Chempath 13: Potassium And Electrolytes Flashcards

1
Q

Which cells release renin ?

A

Junta-glomerular cells in the kidneys

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2
Q

What is the role of renin ?

A

Cleaves angiotensinogen to angiotensin 1

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3
Q

Which enzyme cleaves angiotensin 1 to angiotensin 2 ?

A

ACE

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4
Q

Where is ACE produced ?

A

The lungs

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5
Q

What is the role of angiotensin 2 ?

A

Stimulate adrenal cortex to produce aldosterone
Causes vasoconstriction
Stimulates the CNS to release ADH (vasopressin)

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6
Q

What causes renin release ?

A

Low sodium conc.

low perfusion pressure

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7
Q

Which section of the adrenal cortex produces aldosterone ?

A

Zona glomerulosa

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8
Q

Where in the nephron does aldosterone act ?

A

Collecting duct (principal cells)

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9
Q

Other than Angiotensin 2 what else can stimulate Aldosterone directly ?

A

Hyperkaelaemia

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10
Q

List 6 causes of hyperkalaemia ?

A

EXCESSIVE INTAKE - fasting, parenteral, stored blood transfusion

TRANSCELLULAR MOVEMENT - acidosis, DKA,rhabdomylosis

DECREASED EXCRETION - acute renal failure, CRF (late), K sparing diuretics (spironolactone), mineralocorticoid deficiency (Addisons), NSAIDs, ACEi, ARBs

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11
Q

Order these ECG changes based on severity of hyperkalaemia ?

Tall tented T waves
Broad QRS complex
Absent P waves
VF

A

Tall tented T waves > absent P waves > Broad QRS complex > VF

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12
Q

List 4 treatments of hyperkalaemia ?

A

10 mL 10% calcium Gluconate
100 mL 20% Dextrose with 10 units of insulin
Nebulised salbutamol
Calcium resonium PO

Insulin and salbutamol drive K+ into cells

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13
Q

How does Cushing’s disease cause hypokalaemia ?

A

The excess cortisol binds to the mineralocorticoid receptors on the nephron causing increased sodium reabsorption and increased potassium loss

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14
Q

List 6 causes of hypokalaemia ?

A
  1. GI loss
  2. Renal loss - hyperaldosteronism (high PB and low K+), increased sodium delivery to distal nephron (thiazide and loop diuretics), osmotic diuresis
  3. Redistribution into the cells - insulin, beta agonsists, metabolic alkalosis
  4. Rare causes - RTA type 1+2, hypomagnesaemia
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15
Q

Name the ion channels do K+ ions travel through to enter the tubule of the nephron ?

A

ROMK channels

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16
Q

List 2 causes of blockade/dysfunction of the Na+ k+ cl- triple ion transport channels in the ascending limb of the loop of henle ?

A

Loop diuretics
Bartter’s syndrome

This causes hypokalaemia
More sodium goes to the distal nephron and is reabsorbed there. This makes the tubule more negatively charged, causing K+ influx via ROMK channels.

17
Q

List 2 causes of blockade/dysfunction of the Na+cl- ion channels in the distal convoluted tubule ?

A

Thiazide diuretics
Gitelman syndrome

This causes more Na+ reabsorption in the distal part of the nephron. This causes increased negative charge of lumen. This causes influx of pottasium via ROMK channels.

18
Q

Which screening test can be used to diagnose primary Hyperaldosteronism in a patient with hypokalaemia and hypertension ?

A

Aldosterone: renin ratio

In primary hyperaldosteronism there is excess aldosterone which causes suppression of renin. This means you expect to see a high aldosterone: renin ratio

19
Q

List 3 clinical features of hypokalaemia ?

A

Muscle weakness
Arrhythmias
Polyuria + polydipsia (Nephrogenic DI)

20
Q

How is hypokalaemia treated ?

A

If serum k+ 3-3.5 mmol/L: Oral pottasium chloride (KCL)

If serum k+ <3 mmol/L: IV Pottasium chloride (KCL)

21
Q

How does ramipril cause hyperkalaemia ?

A

Ramipril inhibits ACE
This causes reduced conversion of AT1 to AT2
This causes reduced aldosterone
This means less K+ is excreted

22
Q

Where in the nephron is the defect in
A) Barter’s syndrome
B) Gitelman syndrome

A

A- Na+/K+/Cl- co-transporter Ascending limb of the loop of hence
B- DCT