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Electrolyte Imbalances and Biochemistry Flashcards

1
Q

Causes of hypernatraemia?

A
  1. Fluid Loss
    • Diarrhoea, burns, fever, glycosuria (DM, DI)
  2. Inadequate Intake
    • Impaired thirst response in elderly or hypothalamic disease
  3. Excess Na+
    • ​​Iatrogenic (excess crystalloids or Na+ containing drugs – IV Ben Pen), Conn’s syndrome
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2
Q

Presentation of hypernatraemia?

A

Anorexia, thirst, nausea, weakness, hyperreflexia, confusion, ↓GCS

Assess volume status

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3
Q

Investigations in hypernatraemia?

A

Daily serum Na+ concentrations

Renal function and electrolytes

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4
Q

Management of hypernatraemia?

A

Mild/Euvolaemic

  • Encourage patient to drink water
  • Slow infusion 5% dextrose

Severe/Hypovolaemic

  • Slow infusion of 0.9% NaCl
  • Glucose 5% thereafter to correct water deficit

Severe/Hypervolaemic

  • Slow infusion of 5% glucose
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5
Q

Caution in treatment of hypernatraemia?

A
  • If extracellular Na+ rapidly corrected, osmotic forces will drive fluid into cells, causing lysis resulting in neurological damage and death –> CENTRAL PONTINE DEMYELINATION

Aim for slow correction of Na+ - 10mmol/L/24h at very most. Treatment guided by volume status.

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6
Q

Causes of hyponatraemia?

A

Usually Dilutional

  • Diuretics, Addison’s disease, DKA, D+V, burns
  • SIADH
    • Malignancy (lung, pancreas, lymphoma)
    • Lung infections
    • CNS infections or vascular events
    • Drugs (SSRIs, tricyclics, carbamazepine, antipsychotics)
    • Idiopathic

Pseudohyponatraemia = taking blood from arm with IV fluids running, a lipaemic sample or osmotically active substances in blood (e.g. hyperglycaemia).

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7
Q

Causes of hyponatraeima if HYPOvolaemic?

A
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8
Q

Causes of hyponatraeima if EUvolaemic?

A

(ADH leads to more concentrated urine)

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9
Q

Causes of hyponatraemia if oedematous?

A

Like SIADH but because of oedema

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10
Q

Presentation of hyponatraemia?

A

Headache, confusion, drowsiness, seizures, coma, death

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11
Q

Investigations in hyponatraemia?

A

Daily serum sodium concentrations, electrolytes and renal function

Blood/Urine Osmolalities

  • In SIADH…
    • Urine = high Na+ and high osmolality (concentrated)
    • Blood = low Na+ and low osmolality (concentrated)

Daily weights (1 litre = 1kg)

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12
Q

Management of hyponatraemia?

A

Depends on volume status and underlying cause. If mild and asymptomatic, no treatment usually required.

Treat cause!

Overloaded

  • Fluid restrict

Hypovolaemic

  • Slow 0.9% NaCl – to replace lost fluid

Euvolaemic (SIADH)

  • Correct cause + slow 0.9% NaCl
  • Fluid restrict to 1 L/day. If resistant to fluid restriction, inhibition of ADH may be required –> demeclocycline.

Seizures/Coma

  • Hypertonic saline - SENIOR SUPPORT
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13
Q

Causes of hyperkalaemia?

A
  1. Reduced Renal Excretion
    • AKI/CKD, drugs (potassium-sparing diuretics, ACEi, NSAIDs), Addison’s
  2. Excess K+ Load
    • Iatrogenic, massive blood transfusion
  3. Increased Cellular Release
    • Acidosis, tissue breakdown (rhabdomyolysis, haemolysis)
  4. Pseudo-Hyperkalaemia
    • Haemolysis, EDTA-contaminated sample
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14
Q

Investigations in hyperkalaemia?

A
  • ECG – low flat P-wave, wide bizarre QRS complex becoming sinusoidal, tall tented T-waves, VF.
  • Bloods – urgent repeat U+E; if K+ <7mmol/L with no new ECG changes or sample is haemolysed, repeat sample, otherwise follow treatment plan. Digoxin levels – toxicity will worsen hyperkalaemia.
  • ABG – for acidosis if acute renal failure
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15
Q

What is this?

