Treating Fluid Overload Flashcards
What is the mechanism of action of loop diuretics?
They bind to NKCC transporters in the Thick ascending limb of the loop of henle.
This inhibits Cl- reabsorption so diminishes electrochemical gradient so reduces Na+ reabsorption.
This reduces the ability of the kidney to generate the corticomedullary concentration gradient so loop diuretics have a BIG effect.
When are loop diuretics used clinically?
Marked oedema in heart failure, nephrotic syndrome, hepatic cirrhosis.
What is the therapeutic effect of loop diuretics?
Diuresis. Natriuresis. Short lived venodilation.
What are the adverse effects of loop diuretics?
HYPOKALAEMIA Alkalosis Gout Dilutional hyponatraemia Ototoxicity Increased LDL and TG Hypotension.
What is the mechanism of action of thiazide diuretics?
Inhibition of NaCl transporter of distal convoluted tubule.
What are the therapeutic effects of thiazide diuretics?
Less diuresis than loop diuretics
Reduce urinary Ca2+ loss by inhibiting Ca2+ transport in proximal and distal tubules.
Thiazides produce arterial vasodilation during long term use so have hypotensive effect
What are the adverse effects of thiazide diuretics?
HYPOKALAEMIA
HYPONATRAEMIA
HYPERURICAEMIA
HYPERCALCAEMIA
Glucose intolerance
Hyperlipidaemia
Impotence
Nocturia and urinary frequency.
What are the adverse drug reactions of thiazide diuretics?
Beta blockers- exacerbate hyperglycaemia, hyperlipidaemia, hyperuricaemia
Carbamazepine- increased risk of hyponatraemia
Steroids- increased risk of hypokalaemia
What is the mechanism of action of potassium sparing diuretics?
Act at late DCT and cortical collecting duct. They act at the ENaC channel. They cause reduced Na+ reabsorption which limits NaK ATPase so less K+ is lost.
What is the mechanism of action of spironolactone?
Does not act at luminal membrane of tubular cells. Competes with aldosterone to downregulate ENaC. So very effective in hyperaldosteronism.
What are the DDIs of potassium sparing diuretics?
ACE inhibitors- can cause hyperkalaemia
What are the unwanted effects of potassium sparing diuretics?
GI disturbance
Hyperkalaemia
Hyponatraemia
Antiandrogenic effect causes gynaecomastia and impotence, menstrual irregularities.
What is the management for hyperkalaemia?
Treat the cause-reduced urine loss, excess intake, tissue damage, acidosis, drugs eg ACEi, NSAIDs, ENaC blockers
Carry out ECG
Protect the heart- calcium gluconate
Lower serum K+- insulin/dextrose
Remove K+ from body- calcium resonium.
What are the ECG changes of hyperkalaemia?
Tall T waves, small or absent P waves, increased P-r Interval, wide QRS.
Sine wave pattern (peri-arrest)
Asystole
