Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

YR5 Chemical Pathology > Potassium and Electrolytes > Flashcards

Potassium and Electrolytes Flashcards

1
Q

What is the serum concentration for normal potassium?

A

3.5-5.3 mmol/L

Most abundant INTRAcellular cation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is potassium regulated by?

A

Angiotensin II + Aldosterone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does aldosterone contribute in terms of electrolyte balance?

A

Aldosterone is stimulated by Angiotensin II and K+

Aldoesterone causes resorption of Na+ and water and excretion of K+ in urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the renin angiotensin aldosterone system

A

Renin from JGA stimulates release of angiotensinogen from liver

Converted to angiotensin I

ACE in Lung converts to angiotensin II

Stimulates adrenals to release Aldosterone

Aldosterone acts on principal cells of cortical collecting tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does high potassium stimulate the adrenals to produce?

A

Aldosterone

To increase potassium loss in urine + maintain potassium in homeostatic range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the main causes of hyperkalaemia?

A

Renal impairment: reduced renal excretion

Drugs: ACEi, ARBS, spironolactone

Low aldosterone: Addison’s disease, Type 4 renal tubular acidosis (low renin, low aldosterone)

Release from cells: rhabdomyolysis, acidosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are ECG changes with hyperkalaemia?

A

Tented T waves

Broad QRS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the treatment for hyperkalaemia?

A

If ECG changes + K+ >6.5:

10ml 10 % calcium gluconate to stabilise cardiac myocardium

100ml 20% dextrose + 10 units insulin bolus

Nebulized salbutamol

Treat underlying cause

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are causes of hypokalaemia?

A

GI loss: vomiting

Renal Loss: MR excess, osmotic diuresis

Redistribution into cells: insulin, beta-agonists, alkalosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the clinical features of hypokalaemia?

A

Nephrogenic DI: resistant to ADH- polyuria + polydipsia.

Muscle weakness

Arrhythmia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do you manage hypokalaemia?

A

Serum K+ 3.0-3.5 mmol/L:

Oral potassium chloride (2 SandoK tablets tds for 48h)

Recheck serum K+

Serum K+ < 3.0 mmol/L:

IV potassium chloride

Max rate 10 mmol per hour

(Rates > 20 mmol per hour are highly irritating to peripheral veins)

Treat the underlying cause e.g. spironolactone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which drug can cause hyperkalaemia?

Furosemide

Bendroflumethiazide

Salbutamol

Ramipril

A

Ramipril

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which drug can cause hypokalaemia?

Spironolactone

Indomethacin

Perindopril

Furosemide

A

Furosemide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the action of aldosterone on the principal cells

A

Binds to mineralocorticoid receptors

Leads to less degradation of Na channels, increasing no. of open channels

Increases Na reabsorption

Lumen becomes more -ve

K+ moves into lumen down electrochemical gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the stimuli for aldosterone secretion?

A

Angiotensin II

High K+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does renal impairment lead to hyperkalaemia?

A

Low GFR e.g. in kidney disease/ drugs = reduced K+ excretion

Low renin e.g NSAIDs, T4 renal tubular acidosis in DM. Less angiotensinogen released + converted, less AII, less aldosterone = reduced K+ excretion

17
Q

How do ACE inhibitors cause hyperkalaemia?

Give 3 examples

A

Less AI converted to AII

Less aldosterone

Less K+ lost

Enalapril, Ramipril, Lisinopril

18
Q

How do angiotensin receptor blockers cause hyperkalaemia?

Give 2 examples

A

Block AII receptors

Less AII action

Less aldosterone

Less K+ lost

Losartan, Candesartan

19
Q

How does Addison’s disease lead to hyperkalaemia?

A

Less Aldosterone

Less K+ lost

20
Q

How do aldosterone antagonists cause hyperkalaemia?

Give an example

A

Less Aldosterone action

Less K+ lost

Spironolactone

21
Q

How does rhabdomyolysis cause hyperkalaemia?

A

K+ leaks from damaged muscle cells in long lie

22
Q

How does acidosis cause hyperkalaemia?

A

H+ moves into cells

K+ lost to maintain electrochemical neutrality

23
Q

What is the alternative dose of dextrose you could give in hyperkalaemia?

A

200ml of 10% dextrose

24
Q

What can cause renal loss of K+ and lead to hypokalaemia?

A

Hyperaldosteronism e.g. Conns + excess cortisol e.g. Cushings

Increased Na delivery to distal nephron

Osmotic diuresis e.g. hyperglycaemia lose K+

25
Q

What can cause re-distribution into the cells and lead to hypokalaemia?

A

Insulin: K+ enters cells

Beta agonsits: stimulate K+ uptake by cells

Alkalosis: H+ moves out of cells, K+ moves into cells

26
Q

Give 2 rare causes of hypokalaemia

A

Renal tubular acidosis type 1 + 2

Hypomagnesaemia.

27
Q

Where are sodium, potassium and chloride re-absorbed in the nephron?

A

Na, K, Cl reabsorbed in ascending limb of LoH

Na, Cl reabsorbed in distal tubule

28
Q

What happens if the transporter in the ascending limb is blocked/ not functioning? Give 2 causes of this

A

More Na delivered to distal nephron, more reabsorbed there, lumen becomes more -ve

K+ lost secondary to lumen being relatively more -ve

Loop diuretics

Bartter syndrome: channels not working, genetic

29
Q

What happens if the Na-Cl transporter in the distal tubule is not functioning/ blocked?

Give 2 causes of this

A

Less Na reabsorbed, more delivered distally, more reabsorbed later in distal nephron

Makes lumen more negative, K+ lost to compensate

Thiazide diuretics: block distal tubule reabsorption of Na

Gitelman syndrome: genetic defect in channels

30
Q

How does increased sodium delivery to the principal cells cause hypokalaemia?

A

More Na reabsorbed here

K+ lost in exchange

31
Q

How does hyperaldosteronism cause hypokalaemia?

A

Conns or Bilateral hyperplasia

Increased aldosterone

Increases Na reabsorption

More K+ lost

32
Q

What other endocrine pathology can cause renal losses of potassium and thus hypokalaemia?

A

Cushings

Excess cortisol can bind to mineralocorticoid receptors

33
Q

What are the clinical features of hypokalaemia?

A

Muscle weakness

Cardiac arrhythmia

Polyuria + polydipsia (Nephrogenic DI- as interferes with action of ADH)

34
Q

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

A

Aldosterone: Renin ratio

In primary hyperaldosteronism: aldosterone should be high, renin should be suppressed

YR5 Chemical Pathology (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions