SIADH Flashcards
Define SIADH.
The syndrome of inappropriate antidiuretic hormone (SIADH) is characterised by hypotonic hyponatraemia, concentrated urine, and a euvolemic state.
Explain the aetiology/risk factors of SIADH.
Age >50 years
Pulmonary conditions (e.g., pneumonia)
Nursing home residence
Malignancy
Medicine associated with SIADH induction
Central nervous system (CNS) disorder
Summarise the epidemiology of SIADH.
A report of 184 episodes of severe hyponatraemia (reported as ≤120 mmol/L [≤120 mEq/L]) in hospitals across the US and UK found that in 21% of people the condition was of acute duration and in 79% it was of chronic duration.
Recognise the presenting symptoms of SIADH. Recognise the signs of SIADH on physical examination.
Absence of hypovolaemia
Absence of hypervolaemia
Absence of signs of adrenal insufficiency or hypothyroidism
Nausea/vomiting
Altered mental status
Headache
Seizure
Coma
Identify appropriate investigations for SIADH and interpret the results.
Serum sodium
Serum osmolality
Serum urea
Urine osmolality
Urine sodium
Generate a management plan for SIADH.
Fluid restriction
Furosemide
Vaptans
Identify the possible complications of SIADH and its management.
Central pontine myelinolysis (CPM or osmotic demyelination syndrome)
What is central pontine myelinolysis (CPM or osmotic demyelination syndrome)?
The brain adapts slowly to hyponatraemia by secretion of intracellular solutes such as sodium and potassium initially, followed by amino acids and myoinositol (organic osmolytes). Overcorrection of hyponatraemia can subject solute-poor cerebral cells to shrinkage and CPM.
Summarise the prognosis for patients with SIADH.
If the underlying cause is found and treated successfully, SIADH typically resolves. If the underlying condition persists, SIADH is difficult to manage, secondary to difficulty complying with necessary fluid restriction or medicines.