A

Sine wave - pre-terminal rhythm of hyperkalaemia

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16
Q

When does hyperkalaemia require management?

A

Serum K+ of >6.5 or hyperkalaemia with ECG changes requires immediate treatment

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17
Q

Management of Hyperkalaemia?

A
  1. Calcium Gluconate 10% - 10ml IV over 5 mins
    • Repeat every 10 min up to 50ml until K+/ECG corrected
  2. Insulin/Dextrose - 10 units actrapid in 100ml 20% glucose
    • Check CBG before, during and after
    • Check K+ decreasing at 30 mins and overall result at 2 hours
  3. Salbutamol - 5mg neb
  4. Calcium Resonium 15g TDS/QDS PO
    • Takes 24h to work
    • Constipates (give with lactulose)
  5. Furosemide
    • With IV fluids if necessary – enhances K+ excretion
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18
Q

Treatment of refractory hyperkalaemia?

A

Haemodialysis

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19
Q

Causes of hypokalaemia?

A
  1. ↑Renal Excretion
    • Diuretics (except K+ sparing)
    • Endocrine (steroids, Cushing’s, Conn’s)
    • Renal tubular acidosis
    • Hypomagnasaemia
  2. Other K+ loss
    • D+V
  3. ↑Cellular Uptake
    • Salbutamol, insulin, alkalosis
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20
Q

What is renal tubular acidosis?

A

Failure of kidneys to acidify urine (normal anion gap)

Either…

  • Not enough bicarb absorption (proximal)
  • Not enough H+ excretion (distal)
21
Q

Presentation and complication of hypokalaemia?

A

Symptoms

  • Weakness, cramps, tetany, palpitations, nausea, paraesthesia

Signs

  • Muscle weakness, hypotonia, arrhythmias, hyporeflexia

Complications

  • Hypokalaemia increases risk of digoxin toxicity
22
Q

Investigations in hypokalaemia?

A
  • ECG – prolonged PR interval, depressed ST segment, small/inverted T waves, prominent U-wave
  • Bloods – U+E (check for other imbalances, especially ↓Mg2+
  • ABG – if alkalosis suspected

No pot and no T - long PR and a long QT

23
Q

What is this?

24
Q

Management of hypokalaemia?

A

>2.5, No ECG Changes

  • Sando-K – 2 tablets TDS for 3/7 OR
  • Add 20-40 mmol/L KCl to IV fluids
  • Monitor U+E –> replace any concurrent ↓Mg2+ (8mmol MgSO4 in 100ml 0.9% saline IV over 1h)

<2.5 or ECG Changes

  • 40mmol/L KCl in 1L 0.9% saline IV over 6 hours (unless oliguric)

Do not replace K+ faster than 10mmol/h outside of HDU/ICU

25
Q

Definition of hypo/hypercalcaemia?

A

Hyper = >2.60 (treat at 3.0)

Hypo = <2.20

26
Q

Causes of hypercalcaemia?

A
  1. ↓Renal Excretion
    • Drugs (thiazide diuretics)
  2. ↑Release from Bone
    • Bony mets (↑ALP) – PB KTL
    • Myeloma (ALP normal)
    • Sarcoidosis
    • Thyrotoxicosis
  3. Excess PTH
    • Primary hyperparathyroidism (↑PTH) or tertiary hyperparathyroidism (↑↑↑PTH)
  4. Excess Vitamin D
    • Excess vitamin D intake
  5. Dehydration
    • Urea and albumin raised
27
Q

Causes of hypercalcaemia? (mnemonic)

A

RHINOS

  • *R**enal insufficiency (2o/3o hyperparathyroidism)
  • *H**yperparathyroidism
  • *I**atrogenic (overuse of vitamin D, Ca2+, thiazides)
  • *N**eoplasms
  • *O**ther endocrinopathies (hyperT, Addison’s)
  • *S**arcoidosis
28
Q

Presentation of hypercalcaemia?

A

If mild - asymptomatic

Severe - bone pain, renal colic, N+V, polyuria, altered consciousness, shortened QT interval

BONES, STONES, GROANS, PSYCHIATRIC OVERTONES

29
Q

Investigations in hypercalcaemia?

