Hyponatraemia (Case Presentation)


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A case of severe hyponatraemia with a discussion of sodium and water balance

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Hyponatraemia (Case Presentation)

  1. 1. Dazed and Confused
  2. 2. History <ul><li>Mrs AA, 66 yo ♀ from home w husband </li></ul><ul><li>PHx hypertension, hyperlipidaemia </li></ul><ul><li>1/52 ago dx with UTI. Allergy: penicillin – given Bactrim by LMO </li></ul><ul><li>4/7 vomiting, diarrhoea, anorexia, increasing confusion </li></ul><ul><li>2/7 Na 110, asked to present to ED </li></ul><ul><li>Presented to MMC ED with severe confusion, lethargy, anorexia. No seizures/fits/neurological symptoms. </li></ul>
  3. 3. Drugs <ul><li>Telmisartan (A2RB) </li></ul><ul><li>Atorvastatin </li></ul>
  4. 4. Examination <ul><li>General: Confused +++ Not oriented to time, place or person. GCS 14. Very dry mucous membranes, clinically volume deplete. Pink, perfused. </li></ul><ul><li>Chest: JVP 0 cm, S1+S2+0, Scattered R basal crackles </li></ul><ul><li>Abdo: Soft, tender palpable bladder, nil organomegaly </li></ul><ul><li>Neuro: 5/5 power bilat, brisk reflexes, downgoing plantars, normal sensation. Nil seizure activity. </li></ul>
  5. 5. Investigations <ul><li>Urgent VBG: Na 98 , K 3.7, Gluc 10.5 pH 7.50, pCO2 25, HCO3 20 </li></ul><ul><li>Serum Osmolality: 211 (~twice serum Na + K ie 103) </li></ul><ul><li>Urine Osmolality: 263 </li></ul><ul><li>Urine Na: 51 </li></ul><ul><li>Urine K: 28 </li></ul><ul><li>eGFR >60 </li></ul><ul><li>CXR: NAD </li></ul><ul><li>MSU MC&S: Enterococcus spp sens amox, nitrofurantoin </li></ul><ul><li>UEC in 11/2007: Na 139, K 4.7 </li></ul>
  6. 6. Management <ul><li>Admit ICU </li></ul><ul><li>Monitor for seizures </li></ul><ul><li>Hourly VBG </li></ul><ul><li>After extensive discussion w. ICU consultant- decision to commence N Saline + 10mmol KCl for volume depletion and hypokalaemia </li></ul><ul><li>Aim for 8mmol increase in serum sodium per day only – risk of central pontine myelinolysis </li></ul><ul><li>H20 restriction – 500mL orally only per day </li></ul>
  7. 7. Progress <ul><li>Increase in serum sodium to 111 (13mmol) after 11 hrs! </li></ul><ul><li>Saline ceased, H20 restriction continued </li></ul><ul><li>Likely secondary to drop in ADH once hypovolaemia corrected </li></ul><ul><li>Fortunately nil neurological changes, seizures, paralysis! </li></ul><ul><li>Continuing hypokalaemia, hypocalcaemia, hypophosphataemia (replaced IV via CVC) </li></ul><ul><li>Hypokalaemia spontaneously resolved. Calcium and phosphate remained low </li></ul>
  8. 8. Investigations (cont.) Saline Ceased Saline commenced Sodium 127
  9. 9. Investigations (cont.) <ul><li>Cortisol: 1022 (N) </li></ul><ul><li>TSH: 0.37 </li></ul><ul><li>FT4: 19.5 </li></ul><ul><li>Vit D: 25 </li></ul><ul><li>PTH: 3.9 (N) </li></ul><ul><li>MSU MC&S: Enterococcus spp sens amox, nitrofurantoin </li></ul>Subclinical Hyperthyroidism
  10. 10. Progress (cont.) <ul><li>Day 3: Discharge from ICU (Na 119) </li></ul><ul><li>Day 4-8: Confusion and unsteady gait slowly resolved with increase in serum Na to 132 </li></ul><ul><li>Day 8 (day of discharge): Patient stated she felt much better, had been confused ++ for 2 months with husband caring for her at home. Used to drink >3-4L/day at home because it was “a good thing for health” but understands fluid restriction and need for adherence. </li></ul><ul><li>Patient discharged with follow up UEC CMP 1/9 and 4/9 with LMO – for FFIx if drop in sodium </li></ul>
  11. 11. Bad pun of the week <ul><li>“ Mrs AA and how she decided to stop drinking !!” </li></ul>
  12. 12. Differential Diagnosis <ul><li>Acute volume depletion only in setting of UTI, vomiting, diarrhoea </li></ul><ul><ul><li>However: Na 98!! CNS adaptation occurs over 2-3 days. Marked decrease in Na over 1-2 days assoc with cerebral oedema & seizures. Mrs AA relatively asymptomatic (exc confusion) </li></ul></ul><ul><li>Acute on chronic hyponatraemia </li></ul><ul><ul><li>Perhaps slow decrease in Na ?Primary Polydipsia ?SIADH acutely worsened by volume depletion during illness </li></ul></ul>
  13. 13. Differential Diagnosis <ul><li>If chronic hyponatraemia </li></ul><ul><ul><li>Primary polydipsia- high water intake reported by patient, low urinary sodium when pt volume replete. However: normal renal function- to overwhelm kidney ability to clear H2O r/q intake >10L/day!! </li></ul></ul><ul><ul><li>SIADH- normal urinary osmolality even when serum sodium 127. However: borderline low urine sodium </li></ul></ul>Diagnosis Unclear
