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Blood Electrolytes

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Indications:

Before different clinical presentations that may be suspected of fluid and electrolyte disorders, the test measures the major blood anions and cations:

– Cations are: sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg);

– Anions are: chlorine (Cl), bicarbonate (HCO3) and proteins.

It is the clinical examination which must guide the application.

The review also becomes important:

– In the monitoring of metabolic disease such as diabetes, hypertension.

– From kidney or liver disease;

– If dehydration is suspected, intracellular hydration, hyper- or hypokalemia (secondary aldosteronism in HTA), but also of hyponatremia in patients on diuretics, suffering from kidney disease.

Principle:

The balance of anions and cations is one of the conditions of the balance of the body, particularly its proper hydration;it is broken and the disorders may appear, biological first and clinics.

Technique:

Sampling 5 mL of venous blood on heparin tube:

– Quickly send to the laboratory;

– Reduce to a minimum the time of the withers;

– Do not make a fist to the patient;

– Absolutely avoid hemolysis.

Results:

Normal values:

cations mmol / L mEq / L anions mmol / L mEq / L
Na (sodium) 138-145 138-145 Cl (chlorine) 95 to 105 95 to 105
K (potassium) 3.8 to 5 4.52 HCO3 (bicarbonate) 22-28 22-28
Ca (Calcium) 2.25 to 2.55 5 protein 60-80 g / L 117
Mg (magnesium) 0.75 to 1 2

Sodium and potassium cations account for 95%, chlorine and bicarbonate, 85% of the anions.

The difference between cation and anion is called “anion gap”:

– It is increased in case of:

  – Kidney failure with acidosis and clearance less than 10mL / min,

  – Diabetic acidosis (buildup of anions)

  – Lactic acidosis

  – Toxic acidosis (salicylates, ethylene glycol)

  – Hypocalcemia, hypogammaglobulinemias (decrease cations);

– It is reduced in case of:

  – Cirrhosis (lower anions)

  – nephrotic syndrome,

  – Acute intoxication with lithium or IgG myeloma (cations increases).

Another parameter to consider is the measurement of plasma osmolality, which is obtained by the following calculation: osmolality = serum sodium mmol / L x 2 + glucose mmol / L + urea mmol / L:

– Its normal value of 300 mOsm / kg water;

– Plasma Hyperosmolality is due to:

  – Water deficit by inadequate intake or kidney damage,

  – A diabetic hyperosmolar coma, acute alcoholism, a massive ingestion of sea water;

– There are hypo-osmolality in case of:

  – Taking diuretics,

  – Acute adrenal insufficiency,

  – Vomiting, diarrhea.

Cost:

B20 Na, Cl, K

B40 plus HCO3 and protein.

Practical advice:

The chemistry panel is disrupted in case of large or hyperlipemia hyperprotéinémies: all components are lowered; the amount of water being reduced in proportion to the additional amount of protein and or lipids.

A simple additional examination, urinary electrolytes (removal of morning urine), information on the behavior of the kidney compared to pathology observed compared to a chemistry panel disorder.

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