Hypo/hyperkalaemia

Question 1

What is the definition of hyperkalaemia?

Answer 1

serum potassium concentration >5.5 mmol/L

Question 2

What are 3 groups of causes of hyperkalaemia?

Answer 2

1. Imapired excretion from the kidney
2. Increased release from cells
3. Pseudohyperkalaemia/ artefact

Question 3

What are 10 causes of hyperkalaemia due to impaired excretion?

Answer 3

1. AKI
2. CKD
3. ACE inhibitors
4. Potassium sparing diuretics e.g. spironoclactone
5. NSAIDs
6. Heparin/ LMWH
7. Ciclosporin
8. High dose trimethoprim
9. Hypoaldosteronism (e.g. renal tubular acidosis type 4)
10. Addison’s disease

Question 4

What are 7 causes of hyperkalaemia due to increased release from cells?

Answer 4

1. Lactic acidosis
2. Insulin deficiency
3. Rhabdomyolysis
4. Tumour lysis syndrome
5. Massive haemolysis
6. Digoxin toxicity (NB: this can be precipitated by hypokalaemia)
7. Beta blockers

Question 5

What are 4 causes of pseudohyperkalaemia/artefact causes of hyperkalaemia?

Answer 5

1. Haemolysis (traumatic venepuncture, prolonged tourniquet use, fist clenching)
2. Delayed analysis (K+ leaks out of red blood cells)
3. Contamination with potassium EDTA anticoagulant in FBC bottles
4. Thrombocytopenia (K+ leaks out of platelets during clotting)

Question 6

What are 7 ECG changes in hyperkalaemia?

Answer 6

1. Tall, tented T waves
2. Broad QRS complexes
3. Prolonged PR interval
4. Flattened p waves
5. Idioventricular rhythms
6. sine wave paterns
7. VF/ asystole

Question 7

What are 4 aspects of management of hyperkaelamia?

Answer 7

1. Give 10ml 10% calcium gluconate over 10 minutes - cardioprotective
2. IV insulin: 10 units of Actrapid in 50ml of 50% dextrose
3. Nebulised salbutamol
4. Calcium resonium 15g orally (or rectally)

Question 8

When should you treat for hyperkalaemia?

Answer 8

potassium >6.5 or any ECG changes

Question 9

What is the mechanism of action of calcium gluconate when treating hyperkalaemia?

Answer 9

cardioprotective (does’t reverse hyperkalaemia)

Question 10

What is the mechanism of IV insulin + dextrose infusion when treating hyperkalaemia?

Answer 10

causing intracellular shift of potassium - only transient (also need to treat underlying cause)

Question 11

What is the mechanism of action of nebulised salbutamol to treat hyperkalaemia?

Answer 11

intracellular shift of potassium - transient

Question 12

In addition to the 4 initial steps of management of hyperkalaemia, what are 3 further aspects of management?

Answer 12

1. check contributing drugs e.g. ACEi, spironolactone
2. Once initial measures completed, recheck U+Es and ECG and glucose
3. Check urinary potassium

Question 13

Why can heparin/ LMWH cause hyperkalaemia?

Answer 13

inhibits aldosterone release

Question 14

What are 5 types of drugs which can cause hyperkalaemia?

Answer 14

1. Potassium sparing diuretics e.g. spironolactone
2. Angiotensin-converting enzyme inhibitors
3. Angiotensin-II receptor blockers e.g. losartan
4. Ciclosporin
5. Heparin

Question 15

Why is metabolic acidosis associated with hyperkalaemia?

Answer 15

hydrogen and potassium ions compete with each other for exchange with sodium ions across cell membranes and in the distal tubule

Question 16

What are 7 foods that are high in potassium?

Answer 16

1. Salt substitutes - i.e. contain potassium rather than sodium
2. Bananas
3. Oranges
4. Kiwi fruit
5. Avocado
6. Spinach
7. Tomatoes

Question 17

What is a type of drug which can potentially cause hyperkalaemia in patients with renal failure and why?

Answer 17

beta blockers - interfere with potassium transport into cells (hence why salbutamol, a beta agonist, can be used as emergency treatment)

Question 18

What is more effect, oral or rectal (enema) calcium resonium?

Answer 18

rectal - because potassium is secreted by the rectum

Question 19

How does calcium resonium work to treat hyperkalaemia?

