Disorders of electrolyte balance: an overview


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Disorders of electrolyte balance: an overview

  1. 1. Disorders of Electrolyte balance Souvik Maitra MD, DNB 1
  2. 2. Body water distribution
  3. 3. Electrolyte distribution
  4. 4. Disorders of water balance: Hyponatremia
  5. 5. Epidemiology 20% of critically ill patients 15% emergency admission 1-7% surgical patients
  6. 6. Classification Hypotonic Hypertonic Isotonic: pseudohyponatremia
  7. 7. Low extracellular volume: Renal loss (diuretics, Na loosing nephropathy), extra renal loss Normal extracellular volume SIADH, Adrenal insufficiency, Hypothyroidism Increased extracellular volume CHF, cirrhosis, nephrotic syndrome
  8. 8. Clinical features Moderately severe Nausea, Confusion, headache Severe symptoms Vomiting Cardio-respiratory distress Abnormal and deep somnolence, Seizures Coma (Glasgow Coma Scale <8) Hyponatremic encephalopathy
  9. 9. SIADH Essential criteria Effective serum osmolality <275 mOsm/kg Urine osmolality >100 mOsm/kg Clinical euvolaemia Urine sodium concentration >40 mmol/L with normal dietary salt and water intake Absence of adrenal, thyroid, pituitary or renal insufficiency No recent use of diuretic agents Supplemental criteria Serum uric acid <0.24 mmol/L (<4 mg/dL) Serum urea <3.6 mmol/L (<21.6 mg/dL) Failure to correct hyponatraemia after 0.9 % saline infusion Fractional sodium excretion >0.5 % Fractional urea excretion >55 % Fractional uric acid excretion >12 % Correction of hyponatraemia through fluid restriction
  10. 10. Management Target increase serum Na 0.5 mEq/l in one hour In severe symptomatic patients: Increase in serum Na 1- 2mEq/l/hr. Intravenous infusion of 3 % saline at 2ml/kg over 20 min and check Na after 4 hours. Target [Na] rise 5mEq/l over four hours Intensive Care Med 2014:40;320–331
  11. 11. If patient remains symptomatic despite increase in [Na] at 5mEq/l, consider increasing [Na] another 1mEq/l. Change in [Na]= Infusate [Na]- Serum [Na]/ TBW+1 Q J Med 2005;98:529–540
  12. 12. Vasopressin antagonists Indicated in hypotonic euvolemic hyponatremia
  13. 13. Hypernatremia Serum [Na]> 145mEq/l Always associated with hypertonicity Due to water deficit or [Na] gain
  14. 14. Mechanism Water loss Renal loss: osmotic diuresis, DI (central or nephrogenic) Extra renal: Diarrhoea (viral, osmotic) Primary Na gain Mineralocorticoid excess Iatrogenic
  15. 15. Clinical features CNS: Altered mental status, confusion, focal neurological deficit seizure coma Polyuria, thirst (DI) May be asymptomatic in chronic cases
  16. 16. Diagnostic evaluation Urine osmolality >800 mOsm/l: Appropriate renal response <300 mOsm/l: DI 300- 800 mOsm/l: Partial DI or osmotic diuresis
  17. 17. Management Correction of water deficit Rate: 10-12 mEq/l/day (acute symptomatic patients) 5-8 mEq/l/day (chronic asymptomatic patients)
  18. 18. Calculation of free water deficit Free water deficit= {[Na]- 140}/140* TBW Change [Na]= {infusate [Na]- serum [Na]}/ {TBW+1} Intensive Care Med 1997;23:309 Check serum [Na] in every 4 hours
  19. 19. Disorders of potassium balance
  20. 20. Physiology Major intracellular cation serum [K] concentration 3.5- 5.5 mEq/l Average daily intake 1mEq/kg [K] excreted by renal route: mainly in distal collecting duct Excretion is predominantly aldosterone sensitive
  21. 21. Mechanism Spurious hypokalemia Inadequate intake Transcellular shift; insulin alkalosis, catecholamines Excessive [K] loss; renal (diuretics, osmotic diuresis, hyperaldosteronism) extra renal (lower GI tract)
  22. 22. Clinical features Serum [K]> 3.0mEq/l: asymptomatic Fatigue, myalgia and weakness Constipation, paralytic ileus Hypoventilation, rhabdomyolysis
  23. 23. ECG features
  24. 24. Diagnostic evaluation Urine [K]: < 25mEq/day or <15mEq/l in spot sample denotes appropriate renal conservation TTKG: <2- extra renal [K] loss >4- renal [K] loss Acid base status
  25. 25. Management [K] supplementation: Oral vs parenteral Oral dose 40mEq up to every 4 hourly Estimated deficit: 10mEq [K] for every 0.10mEq/l decrement Parenteral: Only in life threatening situations or in patients unable to take orally. Conc: 40mEq/l (peripheral vein) or 100 mEq/l (central vein) Rate: 20mEq/hr ECG and repeated serum [K] monitoring desirable Correct hypomagnesemia if present
  26. 26. Hyperkalemia Serum [K] > 5.0 mEq/l
