Blood Chloride (Cl^–)

Sample for Blood Chloride Cl¯

1. It is done on the serum or plasma of the patient.
2. Except for emergency collect fasting samples because there is a slight decrease after the meal.
3. Chloride is estimated in sweat to rule out cystic fibrosis.
4. Other samples are CSF and 24 hours of urine.

Purpose of the test (Indications)

1. As a part of electrolytes, acid-base balance.
   1. It gives status for hydration.
2. For the diagnosis of cystic fibrosis.

Precautions for Blood Chloride (Cl^–)

1. Separate serum or plasma from the cells, as a change in pH, will alter the distribution of Chloride.
2. Avoid hemolysis.
3. Serum, plasma, and urine are stable for one week at 1 to 4 °C or room temperature.
4. A frozen sample can be kept for one year.
5. Drugs that may increase the chloride level are ammonium chloride, acetazolamide, cortisones, androgens, and estrogens.
6. Drugs that may decrease the chloride level are aldosterone, corticosteroids, thiazide diuretics, and loop diuretics.

Definition of blood chloride (Cl^–):

1. Chloride is the most abundant extracellular anion.
2. The same conditions affect chloride, which affects sodium (the most abundant extracellular cation).

Pathophysiology of  Blood Chloride (Cl^–)

1. Chloride is the most abundant extracellular anion.
2. Chloride is the major negative electrolyte(anion) in the extracellular fluid.
   1. Chloride with sodium represents the majority of the osmotically active constituents of plasma. Thus, the serum chloride level changes in the same direction as the sodium level, except for a few conditions. If the serum sodium is low, then serum chloride will also be low.
3. The interstitial plasma fluid of chloride anion is 103 mmol/L.
4. Its intracellular fluid (RBC) concentration is 45 to 54 mmol/L.
5. While the intracellular fluid of other tissue is only 1 mmol/L.
6. Most physicians advise “electrolytes panel or profile,” which includes:
   1. Sodium.
   2. Potassium.
   3. Chloride.
   4. Bicarbonate.

Chloride absorption and excretion:

1. Chloride ions in the food are absorbed entirely in the intestine.
   1. They are filtered from the plasma at the glomerular level and passively reabsorbed, along with Na⁺ in the proximal tubules.
2. Chloride interacts with sodium to maintain the osmotic pressure of blood.
3. Its main purpose is to maintain the electrical neutrality of salt with sodium.
4. Aldosterone increases the reabsorption of sodium and Chloride to maintain neutrality.
5. Chloride acts as a buffer to help in acid-base balance.
   1. The concentration of the Cl^– changes inversely with the changes in the concentration of HCO₃^–.

6. Chloride is filtered at the glomerulus passively and reabsorbed at proximal tubules. Further absorption at the loop of Henle.
   1. There is a chloride pump in the ascending limb of the loop of Henle.
   2. Sodium is absorbed passively, while Chloride is absorbed actively by the pump.
   3. Excess Chloride is excreted in the urine and sweat.

Functions of Blood Chloride (Cl^–):

1. Maintenance of water balance and osmotic pressure with the help of sodium.
2. Chloride moves into cells in exchange for bicarbonate produced in the cells.
3. It can maintain electrical neutrality.
4. It helps as a buffer to help in the acid-base balance.
5. Anion-cation balance in the extracellular fluid compartment.
6. Chloride provides electroneutrality, particularly with Na⁺.

Blood Chloride (Cl-): Chloride maintains electrolyte balance.

The normal level of Blood Chloride (Cl^–)

Source 1

1. Serum = 95 to 105 meq / L (98 to 106 mmol/L)
2. Urine = 110 to 250 meq/ 24 hours
3. Sweat:
   1. Normal = 5 to 40 meq/L
   2. Marginal value =  30 to 70 meq/L
   3. Cystic fibrosis = 60 to 200 meq/L
4. CSF :
   1. Infant  = 110 to 130 meq/L
   2. Adult  =  118 to 132 meq/L
      1. These are 15% higher than those in serum.
5. Saliva without stimulation  =  5 to 20 meq/L

Other Sources 

Cystic fibrosis

1. Cystic fibrosis (mucoviscidosis) or fibrocystic disease of the pancreas is the most common lethal autosomal recessive. an inherited disorder in Europe.
2. In Europe, it is estimated 1 in 2,000 live births.
3. In Afro-Americans, the incidence is 2% of that in Europe.
4. It is rare in Asians.

