Potassium Balance

Question 1

Normal Serum concentration of potassium?

Answer 1

3.5 - 5 mmol/L

Question 2

Which hormones are involved in renal regulation of potassium?

Answer 2

Angiotensin II

Aldosterone

Question 3

what stimulates the production of renin?

Answer 3

Reduced perfusion (BP) or

low sodium

Question 4

where is renin made?

Answer 4

juxtaglomerular cells of the Kidney

Question 5

what cleaves angiotensinogen to angiotensin I

Answer 5

RENIN

Question 6

where is angiotensinogen made?

Answer 6

LIVER

Question 7

which enzyme catalyses conversion of angiotensin 1 to 2

Answer 7

ACE

angiotensin converting enzyme

Question 8

where is ACEnzyme found?

Answer 8

Lungs

Question 9

what is the role of Angiotensin II?

Answer 9

• Angiotensin II stimulates the adrenal glands to produce aldosterone

Question 10

what is the role of aldosterone?

Answer 10

• Aldosterone will stimulate:

sodium reabsorption (into blood)

potassium excretion (into urine)

in the KIDNEY

Question 11

What electrolyte balance does aldosterone release more greatly effect and why?

Answer 11

Potassium: Hyperkalaemia is also a potent stimulus for aldosterone release.

aldosterone leads to Potassium loss

water will also be drawn in with the sodium so this response should NOT greatly affect sodium concentration

Question 12

on which cells does Aldosterone stimulate:

sodium reabsorption (into blood)

potassium excretion (into urine)

Answer 12

Principal cells

cortical collecting tubule

Question 13

Sodium reabsorption from the lumen leads to what electrical potential?

what is the effect of this?

Answer 13

negative potential so;

potassium moves down into the lumen to rectify this

Question 14

Na reabsorption through which channels?

Answer 14

ENaC (epithelial sodium channels)

Question 15

sodium leaves the lumen through the ENAC channels and enters the blood through which channels?

Answer 15

NA/K ATPase

Question 16

how many sodium and potassium ions transported by NA/K ATPase?

Answer 16

3 NA out into blood

2K into cell

Question 17

Potassium enters the lumen/urine through which receptor?

Answer 17

ROMK

Renal outer medullary potassium channel (ROMK

Question 18

How does aldosterone stimulate sodium reabsorption in the kidney?

Answer 18

simple version;

Aldosterone binds to mineralocorticoid receptors

in the principal cells

and stimulates the transcription of ENaC channels

via which NA moves out of the lumen

Question 19

What is the role of which aldosterone and sgk1 in Na reabsorption?

Answer 19

Aldosterone binding to MR

increases SGK1 which inhibits Nedd4

= less Na channel degradation

Question 20

What are the stimuli for aldosterone secretion?

Answer 20

Angiotensin II

Potassium

Question 21

case:

Lady presents with fatigue, muscle weakness, weight loss, and depression.

on examination she has a tan and hyperpigmentationon areas i.e. mucosa and low blood pressure.

what is the Cause of Hyperkalaemia?

treatment for conditions?

Answer 21

Addison’s disease - adrenal failure

treatment;
hydrocortisone or prednisolone

* 10 mL 10% calcium gluconate
* 100 mL 20% dextrose + 10 units of insulin

Question 22

case:

man presents with worsening stomach pain and maleania. he has chronic back pain and is on regular diclofenac for many years.

bloods show high K

what is the Cause of Hyperkalaemia?
treatment?

Answer 22

NSAIDs -> reduced renin activity = low aldosterone

discontinue nsaid

10 mL 10% calcium gluconate
• 100 mL 20% dextrose + 10 units of insulin

Question 23

60 year old man with high BP has been taking spironolactone and Enalopril and Losartan for years.

he presents with Palpitations, muscle pain, muscle weakness, numbness.

what is the problem?

treatment?

Answer 23

Aldosterone antagonists and ACE inhibitor Angiotensin II receptor blockers induced hyperkalaemia.

change diuretics

10 mL 10% calcium gluconate
• 100 mL 20% dextrose + 10 units of insulin

Question 24

when do we treat hyperkalaemia?

Answer 24

This is when potassium is >6.5 or there are ECG CHANGES.

Question 25

name complications of High K?

Answer 25

arrhythmia – death

Question 26

man with copd uses salbutamol.

he also suffered anaphylactic reaction and used epinephrine/adrenaline.

he then experienced:

* Muscle weakness 
* Cardiac arrhythmia 
* Polyuria and polydipsia

what’s wrong?

Answer 26

2 Beta agonists induced hyPOkalaemia

Question 27

a man experiences Muscle weakness
• Cardiac arrhythmia
• Polyuria and polydipsia

he has a long term condition;
Weight gain and fatty tissue deposits,
Pink or purple stretch marks (striae)
Thinning, fragile skin that bruises easily.

what’s wrong?

Answer 27

Cushings induced hyPOkalaemia

cushings = high cortisol which binds to MR receptor = high aldosterone

Question 28

man is taking bendroflumethiazide and furosemide.

he is at risk of what electrolyte imbalance?

Answer 28

hypokalaemia

loop and thiazide diuretic

Question 29

Loop diuretics work on which part of the nephron?

Answer 29

ASCENDING LOOP OF HENLE

Question 30

THIAZIDE diuretics work on which part of the nephron?

Answer 30

DISTAL CT

Question 31

woman with type 1 diabetes takes insulin.

she is at risk of what electrolyte imbalance?

Answer 31

hypokalaemia

insulin mediated

Question 32

Which screening test would you order in a patient with hypokalaemia and hypertension?

Answer 32

○ Aldosterone: renin ratio

In primary hyperaldosteronism, you would expect a high aldosterone: renin ratio because the high aldosterone will suppress renin

Question 33

Management of Hypokalaemia

Answer 33

Potassium chloride

• Serum K+: 3.0-3.5 mmol/L
	○ Oral potassium chloride 
	○ Re-check serum K+ concentration

• Serum K+: < 3.0 mmol/L
	○ IV potassium chloride 
	○ Maximum rate: 10 mmol/hr 
	○ Rates > 20 mmol/hr are highly irritating to peripheral veins 

• Treat the underlying cause