Causes of hyponatremia

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 Hypovolemic hyponatremia:

Renal loss:

  • Diuretics
  • Ketonuria
  • Hypoadrenalism - mineralocorticoid deficiency 
  • Metabolic alkalosis 
  • Renal tubular acidosis
  • Protein-losing nephropathy 

Extrarenal loss:

  • Vomiting 
  • Diarrhoea 
  • Burn 
  • Pancreatitis 
  • Third space loss

Hypervolemia hyponatremia:

  • Congestive cardiac failure 
  • Cirrhosis 
  • Nephrotic syndrome 

Euvolemic hyponatremia:

↓ Plasma osmolarity:

  • SIADH
  • Renal failure 
  • Hypothyroidism 
  • Surgical stress/ Sympathetic stimulation 
  • Glucocorticoid deficiency
  • Drugs
    • ↑ ADH secretion - 
      • Barbiturate 
      • Opioid 
      • Hypoglycemic
      • SSRI
      • Antipsychotic 
      • Carbamazepine 
    • Potentiation of ADH - 
      • Paracetamol
      • NSAIDs
    • ADH analogue - 
      • Oxytocin
      • Vasopressin
      • Desmopressin 

Normal plasma osmolarity:

  • Pseudohyponatremia  


Reference: 
Smith and Aitkenhead's Textbook of Anaesthesia, 7th Edition
Stoelting's Anesthesia and Co-Existing Disease, 7th Edition 

Morgan & Mikhail's Clinical Anesthesiology, 6 Edition 

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