SIADH = Syndrome of inappropriate antidiuretic hormone secretion
Important cause of HYPOnatraemia
Diagnosis requires
- Presence of
- HYPOnatraemia
- Euvolaemia (normovolemia)
- High urinary sodium (>20 mmol/L)
- Urine osmolality > plasma osmolality
- Serum osmolality <280 mmol/kg (hypotonic HYPOnatremia)
- Urine osmolality >500mmol/kg (inappropriately concentrated)
- Absence of
- Abnormal renal, cardiac, thyroid, adrenal hepatic function
- Hypervolaemia (oedema)
- NOT on a diuretic
Cause
- Malignancy
- Small cell lung, pancreas, prostate, leukaemia, cervical
- Central Nervous System (CNS)
- Tumour
- Trauma (Head injury, SAH, SDH)
- Infection (encephalitis, abscess)
- Vascular (CVA, aneurysm, vasculitis)
- Other (GBS, MS, DT)
- Respiratory
- Tumour
- Infection (aspergillosis, pneumonia, abscess)
- COPD, CF
- Drugs
- Opiates
- Psychotropic (TCA, MAOI, SSRI)
- Cytotoxic, chemotherapeutic
Correction
- Corrected with water restriction 500-1000ml/day
- Does not respond to Na replacement
References and Links
- CCC – Hypernatraemia
- CCC – Hypernatraemia Mind map (PDF)
- CCC – Hyponatraemia
- CCC – Hyponatraemia Mind map (PDF)
- CCC – Hyponatraemia Interpretation (PNG)
- CCC – SIADH – SIADH DDx
- CCC – Diabetes Insipidus Central – Diabetes Insipidus DDx
- Case – Exercise-associated Hyponatremia
- Case – Seizures, hyponatremia and ADH
Critical Care
Compendium
