diuretics

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Ambestul
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12294
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diuretics
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2010-03-31 08:33:56
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renal quiz 4
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diuretics
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  1. peripheral edema detected when:
    interstitial fluid increases by 2 1/2-3L
  2. 1+ pitting
    2mm, trace
  3. 2+ pitting
    4 mm, moderate-disappears in 10-15 seconds
  4. 3+ pitting
    6 mm, deep-disappears in 1-2 minutes
  5. 4+ pitting
    8 mm, very deep-disappears in 5 minutes
  6. treatment for edema
    treat underlying cause, supportive treatment, sodium restriction, diuretics
  7. supportive treatment
    first line for pts with edema secondary to DVT or overproduction of lymph fluid

    • a. Avoid prolonged standing or inactivity
    • b. Elevate edematous legs
    • c. Avoid placing hard objects under the knees when reclining
    • d. Avoid constricting clothing, including tight-fitting or high-heeled shoes
    • e. Avoid alcohol and excessive heat
    • f. Support hosiery
  8. sodium restriction
    DASH diet <2400mg sodium, one tea NaCl tablet salt contains 2000 mg sodium
  9. when are diuretics indicated?
    when edema persists despite supportive therapy and sodium restricted
  10. carbonic anhydrase inhibitors
    • ex: acetazolamide
    • Use:

    • • Diuretic (rarely)
    • • Glaucoma (↓ IOP)
    • •Metabolic Alkalosis
    • •Altitude Sickness
  11. osmotic diuretics
    • ex: mannitol
    • Use:

    • • Diuretic (rarely)
    • • Cerebral edema
    • • ↓ Intracranial pressure
  12. loop diuretics
    • most potent diuretic
    • ex: bumetanide, furosemide, torsemide
    • use:

    • • Diuretic
    • • Hypercalcemia
    • • Pulmonary Edema
    • • RTA
  13. thiazide diuretics
    • moderate diuretic activity
    • ex: chlorothiaz, HCTZ, chlorthal, indapamide, metolazone
    • use:

    • • Diuretic
    • • Hypertension
    • • Hypercalciuria
    • • Diabetes insipidus
  14. potassium sparing (PSD)
    • least potent
    • ex: amiloride, triamterene, spironolactone, eplerenone
    • use:

    • • Diuretic
    • • K loss
    • • Cirrhotic ascites
    • • CHF (spironolactone, eplerenone
  15. hypokalemia occurs with which diuretics
    • loops and thiazides
    • associated with: dose, worse with long-acting, high sodium intake
  16. strategies to prevent diuretic induced hypokalemia
    • 1. use smallest dose poss
    • 2.restrict Na
    • 3. encourage k-rich foods ( can prevent but not treat if metabolic alkalosis K citrate in foods is converted to bicarb
    • 4. subst or add k-sparin
    • 5. recomm a salt subst 10 mEq K/gm
    • 6.rx an oral k supp 20 mEq/day
    • 7. add an ACE or ARB
  17. Loops IV/PO-special clinical concerns
    • **PO is 2x the IV dose
    • a. F varies with product
    • • Toresemide (Demedex ®) ~80-100%
    • • Bumetanide (Bumex ®, generics) ~80-90%
    • • Furosemide (Lasix ®, generics) ~10-100% (50%)
    • b. Duration of Action – 2-3 hours
    • c. High Ceiling Effect
    • d. Dosing: Start with 20 mg furosemide PO (or equivalent). If inadequate response, double the dose
    • sequentially until response ensues or max dose reached.
  18. 1 mg bumetanide=
    40 mg furosemide IV=80 mg PO
  19. ototoxicity
    furosemide-doses greater than or equal to 100 mg IV, rapid inf time and worse with other drugs causing ototox, AGs and vanco
  20. inf time of furosemide NFT
    4mg/min
  21. short DOA-thiazides
    6-12 hours chlorthiazide, HCTZ
  22. medium DOA-thiazides
    12-24 hours, metolozone
  23. long DOA-thiazides
    >24 hours, chlorthaiidone, indapamide
  24. ceiling effects of loops and thiazides
    • loop-high ceiling effect
    • thiazides-low
  25. Specific Clinical Concerns of thiazides
    • a. ineffective when CrCl <30ml/min
    • b.Hyponatremia -part. in elderly
    • c.Hyperuricemia -also with loops but worse
    • d.Hypercalcemia (rarely) -calcium-sparing, good for post-menopausal
    • e.Hyperglycemia -still first line in HTN
    • f. ↑ Serum Lithium levels • Pancreatitis
  26. Spironolactone
    • aldosterone antag
    • plateu effect not reached til 3-4 days
    • dose 25-100 mg qd x 5 days, titrate up to 200mg/day
  27. Eplerenone
    Inspra

