Calcium Ca (ionized)

About half (45%) of the total plasma calcium binds to albumin (and only a small fraction of globulins) in a non-ionized and non-diffuse form, making it a physiologically inactive form. Small amounts (5%) of calcium are diffuse but not ionized, present in the form of citrate, phosphate and calcium bicarbonate. The rest of the plasma calcium is found in ionic or free form.

All the physiological effects of calcium (in muscle contraction, in the mechanisms of hormone secretion, in cell division, etc.) are exerted by its In ionized form (Ca2 +). Free calcium makes up 43-50% of total calcium. Its concentration varies during the day: the minimum concentration is at 20:00, the maximum - at 2: 00-4: 00 in the morning. Ionized calcium levels are maintained by the active form of parathyroid hormone, calcitonin and vitamin D3. The production of these hormones, in turn, depends on Ca2 + levels.

Its concentration in the blood is influenced by many factors - proteins, magnesium (in case of hypocalcemia it is necessary to determine the concentration of magnesium), acid-base balance (alkalosis increases the level of binding and decreases the concentration of ionized calcium; .

Determination of free calcium makes it possible to more accurately assess the state of calcium metabolism, especially in patients undergoing surgery and resuscitation and receiving heparin, bicarbonate, calcium and magnesium supplements.

The determination of ionized calcium is more informative than the determination of total calcium for the diagnostics of hypercalcemic conditions, particularly in primary hyperparathyroidism (characterized by an increase in the concentration of free calcium in the blood and an unchanged level of total calcium) in oncology and dialysis patients.

Serum total calcium levels decrease during pregnancy along with a decrease in albumin concentration, although free calcium levels remain in the normal range.

Levels of ionized calcium at which tetany and seizures may develop: <0,8 mmol / L; Critical, life-threatening level: <0,7 mmol / L (according to some reports - <0,5 mmol / L).

When to take a calcium test?

• Evaluation of biologically active calcium fraction in pregnant women and newborns;
• Diseases of the parathyroid glands;
• Bone tissue diseases;
• Chronic kidney disease;
• Liver diseases;
• Tetany;
• Extensive trauma;
• Sepsis;
• Burns;
• Pancreatitis;
• Acidosis;
• Multiorgan failure;
• Malignant hypercalcemia;
• Malignant tumors, etc.
• Transfusion of citrate-containing blood;
• Taking heparin;
• Surgical interventions;
• Dialysis;
• Post-extracorporeal circulation period, etc .;

How to prepare for the test?

The test should be performed on an empty stomach.

Research material

Venous blood

Possible interpretation of the results

The concentration of ionized calcium increases:

• Primary hyperparathyroidism;
• Ectopic tumors that produce parathyroid hormone;
• Excess intake of vitamin D;
• Malignant tumors and metastases;
• Acidosis.

The concentration of ionized calcium decreases:

• Primary hypoparathyroidism, pseudohypoparathyroidism;
• Vitamin D deficiency;
• Sepsis;
• Acute pancreatitis;
• Renal failure;
• Severe skeletal muscle injuries;
• Hemodialysis with low calcium concentrations in dialysis;
• After transfusion of citrate-containing blood;
• After extensive injuries, surgical interventions;
• Burns;
• Multiorgan failure;
• Magnesium deficiency;
• Alkalosis;
• Hypernatremia;
• Atrophic gastritis.

Resources

https://spravochnik.synevo.ua/ru/klinicheskaia-himia/calciy-ionizirovanniy.html
https://www.synevo.ro/shop/calciu-ionic/