DESCRIPTION:
In the body, sodium is found 98% in the extracellular fluid, and only 2% intracellularly. 8-15 g of NaCl is taken into the body daily through food. Almost all sodium chloride is absorbed in the small intestine. Sodium passes in the kidney into primary urine. 85% of sodium is reabsorbed in the proximal tubules, and 14.5% in the distal parts of the tubules. Only about 0.5% of sodium is excreted in the urine. Reabsorption of sodium in the tubules also depends on the concentration of the hormone aldosterone (increases sodium reabsorption). In the tubules, sodium is replaced by hydrogen ion (maintenance of acid-base balance). Sodium excretion depends on its concentration in the blood (135 – 146 mmol/L). 50-200 mmol/L of sodium is excreted daily in the urine. The concentration of sodium in the serum is relatively constant. Changes in sodium concentration are most often closely related to changes in water volume.
DETERMINATION:
The concentration of sodium is determined by the ion selective method. The sample for analysis is serum or urine. The stability of sodium is 14 days at 2°C – 8°C. The sample for analysis must not be hemolytic.
CLINICAL SIGNIFICANCE:
1) Physiological changes in sodium concentration 2) Pathological changes in sodium concentration A) Increased values of sodium concentration in: Acute lymphatic leukemia / Acute myeloid leukemia / Diabetes insipidus / Diabetic acidosis / Adrenal gland hyperfunction / Cholera / Congestive cardiac arrest / Chronic lymphatic leukemia / Chronic myeloid leukemia / Chronic renal failure / Non-Hodgkin’s lymphoma / Peritonitis / Vomiting / Diarrhea / Liver failure B) Decreased values of sodium concentration in: Acute intermittent porphyria / Acute myocardial infarction / Acute poststreptococcal glomerulonephritis / Acute renal failure / Alcoholic cirrhosis / Bacillary dysentery / Bacterial meningitis / Benign brain and CNS neoplasms / Biliary cirrhosis / Cerebral hemorrhages / Cerebral tumors / Liver cirrhosis / Diabetes mellitus / Diabetic acidosis / Encephalomyelitis / Essential hypertension / Gastroenteritis and colitis / Hyperlipoproteinemia type V / Adrenal gland hypofunction / Hypothyroidism / Lung cancer / Congestive heart failure / Chronic renal failure / Malaria / Burns / Proximal renal tubular acidosis / Diarrhea / Reye’s syndrome / Secondary malignant neoplasms of the brain / Acquired immunodeficiency syndrome (AIDS, AIDS) / Subacute thyroiditis / Typhus / Tuberculosis of the lungs / Tuberculous meningitis / Ulcerative colitis / Urethritis
RISK FACTORS:
Reduced values:
Bilirubin >60 micro mol/L Citrates (decrease in Na concentration up to 7.8 mmol/L) Age Ethanol (up to 6.9%) Heparin (vacutainers) – lower values in ISA methods than in methods with flame photometry Poor diet Menstrual cycle (luteal phase) Insufficient salt intake Misdiagnosed hyponatremia due to marked hyperproteinemia and hypertriglyceridemia Triglycerides >2.9 mmol/L Pregnancy
Increased values:
Anticoagulants with sodium (Na-oxalate, Na-heparinate, etc.) Dehydration Child rich in sodium Season: summer Calcium Blood taken with anticoagulants containing sodium Menopause Oral contraceptives Stress Trichloroacetic acid
EFFECT OF DRUGS:
Reduced values:
bicarbonates, hyoscine-N-butylbromide
Increased values:
ampicillin, cefotaxime, cisplatin, fluorides, fluosol-DA, gamma-globulin, potassium, carbamazepine, nitrofurantoin, norphenephrine, valproic acid
RESULT:
The reference interval depends on gender, age and the method of determination. The reference interval is displayed on each validated result.
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