Answer 19

it’s a resin that binds potassium in the gut to increase excretion in the rectum

Question 20

What is the management for persistent hyperkalaemia in patients with AKI when all other methods have failed?

Answer 20

dialysis: haemofiltration/haemodialysis

Question 21

What is the definition of hypokalaemia?

Answer 21

serum potassium <3.5 mmol/L

Question 22

What are 2 ways that causes of hypokalaemia can be split?

Answer 22

1. renal and extra-renal
2. with or without hypertension

Question 23

What is the difference between renal and extra-renal causes of hypokalaemia in terms of investigations?

Answer 23

urinary potassium; >20 mEq/L in renal causes, <20 mEq/L in extra-renal

Question 24

What are 5 renal causes of hypokalaemia?

Answer 24

1. Diuretis (e.g. furosemide, thiazides)
2. Renal tubular acidosis
3. Bartter’s, Liddle’s and Gitelman’s syndromes
4. Endocrine causes (hyperaldosteronism, Cushing’s)
5. Hypomagnesaemia

Question 25

What are 3 extra-renal causes of hypokalaemia?

Answer 25

1. Inadequate oral intake 2. Gut losses (e.g. diarrhoea, vomiting, ileostomy, VIPoma, Zollinger-Ellison syndrome) 3. Redistribution into cells (e.g. beta agonists, insulin, theophylline, alkalosis)

Question 26

What are 4 causes of hypokalaemia with hypertension?

Answer 26

1. Cushing's sndrome 2. Conn's syndrome (primary hyperaldosteronism) 3. Liddle's syndrome 4. 11-beta hydroxylase deficiency (accounts for 90% of congenital adrenal hyperplasia cases but this is NOT assoc/w HTN)

Question 27

What is a drug which can potentially cause hypokalaemia associated with hypertension?

Answer 27

Carbenoxolone (anti-ulcer drug) also liquorice excess

Question 28

What are 5 causes of hypokalaemia without hypertension?

Answer 28

1. Diuretics 2. GI loss (e.g. diarrhoea, vomiting) 3. Renal tubular acidosis (type 1 and 2) 4. Bartter's syndrome 5. Gitelman syndrome

Question 29

What are 2 clinical features of hypokalaemia?

Answer 29

1. Muscle weakness 2. Hypotonia

Question 30

Which drug must you be careful with in hypokalaemia?

Answer 30

digoxin toxicity - hypokalaemia prediposes to digoin toxicity also take care if on diuretics

Question 31

What are 5 ECG features of hypokalaemia?

Answer 31

1. U waves 2. small or absent T waves 3. prolonged PR interval 4. ST depression 5. long QT (U have no P and no T but long PR and long QT)

Question 32

What are 4 causes of hypokalaemia with alkalosis?

Answer 32

1. Vomiting 2. Thiazide and loop diuretics 3. Cushing's syndrome 4. Conn's syndrome (primary hyperaldosteronism)

Question 33

What are 4 causes of hypokalaemia with acidosis?

Answer 33

1. Diarhoea 2. Renal tubular acidosis 3. Acetazolamide 4. Partially treated DKA

Question 34

What should be the approach when treating hypokalaemia caused by magnesium deficiency?

Answer 34

may need to correct magnesium deficiency before potassium level can be normalised

Question 35

What are 6 investigations to perform in hypokalaemia?

Answer 35

1. ECG 2. U+Es 3. chloride 4. bicarbonate 5. glucose 6. Urinary potassium and chloride

Question 36

What is the treatment of mild hypokalaemia?

Answer 36

oral slow release potassium chloride (Sando K) treat causes, check potassium regularly

Question 37

What is the management of severe hypokalaemia? 5 aspects

Answer 37

1. Continuous cardiac monitoring 2. Check and correct magnesium (low Mg causes renal K+ wasting) 3. IV infusion of 1L 0.9% saline containing 40 mmol KCl 4. _Avoid_ glucose and bicarbonate solutions 5. Treat cause(s)

Question 38

What is the maximum rate of potassium replacement in hypokalaemia?

Answer 38

10 mmol/L hour

Question 39

What will need to be done to treat hypokalaemia if a faster rate of potassium replacement is required than 10 mmol per hour?

Answer 39

central line will need to be inserted - ITU/ call seniors etc.