Chempath 13: Potassium And Electrolytes Flashcards
Which cells release renin ?
Junta-glomerular cells in the kidneys
What is the role of renin ?
Cleaves angiotensinogen to angiotensin 1
Which enzyme cleaves angiotensin 1 to angiotensin 2 ?
ACE
Where is ACE produced ?
The lungs
What is the role of angiotensin 2 ?
Stimulate adrenal cortex to produce aldosterone
Causes vasoconstriction
Stimulates the CNS to release ADH (vasopressin)
What causes renin release ?
Low sodium conc.
low perfusion pressure
Which section of the adrenal cortex produces aldosterone ?
Zona glomerulosa
Where in the nephron does aldosterone act ?
Collecting duct (principal cells)
Other than Angiotensin 2 what else can stimulate Aldosterone directly ?
Hyperkaelaemia
List 6 causes of hyperkalaemia ?
Renal failure Diabetic nephropathy (type 4 renal tubular acidosis) Spironolactone K+ sparing diuretics NSAIDs ACE inhibitor Addison’s (hypoaldosteronism) Rhabdomyolysis Acidosis
Order these ECG changes based on severity of hyperkalaemia ?
Tall tented T waves
Broad QRS complex
Absent P waves
VF
Tall tented T waves > absent P waves > Broad QRS complex > VF
List 4 treatments of hyperkalaemia ?
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
How does Cushing’s disease cause hypokalaemia ?
The excess cortisol binds to the mineralocorticoid receptors on the nephron causing increased sodium reabsorption and increased potassium loss
List 6 causes of hypokalaemia ?
Diarrhoea and vomiting Cushing’s syndrome Insulin Beta agonists Alkalosis renal tubular acidosis type 1 and 2 Hypomagnesaemia
Name the ion channels do K+ ions travel through to enter the tubule of the nephron ?
ROMK channels
List 2 causes of blockade/dysfunction of the Na+ k+ cl- triple ion transport channels in the ascending limb of the loop of henle ?
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.
List 2 causes of blockade/dysfunction of the Na+cl- ion channels in the distal convoluted tubule ?
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.
Which screening test can be used to diagnose primary Hyperaldosteronism in a patient with hypokalaemia and hypertension ?
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
List 3 clinical features of hypokalaemia ?
Muscle weakness
Arrhythmias
Polyuria + polydipsia (Nephrogenic DI)
How is hypokalaemia treated ?
If serum k+ 3-3.5 mmol/L: Oral pottasium chloride (KCL)
If serum k+ <3 mmol/L: IV Pottasium chloride (KCL)
How does ramipril cause hyperkalaemia ?
Ramipril inhibits ACE
This causes reduced conversion of AT1 to AT2
This causes reduced aldosterone
This means less K+ is excreted
Where in the nephron is the defect in
A) Barter’s syndrome
B) Gitelman syndrome
A- Na+/K+/Cl- co-transporter Ascending limb of the loop of hence
B- DCT
