deck_1660749 Flashcards
Define diuresis
• Increased formation of urine by the kidney
Define diuretics
• Block reabsorption of Na+ and therefore water by the kidney
Give three main types of diuretics
• Loop diuretics • Thiazide diuretics • K+ sparing diuretics and aldosterone antagonists
How do loop diuretics work?
• Acts on TAL of the loop of henle • Block Na-K-2Cl • Causes excretion of 10-25% of filtered Na+ ions (segments downstream also have limited capacity to reabsorb water, increasing diuresis)
Name two loop diuretics
• Furosemide • Bumetanide
What do Thiazide diuretics do?
• Act on early DCT • Block Na-Cl co-transporter • Inhibits only 5% of Na+ reabsorption
Give a thiazide diuretic
• Bendroflumethiazide
Where do K+ sparing diuretics and aldosterone antagonists work?
• Late DCT and collecting duct • Reduce ENaC reabsorption of sodium • Inhibit 2% Na+ reabsorption
Why are K+ sparing diuretics named thus?
Reduce the loss of K+ and can produce life threatening hyperkalaemia
Give an example of a K+ sparing diuretic
• Amiloride
Give an example of an aldosterone antagonist
• Spironolactone
Give overall dangers of diuretics
• Hyper/hypokalaemia • RAAS activation
Outline the negatives of using K+ sparing diuretics/Aldosterone Antagonists
• Reduce loss of K+ and may produce life threatening hyperkalaemia
Give a negative effect of loop diuretics
• Reduces calcium absorption, inducing urinary excretionPatient may become hypocalcaemi
What do loop and thiazide diuretics do?
• Increase the loss of potassium in the urineHypokalaemia
Outline how loop and thiazide diuretics cause hypokalaemia
• Block Na+ and H20 reabsorption in LoH or early DCT • Increase Na+ and H20 delivery to late DT + CD • Increase Na+ absorption by principle cells/Faster flow rate of filtrate so K+ washed away faster • Favourable electrical gradient for K+ excretion/Low K+ concentration in lumen
How do K+ sparing diuretics cause hyperkalaemia?
• Block epithelial Na+ channels • Reduce Na+ reabsorption • Reduce potassium loss in urine • Hyperkalaemia
How do aldosterone antagonists cause hyperkalaemia?
• Block of action of aldosterone • Reduce activity of Na/K+ ATPase & epithelial Na+ channels • Reduce Na+ reabsorption • Reduce potassium loss in urine • Hyperkalaemia
What do all diuretics do?
• Reduce ECF volume so activate RAAS • This increases aldosterone secretion, increase Na+ reabsorption and K+ secretion, contributing to hypokalaemia
List negative effects which come about as a result of diuretics use and abuse
• Hypokalaemia • Hyperkalaemia • RAAS activation • Hypovolaemia • Hyponatraemia • Increased uric acid levels in blood • Metabolic effects
What is hypovolaemia?
• Decreased ECF volume due to excessive loss of Na+ and water
What 3 things must be done to avoid hypovolaemia?
• Monitor weight • Look for signs of dehydration • Check BP
What is hyponatraemia?
• Decreased sodium in bloodMultiple symptoms, including nausea, vomiting, headache and confusion
What do increased uric acid levels in blood cause?
Gout
What are two negative metabolic effect of diuretic use?
• Glucose intolerance • Increased LDL levels
What is a carbonic anhydrase inhibitor?
• Diuretic which acts in PCT by inhibitng enzyme carbonic anhydrase to interfere with Na+ and HCO3- reabsorption
Why is carbonic anhydrase no longer used a diuretic?
• HCO3- loss leads to metabolic acidosis
Give six conditions diuretics used to treat
• Conditions with ECF expansion and Oedema • Acute pulmonary oedema • Hypertension • Hypercalcaemia • Cerebral oedema (Osmotic diuretics) • Glaucoma (carbonic anydrase)
Give four conditions which involve ECF expansion and oedema
• Congestive heart failure • Nephrotic syndrome • Kidney failure • Ascites and oedema due to liver cirrhosis
What is acute pulmonary oedema usually due to?
• Left heart failure
What is pulmonary oedema treated with?
• Loop diuretics
What is hypertension treated with?
• Thiazide diuretics • Spironolactone in primary hyperaldosteronism (Conn’s syndrome)
How is hypercalcaemia treated?
• Loop diuretics promote Ca2+ excretion in loop of henle
Give three substances with diuretic actions
• Alcohol - Inhibits ADH release • Coffee - Increased GFR, decreased Na+ reabsorption • Lithium - Inhibits ADH action on collection ducts
What is diuresis expressed as in the form of a symptom?
• Polyuria
Give four causes of polyuria that are non drink related
• Diabetes mellitus ○ Glucose in filtrate -> Osmotic diuresis • Central diabetes insipidus ○ Decreased ADH release from posterior pituitary -> Diuresis • Nephrogenic diabetes insipidus ○ Poor response of collecting ducts to ADH -> Diuresis • Psychogenic polydypsia ○ Increased intake of fluid
