SIADH Flashcards
ADH function
Stimulates water reabsorption from the collecting ducts in the kidneys
SIADH
Condition where there is inappropriately large amounts of ADH
Excessive ADH means water dilutes sodium in the blood
Urine becomes more concentrated as less water excreted by kidneys
SIADH urine
More concentrated as less water excreted
High urine osmolality and high urine sodium
Symptoms
Headache
Fatigue
Muscle cramps and aches
Confusion
Severe hyponatraemia can cause seizures and reduced consciousness
Malignant causes
Small cell lung cancer
Pancreatic cancer
Prostate cancer
Neurological causes
Stroke
SAH
Subdural haemorrhage
Meningitis/ encephalitis/ abscess
Infective causes
TB
Pneumonia
Drug causes
Sulphonylureas
SSRIs/ TCAs
Carbamazepine
Vinctristine
Cyclophosphomaide
Other causes
Positive end-expiratory pressure
Porphyrias
Initial diagnosis
Clinical evaluation shows euvolaemia
U+Es show hyponatraeamia
Urine sodium and osmolality high
Management
Establish and treat cause
Correct sodium slowly to prevent central pontine myelinolysis
Fluid restriction
Tolvaptan (ADH receptor blocker)
Demeclocylcine (inhibits ADH)
Central pontine myelonlysis
When rapid treatment, blood sodium levels rise and water rapidly shifts out of brain cells into blood
Patient first encephalopathic and confused; may have headache, nausea and vomiting
Next demyelination of neurones
Presents as spastic quadriparesis, pseudobulbar palsy and cognitive behavioural changes
