Definition & Etiology

Definition

– Serum sodium < 135 mmol/L
– Classified as mild (131-135), moderate (125-130), severe (<125)
– Acute: < 48 hours of development – Chronic: > 48 hours of development

Prevalence
– Most common electrolyte disturbance
– Common in the elderly
– Often an incidental finding

Etiology
Multifactorial:
– Heart failure
– CKD
– Nephrotic syndrome
– Medications: SSRIs, thiazide diuretics, ACE inhibitors
– SIADH
– Pseudohyponatremia
– Cerebral salt wasting
– Primary adrenal insufficiency
– Post-surgery
– Hypothyroidism
– Psychogenic polydips