Pathology of cystic fibrosis:

1. Around 90% of the homozygotes have symptoms predominantly resulting from damage to mucus-producing glands.
2. Non-mucus-producing glands may also be affected.
3. The mucus is very thick, which can plug the ducts and lead to obstructive complications.
4. In the lungs, it leads to recurrent bronchopneumonia. This is a very serious complication.
5. Pseudomonas and staphylococcus aureus are the common pathogens.
6. The next complication is the complete or partial destruction of the exocrine portion of the pancreas, and this will end up in various conditions like:
   1. Malabsorption.
   2. Steatorrhea.
   3. Digestive disturbances.
   4. Malnutrition.
7. A less common complication is biliary cirrhosis.

Sweat test for cystic fibrosis:

Procedure to collect the sweat:

1. Sweat is collected in a plastic bag or by iontophoresis.
2. Sweat is induced by sweat-stimulating agents like the pilocarpine.
3. Iontophoresis consists of two small electrodes that create a tiny electric current.
4. Sweat is collected in the small gauze pad.
5. This procedure is painless.

Sweat test interpretation:

1. The level of sodium and chloride is higher in patients with cystic fibrosis.
2. For a definite diagnosis, sweat is collected. The sample should weigh >50 mg, and weighing <50 mg is inadequate.
3. In children, sweat sodium >70 meq/L and chloride >60 meq/L are abnormal and are diagnostic of cystic fibrosis.
4. Sodium and chloride may be raised in the first three days of life and then decrease to childhood level by 4th day.
5. The sample should not be collected from the palm as there is an increased concentration of sodium and chloride (electrolytes).

Signs and symptoms of Hypochloremia:

1. There is the loss of Cl^–, usually resulting from hyponatremia or elevated HCO3^– concentration, as in metabolic alkalosis.
   1. This will develop with vomiting and loss of HCL.
   2. Hypochloremia characterizes cystic fibrosis.
   3. Restricted use of salt or in use of diuretics is accompanied by Cl^– deficiency.
2. There is hyperstimulation of the nervous system and muscles.
3. Shallow breathing.
4. Hypotension.
5. Tetany.

Signs and symptoms of Hyperchloremia

1. This occurs when there is too much sodium or too little bicarbonate.
   1. More than a normal amount of Cl ^– can be expected with hypernatremia or metabolic acidosis.
   2. Ingestion of excessive Cl^– accompanies the use of an ammonium chloride diuretic.
2. Usually, no specific symptoms are associated with chloride excess.
   1. There are lethargy and weakness.
   2. Deep breathing.

Increased level of Blood Chloride (Cl^–) (Hyperchloremia):

1. urinary tract obstruction, glomerulonephritis, renal tubular acidosis, and acute renal failure.
2. Diabetes Insipidus.
3. Salicylate intoxication.
4. Prolonged diarrhea with the loss of sodium bicarbonate.
5. Respiratory alkalosis.
6. Some cases of primary hyperparathyroidism.
7. Maybe because of excessive intake.
8. Eclampsia.
9. Cushing syndrome.
10. Renal tubular acidosis.
11. Dehydration.
12. Due to the excessive infusion of normal saline.
13. Hyperventilation.

Decreased level of Blood Chloride (Cl^–) (Hypochloremia):

1. excessive sweating.
2. Prolonged vomiting.
3. Gastric suction.
4. Salt losing nephritis.
5. Addisonian crises.
6. Metabolic acidosis is associated with increased organic anions.
7. Aldosteronism.
8. Respiratory acidosis.
9. Water intoxication.
10. Diuretic therapy.
11. Hypokalemia.
12. Burn
13. Overhydration.

Serum electrolytes in various conditions:

Acidosis and alkalosis:

Critical values of chloride in serum or plasma are:

• High value = >115 meq/L.
• Low value = <80 meq/L.

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