Chloride

Normal: 96 to 106 mEq/L (96 to 106 mmol/L)

Physiology:

Chloride is the most abundant extracellular anion; however its intracellular concentration is small.  It balances out positive charges in the extracellular fluid and by passively following sodium, helps to maintain osmolality.  It plays a role in the ability of blood to carry CO2 to the lungs and is important in potassium conservation.  Like sodium, a change in the serum chloride concentration does not necessarily reflect a change in total body content.

Empiric daily requirement

Adults:  As needed to balance acid/base (80 to 100 mEq/day)

Infants/children:  As needed to balance acid/base (2 to 4 mEq/kg/day)

Hypochloremia: levels below 96 mEq/L

Causes:

Assessment:

Signs and symptoms are due to the underlying fluid status or acid-base balance rather than to the chloride itself.

Labs:

Serum chloride below 96 mEq/L.  In hypochloremic metabolic alkalosis the arterial pH is greater than 7.45 and the serum bicarbonate exceeds 28 mEq/L .

Correction:  

Treat underlying causes of excess chloride and acid loss, administer H-2 blockers to decrease acid loss.  Avoid all lactate-containing IV solutions  (e.g., Ringer's lactate) and administer IV saline.

TPN correction:

Decrease acetate intake by administering chloride salts until the alkalosis resolves and the serum chloride level returns to normal.

Hyperchloremia: levels above 106 mEq/L

Causes:

Assessment:

Signs and symptoms are due to the underlying fluid status or acid-base balance rather than to the chloride itself.

Labs:

Serum chloride above 106 mEq/L.  In hyperchloremic metabolic acidosis arterial pH is less than 7.35 and a serum bicarbonate is below 22 mEq/L .

Correction:  

Treat the underlying cause, restrict salt intake.

TPN correction:

Reduce chloride intake by administering acetate salts until the acidosis resolves and the serum chloride level returns to normal.