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Managing Hyponatraemia: Case Studies and Treatment Strategies

Explore the definition, pathogenesis, and epidemiology of hyponatraemia through two detailed case studies. Learn about the causes, severity, investigations, and management approaches for acute and chronic severe hyponatraemia, including essential criteria for SIADH. Discover the physiological aspects and common etiologies associated with this condition.

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Managing Hyponatraemia: Case Studies and Treatment Strategies

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  1. SpR Topic:Hyponatraemia Jamilla Hussain ST3 April 2012 St. Catherine’s Hospice

  2. AIMS • 2 Case study • Definition • Pathogenesis • Epidemiology

  3. Case 1: SM • 39 year old female • A+E: fatigue, headache, nausea and vomiting, and profound weight loss ~ 1/12 • OE: nil acute • Ix: Na 115, CXR: RUL mass, enlarged mediastinum • Seen by KC - Admitted

  4. CLINICAL ASSESSMENT

  5. Hx and Examination • VOLUME STATUS • CAUSES • SEVERITY

  6. Volstatus:Causes

  7. Severity

  8. Investigations-

  9. Plasma Osmolality < 280

  10. Essential Criteria for SIADH • Plasma Na<135mmol/l • Urine osmolalilty >100mOsm/kg • Urine Na >20 mmol/l • Euvolaemic • Exclusion of glucocorticoiddefficiency • Normal salt intake • Euvolaemic, urine Na>20, repeat Na 113

  11. Management

  12. Management of acute hyponatraemia + severe symptoms • Acute <48 hours • Fall >0.5mmol/l per day • Mortality 5-8% • IV hypertonic saline solution • 1.8% Saline = 0.3mmol/l Na • 1ml/kg body weight/hour • Aim 0.5mmol/l per hour correction • No more than 4-6 mmol/12 hr, stop >120mmol/l

  13. Central pontinemyelinosis • Balance risk of mortality with low Na with risk of irreversible myelinosis • 1-2 days post correction • Coma, confusion • Quadraparesis • CN defects, bulbar palsy (pons) • Cerebral irritation by low Na can produce irreversible brain damage, therefore hypertonic solution is life saving/brain preserving • 2 hourly assessment of Na • Worse if chronic/alcoholic

  14. SM • Infusion on ward whilst waiting transfer • Deteriorated rapidly on ward • Spoke to consultant • Opted for supportive care + uninterrupted time with children

  15. Definition • Na < 136mmol/l • SIAD more appropriate (15% no vasopressin) • Concentrated urine + hypo-osmolar plasma suggest abnormal free water excretion

  16. Physiology • Vasopressin gene on Ch. 20 • Peptide produce Arginine vasopressin (AVP) + vasopressin-specific neurophysin II (NP II) • HypothalamusPost. PituitaryAVP + NPII • 3 AVP receptions, V2 on renal CD • AVP binds V2c-AMPinserts AQP2 • Acquaporin water channels into apical plasma membrane CD • Allow passage of free water but not ions

  17. Epidemiology • Stimulation of HPA • Distal nephrons • Paraneoplastic -tumour secretes ectopic AVP - OR vasopressin-like peptide

  18. Epidemiology • Commonest SCLC, carcinoid • Pancreatic, oesophageal, prostatic, haematological • 523 SCLC- 9%SIAD • 32% ↑ AVP, 53% renal handling abnormal • Prognosis and response same +/- SIAD • Incomplete restoration of renal handling

  19. Other causes • Drugs: Opiates, TCA, Haloperidol, AED, SSRI, NSAIDS Vincristine, cyclophosphamide • Chest: Pneumonia, TB, abscess • CNS: Meningitis, CVA, Tumour/mets • Post operative, NV, pain

  20. Case 2 JE • 67, Ca Prostate 2009 bone/liver mets -Previous TURP, RDx, Bicalutamide, stilbeosterol, zoladex -Neuroendocrine tumour-small cell -Etoposide and carboplatin and dex -Admitted to SCH prior to 1st cycle

  21. Clinical assessment • Nausea • Poor appetite • Dizziness • P=100, JVP not visible, grossly oedematous legs/scrotum • Meds: codanthramer, ondansetron, dex, domperidone

  22. Investigations

  23. Management

  24. Management of chronic severe ↓Na • Fluid restrictions -500ml IP -several days • Distal nephron inhibitors -Demeclocycline (tetracycline) -Nephrogenic DI-stops cAMP production -900 to1200mg per day, takes 3 days - SE: GI and photosensitive rash

  25. Chronic severe hyponatraemia • Urea -osmotic diuretic, increases free water excretion -oral 30g in orange juice -no need for fluid restriction • Vasopressin analogues VAPTANS -promote sustained aquaresis -Tolvaptan, selective V2 -check Na 8hrs after 1st dose then daily

  26. Mixed picture • Usually have other contributing factors -Vomiting -CCF -Liver failure -Renal impairment -Diuretics -Hyperglycaemia -need to consider other additional causes and manage

  27. Mild-moderate symptoms Na>125 • Acute: Tx cause and fluid restrict • Chronic: Tx cause and Vaptans • ASYMPTOMATIC NA>125 -Tx cause and fluid restrict

  28. Summary • Clinical Assessment: FLUID STATUS/ CAUSE/SEVERITY • Ix: UEs, Paired osm, urine Na, TFTs, (synacthen) LFTs, lipids and glucose • Tx: Acute vs. Chronic Severe vs. mild-moderate vs. asymptomatic • ? Mixed picture

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