  27. 27. Mechanism Transcellular shift Hyperosmolarity, beta blockers, tumour lysis, rhabdomyolysis Decreased excretion Renal failure, adrenal insufficiency, type 4 RTA Drugs ACEI, ARB, [K] sparing diuretics, NSAID, Cyclosporine
  28. 28. Presentation Arrhythmia Flaccid paralysis
  29. 29. ECG features
  30. 30. Diagnostic evaluation Rule out pseudohyperkalemia if patient is stable Evaluate renal [K] excretion TTKG > 10: Intact renal [K] excretion TTKG< 7: Impaired renal [K] excretion
  31. 31. Management Hyperkalemia with ECG changes: Medical Emergency
  32. 32. Acute management Calcium gluconate 10ml 10% over 2-3 minutes; onset within minutes, but short live (30- 60 minutes) Dextrose- insulin 10U insulin with 50g dextrose Sodium bi-carbonate Particularly effective when metabolic acidosis is present beta agonists Onset 30 minutes, duration 2-4 hours, lower [K] by 0.5- 1.5 mEq/l
  33. 33. Chronic management Cation exchange resin Intravenous saline with diuretics Oral sodium bi carbonate Avoid [K] rich food Hemodialysis
  34. 34. Disorders of calcium 99% calcium is in the bone, 1% in ECF 50% of serum Ca is free(ionized), 40% is albumin bound and 10% is phosphate salt PTH increases s [Ca] by stimulating bone resorption, increased calcitriol production and renal conservation of [Ca] Calcitriol stimulates intestinal absorption of [Ca]
  35. 35. Hypercalcemia Serum [Ca] > 10.3 mg/dl with normal albumin or ionised [Ca] > 5.2 mg/dl
  36. 36. CAUSES Primary hyperparathyroidism Malignancy Sarcoidosis, tuberculosis
  37. 37. Presentation Asymptomatic Polyuria, nephrolithiasis Anorexia, constipation, vomiting Osteopenia Weakness, fatigue
  38. 38. Management Emergent management required when: serum [Ca]> 12mg/dl or severe symptoms Fluid administration: 0.9% NaCl targeting urine output of 100-150 ml/hr Loop diuretics Prevents reabsorption of [Ca] in loop of Henle
  39. 39. Long term therapy Bisphosphonate Pamidronate 60-90 mg over 2-4 hours: onset within 2days and persists up to 2 weeks Zolindronate 4mg: Once in a month dosing Calcitonin Inhibits bone resorption and increases renal [Ca] excretion Salmon calcitonin 4-8 IU/kg IM or Sc Glucocorticoids Hemodialysis: Only when renal insufficiency is present
  40. 40. Hypocalcemia Serum [Ca] < 8.4 mg/dl with normal albumin or ionised [Ca]< 4.2 mg/dl
  41. 41. Hypoparathyroidism Vitamin D deficiency Drugs Massive blood transfusion Critical illness Etiology
  42. 42. Clinical features Perioral paresthesia and numbness laryngospasm Bradycardia, hypotension, CHF 44
  43. 43. Physical examination Trousseu’s sign: Carpal spasm when blood pressure cuff is inflated over SBP for 3 minutes Chvostek’s sign: Twitching of the facial muscle’s when facial nerve is tapped in front of ear
  44. 44. Management Exclude hyperphosphatemia: If present consider HD along with [Ca] supplementation Exclude hypomagnesemia: Calcium supplementation: IV Calcium: severe symptomatic hypocalcemia 90- 180 mg elemental [Ca] in 100ml D5 over 15- 20minutes Followed by infusion of 0.5-1.5 mg/kg/hour in D5
  45. 45. Magnesium balance 99% intracellular distribution Daily intake 5mg/kg 25% albumin bound Filtered in glomeruli, reabsorbed in loop of Henle and and distal nephron
  46. 46. Hypomagnesemia Plasma [Mg] < 1.7mg/dl Prevalence is 20- 65% among critically ill patients
  47. 47. Mechanism Increased loss osmotic diuresis, diuretic phase of ATN, drugs (loop diuretics, Ampho B, aminoglycosides, etc), GI loss (severe diarrhoea, malabsorption, biliary fistula) Diabetes mellitus, hyperparathyroidism, thyrotoxicosis, acute pancreatitis Decreased intake
  48. 48. Clinical features Symptoms of other metabolic abnormalities. Toraseds de pointes, VT, VF Flattened T- wave, prolonged QRS and U wave in ECG Refractory seizure
  49. 49. Management Actual deficit difficult to correct (6- 24 mg/kg) In severe, 1-2 gm MgSO4 (4- 8 mmol) over 20 minutes, followed by repetition of same dose every 6-8 hours Limit dose of maximum daily dosing 50 mmol
  50. 50. Hypermagnesemia Plasma [Mg]> 2.7 mg/dl: Mild hypermagnesemia Plasma [Mg]> 7 mg/dl: Moderate hypermagnesemia Plasma [Mg]> 10 mg/dl: Severe hypermagnesemai
  51. 51. Presentation Lethargy, weakness, hyporeflexia Loss of DTR Refractory hypotension, arrhythmia Respiratory depression
  52. 52. Management Urgent management required when [Mg]> 8mg/dl In presence of acute symptoms supplementation of calcium is recommended. In patients with normal renal function, usually no treatment is required; volume loading can done In patients with renal failure, HD is the only anaesthesia