Common electrolyte disorders in primary care

1. Common electrolyte disorders in primary care Steve Hyer

2. ELECTROLYTES

3. Approach • History including drugs • Examination including fluid status, blood pressure • Screening tests • Confirmatory tests

4. Thinking about electrolytes Excess/reduced intake Redistribution Excess/reduced Loss

5. Is hyponatraemia important? 3 reasons…… • The wrong treatment can be disastrous • Rapid correction can be disastrous • Acute severe hypoNa associated with increased mortality T1: Low density T2: High density

6. Sodium Potassium Calcium Scope

7. Case 1 • 69y FNa 121 • Previously Na 139 • Started bendro 10d previously • Stopped bendro: Na 134 10d later. Diagnosis:Thiazide-induced hyponatraemia

8. Case 2 • 88y M • Acutely unwell with sodium 120 mmol/l and signs of pleural effusion. • Chest CT scan showed extensive inoperable bronchial carcinoma. . Diagnosis:SIADH associated with carcinoma bronchus

9. Case 3 • 83y F • Na 126–129 mmol/l following AP resection and ileostomy. • Urine: maximal sodium conservation. • Na normalised by reversal of ileostomy . Diagnosis:Salt and water loss through high flow stoma

10. Case 4 • 56y M • 10d diarrhoea and vomiting. • Na 108 mmol/l K 5.5 • Subsequent investigations confirmed Addison’s disease. . Diagnosis:Hyponatraemia due to adrenal insufficiency

11. 2 important hormones….

14. No aldosterone! (Adrenal insufficiency) ACE-inhibitors effectively lead to low aldosterone; can cause hypoNa

15. Diagnosis adrenal insufficiency SYNACTHEN TEST

17. Enhanced ADH release • Tumours releasing ADH eg Ca bronchus • CNS disorders affecting hypothalamus eg SAH • Pain especially thoracic • Nausea • Opiates, SSRIs, CBZP • Atypical pneumonia V2 receptors Dilutional hyponatramia

18. One important bit of the kidney….

19. Distal convoluted tubule This is where the aldosterone works • Drugs • Renal tubular acidosis • Chronic pyelonephritis

20. Excess water intake with low solutes

21. Low solute intake: Fun runners • Drinking fluids every mile • Gain weight after run! • Drink 3 litres + in a run of 1-2 hrs • Severe hyponatraemia and even death Non elite runner

22. Low solute intake: Beer potomania Beer • Very low sodium/ potassium • Maximum 4-5 litres of electrolye free water excretable per day • In absence of solute, >5L beer; severe hypoNa Tea + toast old ladies

23. Primary polydipsia • Low osmotic threshold to feel thirsty • Unable to suppress thirst • Exaggerated thirst Hyponatraemia + polydipsia + polyuria

24. Diagnosis……

25. Clinical symptoms

26. Step 1: Assess Volume status Mucosal membranes, tongue, skin turgor, urine output

27. Step 2: CLASSIFY Hyper-volaemic Normo-volaemic Hypo-volaemic Weight: Down OK Up

28. Step 3: Evaluate: Clinical

29. Step 4: Evaluate: Laboratory Conserving sodium Losing sodium in urine

30. Management SIADH • Underlying cause • Fluid restrict (0.5-1L/d) • May take days to come down • Maintain Na intake • (Demeclocycline-causes NDI) • VAPTANS (e.g.Tolvaptan) V2 blocker

31. Tolvaptan • Oral agent • Currently only in secondary care for chronic SIADH • Expensive but could reduce hospital stay • Especially where fluid restriction poorly tolerated • C/I Hypovolaemic hypoNa • ?long term

32. Secondary care Special tests • Hypertonic saline test • Water loading tests • Measurement of AVP • Hypertonic saline infusions –Na rise not >10mmol/d • Scans, etc DDI: Dipsogenic DI

33. Summary: Hyponatramia • Multitude of causes • Many patients with chronic mild hyponatraemia have adapted and apparently very well- may decompensate in acute illness • First do no harm!

35. History Thirst/ Polyuria No symptoms Drugs Examination Dehydrated Excessive water loss Hypernatraemia Na>145 Think diabetes insipidus

36. Algorithm Na Loss of water Loss of water

37. Hypokalaemia History • Diarrhoea, vomiting • No symptoms • Drugs eg Ventolin, diuretics, insulin Examination • Fluid status • Blood pressure Think diuretics

38. Cola drink hypokalaemia • Sugar++++ • Caffeine +++ • At least 2 litres/day

39. Hypertension + low K+ • Think Conn (Hyper-aldosteronism) • Think Cushing • Think renal artery stenosis Renin: Aldo ratio

40. Algorithm K Gut loss Renal loss

41. History Renal No symptoms Drugs eg ACE-I, spiro, amiloride Examination Addisons Renal Hyperkalaemia K>5.0 Think renal failure Don’t forget haemolysed samples, old samples

42. Algorithm Output Input Don’t forget Addison

43. Hypercalcaemia Ca>2.6 • Mild hypercalcaemia (Ca <3mmol) • Mostly due to primary hyperparathyroidism • Usually asymptomatic • Diagnosis: Ca blood/ urine + PTH

44. Recommending PTH-ectomy • Patient fit for surgery • Significantly reduced BMD on DEXA scan • Reduced renal function (eGFR) • Ca>2.85 • History of stones • Increased Ca excretion Frail elderly: consider bisphosphonate infusion

45. Moderate-severe Ca • Consider malignancy esp older patient • Myeloma • Sarcoidosis • Thyrotoxicosis • FHH • Drugs Bisphosphonates

46. Malignant hypercalcaemia Tumour mets Non-metastatic (PTH-RP)

47. Algorithm

48. Low calcium Ca <2.2mmol • Usually Vitamin D deficiency (30% elderly, 90% Asians?) • May be Chronic renal failure • HypoPTH • PseudohypoPTH • (Low Mg) Lack of sun Phytate in chipatis Housebound

49. High Ca High PTH Low Ca High PTH High Ca Low PTH Low Ca Low PTH

50. Assessment Ca History • Diet/ diarrhoea/ mal-absorption • Thyroid surgery • Drugs eg phenytoin Examination • Tetany, Chvostek • Renal Investigations • Ca/P/ Alk P’ase/ Vit D/ PTH