U&E's (Na & K)

Question 1

What is the ratio of IFC to EFC?

Answer 1

2:1

Question 2

What ion largely determines EFC osmotic pressure?

Answer 2

Sodium

Question 3

What ion largely determines IFC osmotic pressure?

Answer 3

Potassium

Question 4

What is the ratio between plasma & interstitial fluid in EFC?

Answer 4

1:3

Question 5

How is osmotic pressure maintained?

Answer 5

The sodium-potassium pump

Question 6

Where is 95% of sodium re-absorbed?

Answer 6

The renal tubules

Question 7

What function does sodium have within the cells?

Answer 7

• Required for nerve cell conduction

- Maintains acid-base balance

Question 8

How is the homeostasis of sodium & water maintained?

Answer 8

ADH & aldosterone

Question 9

What drugs may cause hypovolemic hyponatraemia?

Answer 9

• Loop diuretics e.g. furosemide
• Thiazide diuretics e.g. bendrofluthiazide
• aldosterone antagonists e.g. Spironolactone

Question 10

What are the three types of hyponatraemia?

Answer 10

• hypovolemic hyponatraemia
• hypervolemic hyponatraemia
• euvolemic hyponatremia

Question 11

What causes hypovolemic hyponatraemia?

Answer 11

sodium (and water) loss (BUT - more sodium than water is lost

Question 12

What causes hypervolemic hyponatraemia?

Answer 12

combined water and sodium excess (BUT - greater increase in water)

Question 13

What causes euvolemic hyponatremia?

Answer 13

Water excess - actual body sodium is near normal?

Question 14

What drugs may cause SIADH?

Answer 14

• SSRI’s
• MAOI’S
• Phenothiazines
• TCA’s
• PPI’s
• NSAID’s
• Haloperidol

Question 15

What is sick cell syndrome? and why?

Answer 15

• non-specific mild hyponatraemia seen in generalised illness.
• Caused by decreased cellular energy leading to increased cell wall permeability causing water to shift into the EFC.

Question 16

Treatment of hyponatraemia due to sodium loss?

Answer 16

• Appropriate replacement e.g. 0.9 % NaCl or Oral sodium supplement + increased oral fluid intake.

Question 17

Treatment of hyponatraemia due to water excess?

Answer 17

• Fluid restriction

- Consider demeclocycline

Question 18

What’s the dosage of demeclocycline used to treat dilutional hyponatraemia?

Answer 18

• 0.9 - 1.2 g daily in divided doses

- Maintenance 600 - 900 mg

Question 19

What are the two main causes of hypernatraemia?

Answer 19

• Dehydration

- Excess sodium

Question 20

What drugs may cause hypernatraemia?

Answer 20

• Corticosteroids
• NSAID’s
• Effervescent tablets

Question 21

Treatment of hypernatraemia?

Answer 21

• Identify cause.

- Restrict drug sources of sodium

Question 22

What causes hypokalaemia?

Answer 22

• Reduced intake
• Increased renal excretion
• Cushing’s syndrome
• Loop & thiazide diuretics

Question 23

What causes hyperkalaemia?

Answer 23

• Excess intake
• Reduced renal excretion
• ACE inhibitors, aldosterone receptor antagonists, NSAID’s, potassium sparing diuretics, heparins

Question 24

Treatment of hyperkalaemia?

Answer 24

• Identify cause and stop or switch to alternative (if caused by drugs)
• Calcium resonium
• Calcium gluconate

Question 25

Where are magnesium ions predominantly found?

Answer 25

IFC

Question 26

What drugs may cause hypomagneseaemia?

Answer 26

- Amphotericin - Aminoglycosides - Cisplatin - Ciclosporin

Question 27

What are the symptoms of hypomagneseaemia?

Answer 27

- Respiratory muscle paralysis - Heart block - Altered mental state

Question 28

What may treatment of hypomagneseaemia affect?

Answer 28

May affect correction of hypokalaemia