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12.12.04 Sodium

Classification

  Hyponatraemia Hypernatraemia
Hypervolaemia
  • Total body sodium is HIGH
  • Heart failure
    • Triple diuretic therapy => Natriuresis
  • Liver failure
  • Treat with FLUID RESTRICTION
  •  Doctor's fault
    • Too much saline
  • Treat with dialysis
Euvolaemia
  •  SIADH
    • => Mild hypervolaemia
    • Activates natriuresis => Euvolaemia
    • Low serum Osm, High urine Osm
    • SAME PICTURE as in heart failure, diarrhoea
    • => MUST check urine [Na] too
    • MUST exclude the 4 failures
      • Heart, kidney, liver, adrenal
  • Causes of SIADH
    • Head
      • Abscess
      • Meningitis
      • Tumour
    • Chest
      • SCLC
      • Pneumonia
      • Abscess
      • TB
      • Empyaema
    • Drugs ("The anti's")
      • -psychotics
      • -convulsants (beware of causing more fits!)
      • -depressants
      • -diuretics
  • Treatment of SIADH
    • Fluid restriction
    • Vasopressin desensitisors
      • Lithium
      • Domeclocycline
    • Vaptans (incredibly expensive)
  •  Diabetes insipidus
    • Lithium
  • Treat with desmopressin
Hypovolaemia
  •  Thiazide diuretics
    • Hit the quality control
  • Burns
  • D+V
  • Endocrine
    • Addison's (unmasked by Hx of trauma?)
    • Diabetes (osmotic diuresis)
      • cf Pseudohyponatraemia
    • Cerebral salt wasting
  • Total body sodium is LOW
  • Therefore same causes as hypovolaemic hyponatraemia
    • Except Addison's


Central pontine myelinolysis
  • Affects CN III - VII
  • Characteristic feature is gaze palsies
    • Conjugate (complex) palsy
    • INO
  • Also:
    • Long tract signs (spasticity)
    • Reduced level of consciosuness
Marathons
  • Perfect storm:
    • Complete loss of glycogen
    • Rise in vasopressin
    • Hypotonic fluids
  • Treat with twice-normal saline

Notes
  • Vasopressin is a STRESS HORMONE
    • Hyponatraemia in marathons
    • Hyponatraemia with MDMA
  • Never give sodium or fluids together with diuretics
  • Never give hyperosmolar saline without consultant approval
  • Kidneys filter per day:
    • 180 L of fluid
    • 2 kg of NaCl
  • Correct sodium at no more than 8 mM per day
    • Use no more than 500 ml saline per day

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