Hypochloraemia
April 24th, 2019
Overview
Hypochloraemia rarely exists on its own, and is usually found in the presence of hyponatraemia (due to salt depletion or dilution) or metabolic alkalosis. Hypochloraemia can also occur in the setting of renal compensation for respiratory acidosis.
Aetiology
Causes of Hypochloraemia
Salt Loss
- Extrarenal - vomiting, diarrhoea, 3rd spacing
- Renal - loop or thiazide diuretic abuse, Addison's, renal tubular acidosis
Dilution
- Osmotic shift - hyperglycaemia, mannitol
- Excess water intake - primary polydipsia, beer potomania
- Antidiuresis - SIADH, hypothyroidism, ACTH deficiency
- Fluid overload - heart failure, cirrhosis, nephrotic syndrome, renal failure
Metabolic Alkalosis
- GI acid loss - vomiting, NG aspirates, gastric fistula
- Renal acid loss - diuretics, Cushings, Conns, steroids
- Systemic bicarbonate excess - massive transfusion, dialysis
Compensation for Respiratory Acidosis
- Hypoventilation - drugs, obstructive sleep apnoea, neuromuscular disorders
- Dead space ventilation - emphysema
Approach
Determine whether the patient is hyponatraemic or has an acid-base abnormality, and then investigate further depending on the result.
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