BASICS
- Chloride is a major anion in the extracellular fluid
- Serum chloride concentrations may increase and decrease in proportion to changes in serum sodium concentrations
- Alterations in serum chloride concentrations not proportional to changes in serum sodium concentrations usually relate to acid–base abnormalities
- Serum chloride concentrations tend to vary inversely with serum bicarbonate concentrations
- Dependent on the underlying cause
- If severe and acute hyponatremia, lethargy, blindness, seizures, tremors, and abnormal gait are possible
- If related to an acid–base abnormality, the respiratory rate may be affected. If there is alkalemia, this may cause ionized hypocalcemia and synchronous diaphragmatic flutter
Proportionate Decreases in Sodium and Chloride
- Third spacing—when fluid accumulates in body spaces (e.g. abdominal and thoracic cavities, GI tract); ruptured urinary bladder in foals, abdominal effusions associated with colic, colitis, and peritonitis
- Iatrogenic—orally administered hypotonic fluids or excessive IV administration of 5% dextrose solution
- Inappropriate water retention caused by heart failure, hepatic fibrosis, severe hypoproteinemia, or syndrome of inappropriate antidiuretic hormone secretion
Disproportionate Decreases in Sodium and Chloride
- Renal disease
- Diarrhea and diseases causing fluid sequestration in the GI tract
- Prolonged diuresis or glucosuria may result in medullary washout and subsequent hyponatremia, hypochloremia, and metabolic alkalosis
- Adrenal insufficiency
- Primary metabolic alkalosis—serum chloride concentration decreases in compensation for increased serum bicarbonate concentration. Metabolic alkalosis may result from excessive sweating. Equine sweat contains a proportionally higher concentration of chloride than sodium; enhanced renal bicarbonate reabsorption occurs in compensation for chloride loss
- Compensatory response to respiratory acidosis—serum bicarbonate concentration increases in compensation for respiratory acidosis; serum chloride concentration decreases to maintain electroneutrality
- Metabolic acidosis with increased AG is often associated with colic because of increased concentrations of other anions (e.g. l-lactate) that maintain electroneutrality
- Furosemide—results in disproportionate loss of chloride in the thick ascending loop of Henle
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS