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Stage 4: CSIM 2 > Week 4: Electrolyte disturbances > Flashcards

Week 4: Electrolyte disturbances Flashcards

1
Q

Normal sodium range

A

135-145 mmol/L

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2
Q

Normal potassium range

A

3.5-5.5 mmol/L

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3
Q

Normal calcium range

A

2.2-2.6 mmol/L

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4
Q

How are calcium and phosphate levels affected in chronic renal impairment

A

Low calcium

High phosphate

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5
Q

Causes of low potassium

A

K+ entering cell:

  • metabolic alkalosis
  • insulin
  • adrenergics

K+ can’t come out of cell:
-low magnesium

Loss:

  • V and D, osmotic diuresis, diuretics
  • Cushing’s

Insufficient dietary intake

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6
Q

Causes of high potassium

A

K+ leaving cell:
-cell lysis (eg chemotherapy, burns, haemolysis)

K+ not entering cell:

  • metabolic acidosis
  • low insulin
  • B blockers

Low renin, aldosterone

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7
Q

Why does low magnesium cause hypokalemia

A

Low magnesium inhibits K from crossing cell membrane

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8
Q

Why does Cushing’s cause hypokalemia

A

Excess cortisol acts like aldosterone and binds to Na/K pump

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9
Q

Hyper/hypotension is caused by high/low potassium

A

Hypertension: high potassium

Hypotension: low potassium

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10
Q

Diarrhoea/constipation is caused by high/low potassium

A

Diarrhoea: high potassium

Constipation: low potassium

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11
Q

How do potassium imbalances affect reflexes and muscle strength

A

BOTH:

  • flaccid paralysis
  • decreased reflexes
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12
Q

Drugs that should be avoided in low potassium

A
  • Insulin
  • Adrenergic agonists
  • Steroids
  • Anything that causes more GI loss eg laxatives, diuretics
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13
Q

Drugs that should be avoided in high potassium

A
  • Beta blockers, digoxin
  • ACEi (leads to less aldosterone)
  • Heparin (blocks synthesis of aldosterone)
  • NSAIDs (reduce renin release so less K+ excreted)
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14
Q

What drugs/ compounds cause potassium to LEAVE a cell

A
  1. Metabolic acidosis

2. Rhabdomyolysis

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15
Q

What drugs/ compounds cause potassium to ENTER a cell

A
  1. Insulin
  2. Adrenergics
  3. Metabolic alkalosis
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16
Q

How do thiazide diuretics and lithium affect calcium levels

A

Both cause reduced excretion of calcium from kidney

HYPERCALCAEMIA

17
Q

How are sodium and potassium levels affected in chronic renal impairment

A

Less renin produced

HYPERKALEMIA
HYPONATREMIA

18
Q

How does cortisol affect calcium levels

A

Inhibits calcium absorption

HYPOCALCAEMIA

(so Cushing’s causes hypocalcaemia and Addison’s causes hypercalcaemia)

19
Q

How does phaeochromocytoma affect calcium levels

A

HYPERCALCAEMIA

20
Q

How does hyperthyroidism affect calcium levels

A

HYPERCALCAEMIA

21
Q

How does Addison’s affect sodium levels

A

HYPONATREMIA

Low aldosterone, less reabsorption of Na

22
Q

How does Conn’s affect sodium levels

A

HYPERNATREMIA

More aldosterone, more reabsorption of Na

23
Q

How does Cushing’s affect sodium levels

A

HYPERNATREMIA

More cortisol, similar effect to high aldosterone, more reabsorption of Na

24
Q

How does SIADH affect sodium levels

A

HYPONATREMIA

More ADH, More Na lost in urine

25
Q

How does Diabetes insipidus affect sodium levels

A

HYPERNATREMIA

Less ADH, less NA lost in urine

26
Q

Management of hypernatremia

A

IV dextrose

27
Q

Management of hyponatremia

A

IV sodium
Water restriction

(caution not to overcorrect or this will cause cerebral oedema

28
Q

Management of hyperkalemia (with specific doses)

A
  1. Calcium gluconate (10%, 5-10ml IV)
  2. Insulin (Novorapid 10-20units, IV)
  3. Sabutamol (10-20mg, nebuliser)
  4. GI cation exchangers
  5. Dialysis
29
Q

Management of hypokalemia

A

IV potassium

IV magnesium if this is also low

30
Q

Management of hypercalcaemia

A
  1. IV fluids (do this first!)

2. IV bisphosphonates

31
Q

Management of hypocalcaemia

A

IV calcium

32
Q

Why are pts at risk of electrolyte imbalance after a bladder obstruction

A

Relief of obstruction leads to post obstruction diuresis

Will lose lots of salt and water

33
Q

Signs of hyperkalemia on ECG

state in order at which they appear

A
  1. Tall T wave
  2. Widened flattened T wave
  3. Prolonged PR interval
  4. Widened QRS
  5. Loss of P waves
  6. Sine wave

Also bradycardia at any point

34
Q

Signs of hypokalemia on ECG

state in order at which they appear

A
  1. Flat/ inverted T wave
  2. Prominent U waves
  3. ST depression
  4. Prolonged QU interval (>500ms)
  5. Torsade des pointes
35
Q

Signs of hypercalcaemia on ECG

state in order at which they appear

A
  1. Shortened QT interval

2. J waves (curve on the downward point of the QRS complex)

36
Q

Signs of hypocalcaemia on ECG

state in order at which they appear

A

Prolonged ST segment leading to QTc prolongation

this is the only change

37
Q

Most common cause of primary hyperparathyroidism

A

Solitary parathyroid adenoma

Multiple adenomas, parathyroid hyperplasia, parathyroid carcinoma are also causes, but rarer

Stage 4: CSIM 2 (47 decks)

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