Excessive amounts of Cl- are usually the result of administration of NaCl, volume depletion, or entities causing metabolic acidosis without a widened anion gap (see Chap, 21, "Acid-Base Disorders").
NaCl, KCl, or amino acid hydrochlorides readily dissociate and bind with bicarbonate, leading to metabolic acidosis. The effects of hyperchloremia are a result of volume depletion or acidosis. Since Na+ and Cl- travel together, high levels of serum Na + are associated with high levels of serum Cl-. Bicarbonate is inversely proportional to Cl-, so hyperchloremia is associated with non-widened-anion-gap metabolic acidosis. If Na + levels are normal in the face of elevated Cl-, one must think of KCl or amino acid hydrochloride administration (again leading to non-anion-gap acidosis). Finally, bromism, rarely seen today, may present with hyperchloremia, as Br- is factitiously measured as Cl- in hospital laboratories. A narrow anion gap will be an important clue in this latter diagnosis.
APPROACH Similar to hypochloremia, clinical conditions associated with hyperchloremia, are rarely considered from the perspective of the serum [Cl -]. Rather, the [Cl-] is used as a diagnostic adjunct. For example, in the setting of metabolic acidosis, an elevated [Cl -] will merely help confirm the acidosis type when it is also noted that the anion gap is not widened. Thus, rather than seeking the cause of the hyperchloremia, clinicians can approach the differential diagnosis from the perspective of the nonwidened metabolic acidosis (see C.h.a.p;.2.1., "Acid-Base Disorders"). Similarly, when [Cl-] is elevated in hypernatremic states, the differential diagnosis can be considered from the perspective of elevated [Na+] and the volume status of the patient (vide supra).
TREATMENT If there is excess administration of chloride or excessive losses of bicarbonate, this should be corrected. Hyperchloremia due to dehydration is best treated by slowly administering increased isotonic fluids with little or no chloride. However, if too much isotonic fluid is given too rapidly, seizures due to cerebral edema may develop.
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