Potassium

Question 1

K+ is reabsorbed in the PCT and secreted in the collecting duct for renal excretion. What governs this?

Answer 1

Mineralocorticoid/aldosterone
=> increased aldosterone causes hypokalemia in serum and increased K+ in urine

Question 2

Match Hyperkalaemia and Hypokalaemia to Metabolic acidosis Metabolic alkalosis Respiratory acidosis Respiratory alkalosis. Each can be used once, multiple times or not at all

Answer 2

Hyperkalaemia is associated with metabolic acidosis
Hypokalaemia is associated with metabolic alkalosis

This is because K+ and H+ can be thought of as competitors. Hyperkalaemia tends to be associated with acidosis as most K+ is intracellular => in acidosis H+ needs to enter cells to maintain haemostasis (pH normal) +> K+ is shifted into the blood or extracellular space

Question 3

Does DKA cause hypo or hyperkalaemia? why?

Answer 3

DKA causes hyperkalaemia typically (think acid = hyper)
BUT during the treatment of DKA it will become hypokalaemic as insulin is given in its treatment just like with the tx of hyperkalaemia => K+ moves intracellularly => may cause hypokalaemia

Question 4

Why does DKA and HHS (hyperosmolar hyperglycaemic state) cause hyperkalaemia

Answer 4

Due to reduced insulin

Question 5

Does addison’s disease cause hyper or hypokalaemia? Why?

Answer 5

Hyperkalaemia Due to aldosterone/mineralocorticoid deficiency

Question 6

Does Cushing’s cause Hyper or hypo kalaemia? why?

Answer 6

Hypokalaemia due to aldosterone/mineralocorticoid excess

Question 7

Give an example of an aldosterone antagonist
Does it cause hypokalaemia or hyperkalaemia?

Answer 7

Spironolactone
Hyperkalaemia as it is antagonising aldosterone therefore causes aldosterone deficiency => reduced excretion => hyperkalaemia

Question 8

Do ACE inhibitors cause hypo or hyperkalaemia?
Why?
What are some other drugs that may cause that due to the same reason?

Answer 8

Hyper
Reduced K+ excretion
ARBs/Aldosterone antagonists/NSAIDs

Question 9

Does Digoxin cause Hypo or hyperkalaemia?
Why?
Is there any other drug that may cause that due to the same reason?

Answer 9

Bisoprolol specifically not all beta blockers (i think)

Question 10

Give 10 causes of Hyperkalaemia

Answer 10

Diseases:
AKI, CKD
DKA, HHS (hyperosmolar hyperglycaemia) - due to reduced insulin
Addison’s disease - aldosterone/mineralocorticoid deficiency

Medications:
ACEi/ARBs/Aldosterone antagonists/NSAIDs -> reduced K+ excretion
Digoxin/Bisoprolol -> reduced K+ cellular transport

Cellular release: Haemolysis, rhabdomyolysis

Question 11

What ECG findings are consistent with hyperkalaemia?

Answer 11

Tented T waves
QRS widening
Arrhythmias

Question 12

How would you manage hyperkalaemia

Answer 12

Do you ABCDE and call for help stuff
1) Assess: ECG (tented T waves, QRS widening, arrhythmias)
2) Stabilise heart: IV Calcium gluconate 10ml 10% over 10 minutes THEN reassess ECG and repeat if not resolved in 10 minutes
3) Shift K+ intracellularly: Insulin (act-rapid cuz short acting) + 50ml 50% glucose (dextrose)
4) Excrete excess K+: Loop or thiazide diuretic
5) If refractory -> Haemodialysis

Question 13

Give 10 causes of Hypokalaemia

Answer 13

Vomiting/severe diarrhoea => laxatives, anorexia, bulimia nervosa
Alcoholism
Partially treated DKA => insulin in tx

Medications:
Loop and Thiazide diuretics
Corticosteroids (think Cushings)

Question 14

How would you manage hypokalaemia

Answer 14

First I would check magnesium levels. If low I will supplement with oral -> IV magnesium +/- correct underlying cause

Then simply give oral -> IV K+

Question 15

What is the effect of hypomagnesia on K+ levels?

Answer 15

hypomagnesia may occur with hypokalaemia, exacerbate it, or render it refractory to tx with K+ supplementation