1. Disorders of Electrolyte balance
Souvik Maitra
MD, DNB
1

2. Body water distribution

3. Electrolyte distribution

4. Disorders of water balance: Hyponatremia

5. Epidemiology
20% of critically ill patients
15% emergency admission
1-7% surgical patients

6. Classification
Hypotonic
Hypertonic
Isotonic: pseudohyponatremia

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. 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

11. 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

12. 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

13. 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

14. Vasopressin antagonists
Indicated in hypotonic euvolemic hyponatremia

15. Hypernatremia
Serum [Na]> 145mEq/l
Always associated with hypertonicity
Due to water deficit or [Na] gain

16. Mechanism
Water loss
Renal loss: osmotic diuresis, DI (central or nephrogenic)
Extra renal: Diarrhoea (viral, osmotic)
Primary Na gain
Mineralocorticoid excess
Iatrogenic

17. Clinical features
CNS: Altered mental status, confusion, focal neurological
deficit seizure coma
Polyuria, thirst (DI)
May be asymptomatic in chronic cases

18. Diagnostic evaluation
Urine osmolality
>800 mOsm/l: Appropriate renal response
<300 mOsm/l: DI
300- 800 mOsm/l: Partial DI or osmotic diuresis

19. Management
Correction of water deficit
Rate: 10-12 mEq/l/day (acute symptomatic patients)
5-8 mEq/l/day (chronic asymptomatic patients)

20. 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

21. Disorders of potassium balance

22. 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

23. Mechanism
Spurious hypokalemia
Inadequate intake
Transcellular shift;
insulin alkalosis, catecholamines
Excessive [K] loss;
renal (diuretics, osmotic diuresis, hyperaldosteronism)
extra renal (lower GI tract)

24. Clinical features
Serum [K]> 3.0mEq/l: asymptomatic
Fatigue, myalgia and weakness
Constipation, paralytic ileus
Hypoventilation, rhabdomyolysis

25. ECG features

26. 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

27. 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

28. Hyperkalemia
Serum [K] > 5.0 mEq/l

29. 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

30. Presentation
Arrhythmia
Flaccid paralysis

31. ECG features

32. 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

33. Management
Hyperkalemia with ECG changes: Medical Emergency

34. 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

35. Chronic management
Cation exchange resin
Intravenous saline with diuretics
Oral sodium bi carbonate
Avoid [K] rich food
Hemodialysis

36. 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]

37. Hypercalcemia
Serum [Ca] > 10.3 mg/dl with normal albumin or ionised [Ca]
> 5.2 mg/dl

38. CAUSES
Primary hyperparathyroidism
Malignancy
Sarcoidosis, tuberculosis

39. Presentation
Asymptomatic
Polyuria, nephrolithiasis
Anorexia, constipation, vomiting
Osteopenia
Weakness, fatigue

40. 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

41. 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

42. Hypocalcemia
Serum [Ca] < 8.4 mg/dl with normal albumin or ionised [Ca]<
4.2 mg/dl

43. Hypoparathyroidism
Vitamin D deficiency
Drugs
Massive blood transfusion
Critical illness
Etiology

44. Clinical features
Perioral paresthesia and numbness
laryngospasm
Bradycardia, hypotension, CHF
44

45. 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

46. 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

47. Magnesium balance
99% intracellular distribution
Daily intake 5mg/kg
25% albumin bound
Filtered in glomeruli, reabsorbed in loop of Henle and and
distal nephron

48. Hypomagnesemia
Plasma [Mg] < 1.7mg/dl
Prevalence is 20- 65% among critically ill patients

49. 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

50. Clinical features
Symptoms of other metabolic abnormalities.
Toraseds de pointes, VT, VF
Flattened T- wave, prolonged QRS and U wave in ECG
Refractory seizure

51. 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

52. Hypermagnesemia
Plasma [Mg]> 2.7 mg/dl: Mild hypermagnesemia
Plasma [Mg]> 7 mg/dl: Moderate hypermagnesemia
Plasma [Mg]> 10 mg/dl: Severe hypermagnesemai

53. Presentation
Lethargy, weakness, hyporeflexia
Loss of DTR
Refractory hypotension, arrhythmia
Respiratory depression

54. 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