  14. 14. Salt and Water A potentially confusing topic!
  15. 15. Measuring the sodium <ul><li>Blood gas machine = direct measurement (new) </li></ul><ul><li>For UEC however, sample centrifuged, lipid and protein component removed </li></ul><ul><li>Thus if grossly raised lipids (severe hyperlipidaemia) or protein (myeloma) – Na appears low “pseudohyponatraemia” </li></ul><ul><li>Result should be verified </li></ul>
  16. 16. Distribution of fluid
  17. 17. Control of Fluid Balance and Osmolality
  18. 18. Effective Volume <ul><li>An idea about tissue perfusion and useful IV volume </li></ul><ul><li>Indirect measures – MAP, JVP, renal artery pressure </li></ul><ul><li>Detected by body in several places – carotid baroreceptors </li></ul><ul><li>Low in hypovolaemia </li></ul><ul><li>Low in CCF – poor CO </li></ul><ul><li>Low in CLD – hyperdynamic circulation, ascites, AV fistulae </li></ul><ul><li>Low in nephrotic sx – ascites </li></ul>
  19. 19. Urine Output <ul><li>Effective Volume  R-A-A axis, sympathetic drive  Total salt & osmolar excretion/day </li></ul><ul><li>LowADH  Urine osmolality </li></ul>
  20. 20. Hyponatraemia <ul><li>Inability to produce dilute urine </li></ul><ul><li>Causes: </li></ul><ul><ul><li>Interference of renal ability to dilute urine </li></ul></ul><ul><ul><li>Low effective volume </li></ul></ul><ul><ul><li>SIADH </li></ul></ul><ul><ul><li>Endocrine: Addison’s, hypothyroidism, DKA </li></ul></ul>
  21. 21. Causes of hyponatraemia <ul><li>Old age </li></ul><ul><li>Post-surgical </li></ul><ul><li>Diuretics – thiazides, spironolactone, lasix </li></ul><ul><li>CCF, CLD, CRF, Nephrotic syndrome </li></ul><ul><li>Volume depletion and H2O overload </li></ul><ul><li>Drugs – anticonvulsants, chemo, Ecstasy </li></ul><ul><li>Endo: DKA, Hypothyroidism, Addison’s </li></ul><ul><li>Neuro – tumour, bleed, infection, psychosis </li></ul><ul><li>Paraneoplastic SIADH – esp. Lung </li></ul><ul><li>Exogenous vasopressin, iatrogenic ie fluids </li></ul>
  22. 22. Management - Investigation <ul><li>Is this real? </li></ul><ul><ul><li>Verify result – (done automatically at MMC) or with VBG (direct) </li></ul></ul><ul><ul><li>If VBG Na normal and/or high osmolar gap investigate for pseudohyponatraemia instead- lipids, myeloma screen! </li></ul></ul><ul><li>What other osmotes are there? </li></ul><ul><ul><li>UEC, BSL, Plasma osmo </li></ul></ul><ul><ul><ul><li>Check for urea, glucose as additional osmotes. </li></ul></ul></ul><ul><ul><ul><li>DKA should not be missed! </li></ul></ul></ul><ul><ul><ul><li>Posm ~ 2x Na – adjust if high urea, glucose. Work out osmolar gap </li></ul></ul></ul><ul><li>Is the urine appropriate? </li></ul><ul><ul><li>Measure urine output, urine osmo (this incl urea) and sodium. potassium now and post FR/sodium correction </li></ul></ul>
  23. 23. Management – History <ul><li>History of fits/seizures! </li></ul><ul><li>Chronicity of symptoms, any major fluid losses, any oedema, water intake, comorbidities </li></ul><ul><li>Drugs </li></ul><ul><li>Comorbidities </li></ul><ul><li>GCS/MSE/Orientation </li></ul>
  24. 24. Management – Examination <ul><li>Assess fluid state – hyper/hypo/normovolaemia </li></ul><ul><li>Neuro exam </li></ul><ul><li>Other examinations PRN </li></ul>
  25. 25. Management – what next? <ul><li>If there are fits/coma all bets are off- pt may require hypertonic saline and ICU admission </li></ul><ul><li>Hypovolaemia: </li></ul><ul><ul><li>N. Saline w. close monitoring of serum sodium </li></ul></ul><ul><ul><li>Restrict free water </li></ul></ul><ul><li>Fluid Overload: </li></ul><ul><ul><li>Fluid and free water restriction ± diuresis (lasix) </li></ul></ul><ul><li>Normovolaemic: </li></ul><ul><ul><li>Cease offending drugs </li></ul></ul><ul><ul><li>Fluid and free water restriction </li></ul></ul>
  26. 26. Central Pontine Myelinolysis <ul><li>Fast correction of sodium/24-48hrs </li></ul><ul><li>Unclear aetiology </li></ul><ul><li>Poor relationship with speed of correction ?assoc with correction over 1-2 days rather than hourly </li></ul><ul><li>Destruction of myelin sheaths in pons </li></ul><ul><li>Severe paralysis, locked-in syndrome </li></ul><ul><li>Try to avoid correction >10mmol/day – close monitoring of UEC essential </li></ul>
  27. 27. Further Investigation <ul><li>Repeat UEC – monitor Na, K, renal function </li></ul><ul><li>Cortisol, TSH </li></ul><ul><li>Repeat urine osmo, Na and K post FR/correction of serum Na to see if it corrects (and how quickly) </li></ul><ul><li>Consider: CT brain, CT chest/abdo/pelvis </li></ul>
  28. 28. Between the ocean and the desert…