lesser extent by corticosteroids. An increase in the concentration of potassium in the extracellular fluid leads to an increase in the secretion of potassium, and thus to an increased excretion of potassium in the urine (50-100 mmol/L is normally excreted). The consequence of this is a lowered concentration of potassium in the serum. There is normally 3.6 – 5.4 mmol/L of potassium in the serum. Hypokalemia occurs due to loss of potassium through increased diuresis, diarrhea, vomiting, and the like. Hyperkalemia occurs in conditions when the potassium ion moves from the cells to the extracellular fluid, during dehydration and unbalanced potassium therapy.
DETERMINATION:
Sample: Serum, plasma (ammonium heparinate;) Measurement unit: mmol/L. Separate serum or plasma from blood cells within 30 minutes from the time of blood collection. The sample is stable for 14 days at 2-8°C. The concentration of potassium is determined by the ion selective method.
CLINICAL SIGNIFICANCE:
Potassium values should always be interpreted after careful examination of the patient’s clinical condition. 1) Physiological changes in serum potassium concentration Pathological changes in potassium concentration A) Increased values of potassium concentration in: Arthropod hemorrhagic fever / Diabetes mellitus / Diabetic acidosis / Hyperparathyroidism / Hyperthyroidism / Adrenal gland hypofunction / Carcinoid syndrome / Chronic myeloid leukemia / Chronic renal failure / Metabolic acidosis / Polycythemia rubra vera / Pre-eclampsia / Acquired syndrome immunodeficiency (AIDS) / Heat stroke B) Decreased values of potassium concentration in: Acute intermittent porphyria / Acute myeloid leukemia / Acute renal failure / Alcoholic cirrhosis / Cirrhosis of the liver (patients with edema and ascites) / Folic acid deficiency / Diabetes mellitus / Familial periodic paralysis / Gitelman syndrome / Hepatolenticular degeneration / Hyperaldosteronism / Adrenal gland hyperfunction / Hypokalemia / Carcinoma of the pancreas / Cholera / Congestive cardiac arrest / Malignant hypertension / Metabolic alkalosis / Peptic ulcer / Pernicious anemia / Vomiting / Diarrhea / Trauma / Ulcerative colitis / Whipple’s disease / Zollinger-Ellison syndrome
RISK FACTORS:
Reduced values:
Alcoholism Starvation Vascular ligation >1 min. (6.2%) Shock Pregnancy Fever
Increased values:
Dehydration Age Hemolysis in vitro (Hb >0.5 g/L) Hemolysis in vivo (Hb >0.5 g/L) Whole blood storage Diet rich in potassium Stress Physical exertion (increased muscle activity)
EFFECT OF DRUGS:
Reduced values:
sulfasalazine
Increased values:
cefotaxime, cisplatin, fluorides, fluosol-DA, gamma-globulins, iodides, procainamide
RESULT:
The reference interval depends on gender, age and work method. The reference interval is displayed on each validated result.
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