A

Investigate for cause if not clear

  • U+Es, ALP, PTH, phosphate
  • Myeloma screen/Bence-Jones protein
  • Serum ACE (if sarcoid suspected)
  • Isotope bone scan (if bony mets suspected)

ECG - shortened QT. Continuous cardiac monitoring if severe hypercalcaemia

30
Q

Management of hypercalcaemia?

A

Remove any underlying cause

Restrict dietary calcium

Rehydration

  • NaCl 0.9% –> 1L 4-6 hourly for 24 hours; then 6 hourly for 48-72 hours with adequate K+
  • Add loop diuretics once hydrated to enhance calcium excretion and prevent fluid overload (furosemide 80-100 mg OD)

Bisphosphonates

  • Pamidronate infusion (can be started during rehydration)
  • Dilute with NaCl 0.9%/glucose 5%
  • Takes 2-4 days to have effect – max effect after 1 week
31
Q

Causes of hypocalcaemia?

A
  1. ↑Renal Excretion
    • Loop diuretics, CKD (↑PO43-), hypomagnasaemia
  2. ↑Deposition in Bone
    • Bisphosphonates
  3. ↓/Ineffective PTH
    • Hypoparathyroidism (surgical/congenital)
    • Pseudohypoparathyroidism (resistance to PTH)
  4. ↓Vitamin D
    • Deficiency (osteomalacia, rickets)
32
Q

Presentation of hypocalcaemia?

A

Symptoms

  • Tetany, paraesthesia, cramps, anxiety, seizures

Signs

  • Chovstek’s sign
  • Trousseau’s sign
33
Q

Investigations in hypocalcaemia?

A

Bloods

  • U+E
  • PTH
  • Phosphate, magnesium

ECG –> long QT (continuous cardiac monitoring if severe)

34
Q

Management of mild hypocalcaemia?

A

Treat cause –> vitamin D deficiency

  • Load with 100,000 units colecalciferol STAT and give adcal-D3 maintenance
  • Monitor patients on digoxin – IV calcium can increase digoxin toxicity

Mild

  • Oral calcium
    • Calcichew tablets – up to 40 mmol per day (12.6 mmol per tablet)
35
Q

Management of severe hypocalcaemia?

A

Calcium gluconate 10% 10 ml IV slowly over 10-30 mins

  • Dilute in 40ml NaCl or 5% dextrose
  • Repeat until asymptomatic
  • Follow with infusion if required
    • 40ml 10% calcium gluconate in 1L dextrose/NaCl over 4-8 hours
    • ECG monitoring required
36
Q

Biochemical profile of dehydration?

A
  • Raised urea disproportionate to a smaller increase in creatinine
  • Raised haematocrit (PCV)
  • Low urine volume
  • Decreased skin turgor

Dehydration affects urea more than creatinine because in dehydration a greater amount of urea is reabsorbed by the kidney - creatinine is hardly reabsorbed at all.

37
Q

Biochemical profile of abnormal kidney function? (2 types)

38
Q

Comparison of low GFR and tubular dysfunction?

39
Q

Biochemical profile of thiazide and loop diuretics?

A

↓Na+

↓K+

↑HCO3-

↑urea

40
Q

Comparison of serum biomarkers in bone disease?

41
Q

Biochemical profile of hepatocellular disease?

A
  • ↑Bilirubin
  • ↑↑AST
  • ↑ALT
  • ↓Albumin (slightly)
  • ↑Clotting times
42
Q

Biochemical profile of cholestasis?

A

↑Bilirubin

↑↑yGT

↑↑ALP

↑AST

43
Q

Biochemical profile of excess alcohol?

A

Evidence of hepatocellular disease

↑yGT

↑MCV

44
Q

Biochemical profile of Addison’s?

A

↑K+

↓Na+

↑urea

45
Q

Biochemical profile of Cushing’s?

A

↓K+

↑HCO3-

↑Na+

46
Q

Biochemical profile of Conn’s syndrome?

A

↓K+

↑HCO3-

Na+ normal or ↑

HTN

47
Q

Biochemical profile of diabetes insipidus?

A

↑Na+

↑Plasma osmolality

↓urine osmolality

(Hypercalcaemia and hypokalaemia may cause nephrogenic diabetes insipidus)

48
Q

Biochemical profile of SIADH?

A

↓Na+

↓ or normal urea and creatinine

↓plasma osmolality

↑urine osmolality

↑urine Na+ (20 mmol/L)

- FINALS (24 decks)

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