Flashcards in Diuretics and Renal Replacement Therapy Deck (65)
What is a diuretic?
A substance/drug that promotes diuresis
(Increased renal excretion)
What percentage is the normal fractional excretion of Na+?
Less than or equal to 1%
Aldosterone increases the expression of which channels/transporters?
How do loop diuretics work and give an example?
Act on the loop of Henle
Block NKCC2 cotransporter
How do thiazides work and give an example?
Act on early DCT
Block NaCl cotransporter
How do K+ sparing diuretics work and give an example?
Act on late DCT and CD
Block ENaC channels
How do aldosterone antagonists work and give an example?
Competitive inhibition of aldosterone on principle cells in late DT and CD
How does mannitol work?
Use small molecules to increase osmolarity of filtrate
Increased water excretion (decreased water reabsorption)
How are carbonic anhydrase inhibitors used as a diuretic?
Prevents uptake of bicarbonate as it cannot from water and CO2 to enter the cells
However can lead to metabolic acidosis due to all the bicarbonate in the urine
How do loop diuretics affect magnesium and calcium?
Magnesium and calcium reabsorption rely on the gradient of the thick ascending limb LOH
Therefore loop diuretics inhibit their reabsorption
Increased loss of calcium and magnesium
Can cause hypocalcaemia and hypomagnesiumia
Why are loop diuretics chosen to help heart failure failure and acute pulmonary oedema?
They are very potent diuretics
What can we use loop diuretics to treat?
Why are thiazides good diuretics for the elderly?
Blocking Na+ reabsorption increases the Ca2+ reabsorption
Good for the elderly who are prone to osteoporosis
Why are thiazides ineffective in renal failure?
Less potent as only 5% sodium reabsorption inhibited
What are thiazides widely used for and why?
Decreased effective circulating volume and cause vasodilation
What is the potential problem when using thiazides?
Why are K+ sparing diuretics often a bad choice?
Mild diuretics therefore cannot cope with large volume increases
Can produce severe hyperkalaemia esp if used in conjunction with ACEi, K+ supplements or in pts with renal failure
What is the preferred drug to treat ascites and oedema in cirrhosis?
Which diuretics are often used in conjunction for heart failure?
Why do we have to be careful when using diuretics?
Decreased circulatory volume and reduce perfusion pressure to the kidneys
This can activate RAAS
Causes water retention (counter productive)
Describe nephrotic syndrome
Increase in glomerular BM permeability to proteins
Low plasma albumin - decreased oncotic pressure - oedema
What is ascites?
Free fluid in the peritoneal cavity
Describe hepatic encephalopathy
Reversible syndrome of impaired brain function
Occurs in cirrhosis with advanced liver failure
Causes confusion and comas
Signs - constructional apraxia (cannot draw a 5 pointed star) and flapping tremors
Includes elevated ammonia levels in blood
Hypokalaemia can cause this
Name some adverse effects of diuretics
Decreased blood volume - postural hypotension, dehydration
Increased uric acid levels - gout
Erectile dysfunction (thiazides)
How can alcohol affect blood volume levels?
Inhibits ADH release
How does coffee affect the kidney?
Decreased Na+ reabsorption
Increased loss of Na+ and water
Define end stage renal failure (ESRF)
When death is likely without renal replacement therapy
eGFR < 15 ml/min
Give some symptoms/signs of ESRF
Tiredness - overwhelming fatigue physically and mentally
Volume overload - oedema, SoB
Sexual dysfunction/reduced fertility
What percentage of patients with CKD are hypertensive?