Syndrome of inappropriate antidiuretic hormone

1. Syndrome of inappropriate antidiuretic hormone
Etiologies
• CNS disturbance (eg, stroke, hemorrhage, trauma)
• Medications (eg, carbamazepine, SSRIs, NSAIDs)
• Lung disease (eg, pneumonia)
• Ectopic ADH secretion (eg, small cell lung cancer)
• Pain &/or nausea
Clinical
features
• Mild/moderate hyponatremia: nausea, forgetfulness
• Severe hyponatremia: seizures, coma
• Euvolemia (eg, moist mucous membranes, no edema, no JVD)
Laboratory
findings
• Hyponatremia
• Serum osmolality <275 mOsm/kg H2O (hypotonic)
• Urine osmolality >100 mOsm/kg H2O
• Urine sodium >40 mEq/L
Management
• Fluid restriction ± salt tablets
• Hypertonic (3%) saline for severe hyponatremia