    • Selective Aldosterone antagonist
    • • Plateau effect – max effect not seen for 4 weeks
    • ¾ Dose: 25 mg q day x 4 weeks. Titrate upwards to 100 mg daily
  28. Triamterene
    • Dyrenium,
    • (+ HCTZ = Dyazide ® 37.5 /25 & 50/25 , Maxide -25® 37.5/25
    • Maxide ® 75/50 )
    • d. Amiloride (Midamor ® )
    • e. Specific Clinical Concerns
    • ¾ Hyperkalemia
    • ¾ Hyponatremia (spironolactone, eplerenone)
    • ¾ Gynecomastia (spironolactone)
    • ¾ Nephrolithiasis & Nephrocalcinosis (triamterene)
  29. Maintaining diuretic efficacy
    • a. Na restriction-cornerstone, Na overrides effect of diuretic
    • b. Avoid drugs that interfere with diuretic effectiveness
    • c. Dose -short-acting max diuresis within a few hours, can increased.
    • d. Route-HF Gi abs decreased due to excess fluid in gut, take on empty stomach, or switch to higher F or continous IV
  30. maximizing diuretic safety
    • rate of diuresis:
    • -initial fluid loss-intravascular space-refilled by fluid mobilized in interstium, rate should not exceed rate of mobilization or will be hemodynamically unstable, goal: 1-2 lbs/24 hours, except ascites assoc with cirrhosis, slower movement more gradual 0.5-1 lbs/day
  31. monitoring of diuretic use
    • vitalsigns
    • • Weight
    • • BUN:Cr ratio (~ 10-20:1)
    • • GFR
    • • Potassium
  32. diuretic resistance
    Failure to ↓ interstitial fluid volume despite liberal use of diuretics and sodium restriction
  33. Increased sodium reabsorption
    • -nephron adaptation to chronic therapy
    • • Drugs (NSAIDs) Potential solutions
    • • Sequential nephron blockade
    • • DC offending agents
  34. Reduced renal blood flow
    • due to drugs (NSAIDs)
    • potential soln
    • d/c offending agents
  35. insufficient concentration of diuretic at site of action
    increase dose or more freq admin or cont infusion
  36. cont infusion of loop diuretics
    to maintain threshold conc at all times, can see increase with same dose

    • Sample protocols – most suggest a bolus dose of 40-80 mg IV furosemide followed by continuous
    • infusion furosemide 250 mg in 250cc D5W @:
    • • 0.05 – 0.1 mg / Kg / hr – titrate ↑ to goal UOP (CHF 2002;8(2):80-85) -or -
    • • Start @ 0.1 mg/Kg/hr - ↑ hourly by 0.1 mg/kg/hr to a max rate of 0.75 mg/kg/hr (Crit Care Med
    • 1997;25:1969-1975) - or -
    • • NEJM 1998;339(6):387-395
    • J. Diuretic Challenges
    • 1. Ascites associated with cirrhosis
    • a. Diuretic
  37. Ascites associated with cirrhosis
    • -diuretic challenges:
    • • Secondary hyperaldosteronism causes sodium & water retention
    • • Rapid diuresis may compromise intravascular volume
    • • ↓ renal tubular responsiveness to diuretics b. Therapeutic Approach
    • • Spironolactone 100-200 mg / day administered with food
    • • If inadequate response, add low dose Metolozone or Indapamide prn
  38. Chronic Heart Failure
    • -diuretic challenges:
    • • Impaired oral absorption of furosemide
    • • ↓ renal tubular responsiveness to diuretics b. Therapeutic Approach
    • • Give moderate doses of loop diuretic more frequently
    • • If inadequate response, add a thiazide in doses appropriate for renal function
  39. Renal failure
    • -diuretic challenges:
    • • Impaired delivery of diuretic to renal tubule
    • • ↓ filtered load of sodium in response to ↓ GFR b. Therapeutic Approach
    • • Give increasing doses of loop diuretic up to 160-200 mg furosemide IV bolus (or equivalent)
    • • If inadequate response, add Metolazone or Indapamide
    • • If diuresis still inadequate, continuous infusion of loop diuretic
  40. Nephrotic syndrome
    • >3gm, protein spills into urine
    • a. Diuretic Challenges
    • • Impaired delivery of diuretic to renal tubules secondary to binding to urinary protein
    • • ↓ renal tubular responsiveness to loop diuretics
    • • ↑ proximal or distal reabsorption of sodium
    • b. Therapeutic Approach
    • • Give larger doses (2-3 x normal) of loop diuretic
    • • Administer diuretic more frequently
    • • If inadequate response, add thiazide
  41. drug-induced edema
    • diuretics less effective for treating
    • recommend alternatives to drugs that are causing the edema

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