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 ?
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
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 ?
- GI loss
- Renal loss - hyperaldosteronism (high PB and low K+), increased sodium delivery to distal nephron (thiazide and loop diuretics), osmotic diuresis
- Redistribution into the cells - insulin, beta agonsists, metabolic alkalosis
- Rare causes - RTA type 1+2, hypomagnesaemia
Name the ion channels do K+ ions travel through to enter the tubule of the nephron ?
ROMK channels