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Diuretics

Applied Sciences Lecture Course. Diuretics. Dr Cathy Armstrong SpR In Anaesthesia & Clinical Fellow in Undergraduate Medical Education Manchester Royal Infirmary March 2011. Aims & Objectives. Define the term diuretic Classify diuretics into groups Describe mechanisms of action

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Diuretics

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  1. Applied Sciences Lecture Course Diuretics Dr Cathy Armstrong SpR In Anaesthesia & Clinical Fellow in Undergraduate Medical Education Manchester Royal Infirmary March 2011

  2. Aims & Objectives Define the term diuretic Classify diuretics into groups Describe mechanisms of action Describe relevant pharmacokinetic aspects Discuss common clinical uses

  3. What is a diuretic?

  4. What is a diuretic? An agent that promotes excretion of urine

  5. In the glomerulus where is the majority of sodium reabsorbed? • Proximal convoluted tubule • Loop of Henle • Distal convoluted tubule • Collecting duct

  6. Cvpharmacology.com

  7. Which of these is NOT a class of diuretic? • Loop diuretic • Carbonic anhydrase inhibitor • Sodium-sparing diuretic • Potassium-sparing diuretic • Thiazide diuretic

  8. Cvpharmacology.com

  9. Thiazide diuretics Main action on distal convoluted tubule Bendroflumethazide hydrochlorothiazide Inhibit sodium & chloride reabsorption www.mc.uky.edu

  10. Thiazide diuretics Maximal effects produced by small doses Duration of action 12-18 hours Side effect profile Hypokalaemia Particular caution with digoxin Increased uric acid levels Impaired glucose tolerance Increased cholesterol levels

  11. Cvpharmacology.com

  12. What is the commonest clinical use of thiazide diuretics? • Heart failure • Hypertension • Cerebral oedema • Renal failure

  13. Hypertension • Thiazide diuretics • ↓ systolic BP by 10-15 mmHg • ↓ diastolic BP by 5-10 mmHg

  14. Hypertension MAP = CO x SVR CO = HR x SV Preload Contractility Afterload ~ 1 r4

  15. Hypertension MAP = CO x SVR CO = HR x SV Preload Contractility Afterload ~ 1 r4

  16. Hypertension MAP = CO x SVR CO = HR x SV Preload Contractility Afterload ~ 1 r4

  17. Hypertension – NICE guidance A = ACE inhibitor, C = calcium channel blocker, D = thiazide diuretic

  18. Loop diuretics Act on thick ascending limb of loop of Henle Sodium-potassium-chloride cotransporter Handles 25% of sodium reabsorption www.mc.uky.edu

  19. Loop diuretics Induce renal synthesis of prostaglandins ↑ renal blood flow Redistribution of renal cortical blood flow Quick onset, shorter duration of action

  20. Loop diuretics Side effects Hypokalaemia Hyperglycaemia & hyperuricaemia Transient damage to CN VIII (esp with gentamycin) Uses Pulmonary oedema (Acute LVF) Chronic heart failure Hypertension Peripheral oedema

  21. Cvpharmacology.com

  22. Pulmonary oedema • Presentation • Dyspnoea • Hypoxia • Sweating • Tachycardia (gallop rhythm) • Elevated JVP • Pink frothy sputum • Crepitations on auscultation of lung fields

  23. Pulmonary oedema • Immediate management • Oxygen • Sit patient up • IV access • Furosemide (40 – 80mg IV) • Diamorphine • GTN infusion (if BP will tolerate) • Consider CPAP

  24. Pulmonary oedema Cvpharmacology.com

  25. Chronic Heart Failure – NICE Guidance

  26. Potasium sparing diuretics Block sodium channels distal end of DCT www.mc.uky.edu

  27. Potasium sparing diuretics • Weak diuretics • Examples • Amiloride, Triamterene • Often co-administered to reduce hypokalaemic effects of loop / thiazides • Co-amilofruse • Co-triamterzide • Side effects • hyperkalaemia

  28. Aldosterone Antagonists Spironolactone Aldosterone enhances expression of sodium channel in distal end of DCT

  29. Cvpharmacology.com

  30. Aldosterone Antagonists Uses Oedema & ascites in cirrhosis of the liver Chronic heart failure Primary hyperaldosteronism Conn’s syndrome side effects Hyperkalaemia N&V gynaecomastia

  31. Carbonic anhydrase inhibitors Prevent reabsorption of bicarbonate in proximal convoluted tubule www.mc.uky.edu

  32. Carbonic anhydrase inhibitors • Weak diuretics • Not used for diuretic properties • Uses • Prophylaxis against altitude sickness • glaucoma

  33. Osmotic diuretics Mannitol Draws water from the extracellular & intracellular spaces into the vascular compartment Easily filtered but not reabsorbed Continues to be osmotically active in tubules causing diuresis Main use Cerebral oedema

  34. Diuretics in acute renal failure?

  35. Summary Cvpharmacology.com

  36. ?

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