Syndrome Of Inappropriate ADH secretion (SIADH) is hyponatraemia due to an increase in concentration of ADH inappropriate to the current osmotic or volume status. The differential diagnosis includes ADH analogues


  1. hypotonic hyponatraemia
  2. urine osmolality > plasma osmolality (<275mOsm/kg) (i.e. concentrated urine despite hypotonic blood)
  3. urinary Na+ > 20mmol/L
  4. normal renal, hepatic, cardiac, pituitary, adrenal and thyroid function
  5. euvolaemia (absence of hypotension, hypovolaemia, and oedema)
  6. correction by water restriction


Major Surgery

  • abdominal
  • thoracic
  • transsphenoidal pituitary surgery (6-7 days post op)

ADH production by tumours (Ectopic)

  • small cell bronchogenic carcinoma
  • adenocarcinoma of pancreas/duodenum
  • leukaemia
  • lymphoma
  • thymoma


  • antidepressants (e.g. SSRI, TCAs, MAOIs)
  • psychotropics (e.g. haloperidol, chlorpromazine), carbamazepine, Na+ valproate)
  • anaesthetic drugs (barbiturates, inhalational agents, oxytocin, opioids)
  • ADH analogues (vasopressin, DDAVP)
  • chemotherapy (e.g.Vinca alkaloids, Melphalan, Methotrexate and cyclophosphamide)
  • others (e.g. NSAIDs, amiodarone, ciprofloxacin, morphine, MDMA, proton pump inhibitors)

CNS Disorders

  • cerebral trauma
  • brain tumour (primary or metastases)
  • meningitis/encephalitis
  • brain abscess
  • SAH
  • acute intermittent porphyria
  • SLE

Hormone deficiency

  • hypothyroidism
  • adrenal insufficiency


  • Guillain-Barre Syndrome
  • HIV infection (early symptomatic or AIDS)
  • hereditary SIADH
  • giant cell arteritis
  • idiopathic (occult small cell or olfactory neuroblastoma)

Pulmonary Disorders

  • pneumonia (viral, fungal, bacterial)
  • TB
  • lung abscess


  • see hyponatraemia document
  • fluid restrict
  • incremental increase in Na+ if indicated to avoid central pontine myelinolysis
  • medications to decrease ADH secretion
    • Demeclocycline
    • Tolvaptan / Conivaptan

References and Links

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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