Hypo/Hypernatraemia

Question 1

What are some causes of hypernatraemia?

Answer 1

1. Hypovolemic
   
   • Dehydration.
   • Water loss - diarrhoea, vomiting, burns.
2. Euvolaemic - DI
3. Hypervolemic
   
   • Hypertonic fluid excess.
   • Conn’s syndrome - K raised, HTN, metabolic alkalosis.
   • Cushings.
   • Salt poisoning.

Question 2

What are the causes of Hyponatraemia?

Answer 2

1. Hypervolaemic
   
   • FAILURES (kidney, liver, heart)
2. Euvolemic - SIADH, Severe Hypothyroidism, Glucocorticoid insufficiency
3. Hypovolemic
   
   • Urinary sodium loss - Addison’s disease, Renal failure, Diuretics.
   • No Urinary sodium loss - D&V, Burns, CF, Small bowel obstruction.

Question 3

What are some of the potential non-pharmacological causes of SIADH?

Answer 3

• Brain damage
  
  • Meningitis/Encephalitis/abscess, SAH, Subdural Haemorrhage, Stroke.
• Malignancy
  
  • Small cell lung cancer, Pancreas and prostate cancer.
• Infections
  
  • TB, Pneumonia
• Drugs (See other card)
• Endocrine- Hypothyroidism
• Other - Porphyrias, Positive end-expiratory pressure (PEEP)

Question 4

What are some of the pharmacological causes of the release of ADH/Vasopression (SIADH and thus hyponatraemia)

Answer 4

• Diuretics (Thiazides especially)
• Antipsyhotics - haloperidol
• Antidepressants - SSRI, TCA
• Sulfonylureas
• Carbamazepine
• Morphine
• NSAIDs

Question 5

When starting SSRIs, when does ADH usually occur?

Answer 5

Usually within the first few weeks.

It then stops within 2 weeks of stopping.

If someone is elderly, is on diuretics and an SSRI is started then there is greater chance that they will develop hyponatraemia.