Acute renal failure

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Author:
bigfootedbertha
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84755
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Acute renal failure
Updated:
2011-05-09 11:59:08
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nephrology
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for my upcoming nephrology exam
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  1. What is the definition of acute renal failure?
    Worsening of kidney function over hours to days, resulting in the retention of nitrogenous waste and Cr in the blood, creating an inability to maintain acid-base, fluid, and electrolyte balance
  2. What is azotemia?
    Retention of nitrogenous wastes (urea nitrogen) and Cr in the blood
  3. What is oliguria?
    Urine output <500cc/day or <20cc.hour
  4. What is anuria?
    Urine output <20cc/day
  5. What is the RIFLE criteria?
    • Risk
    • Injury
    • Failure
    • Loss
    • ESRD
  6. Which RIFLE classes are associated with an increased risk for in-hospital mortality?
    • Injury
    • Failure
  7. What is pre-renal failure?
    Decreased renal perfusion leading to lower GFR, renal parenchyma is NOT damaged
  8. What is the msot common cause of renal failure?
    Pre-renal failure
  9. What causes pre-renal failure?
    • Kidneys not seeing enough arterial volume
    • Decreased circulating volume due to GI loss, dehydration, hemorrhage, pancreatitis, burns, and excessive diuresis
    • Low CO (CHF, cardiac tamponade, massive PE, cardiogenic shock)
    • Altered system resistance: sepsis, anaphylaxic, cirrhosis (systemic vasodilation)
  10. What are clinical features of pre-renal failure?
    Signs of dehydration
  11. Describe labs in a pre-renal pt:
    (Urine Na, FeNa, BUN/Cr, UA)
    • Urine Na <20 (body is holding onto it to hold water)
    • FeNa<1%
    • BUN/Cr>20:1 (reflection of hemoconcetration, people are dry)
    • UA; benign or hyaline casts
  12. What is FeNa?
    Fractional excretion of Na, used to help ascertain etiology of renal failure
  13. What is the FeNa forumula?
    (Urine Na/Plasma Na)/(Urine Cr/Plasma Cr)
  14. When is FeNa most helpful? (Oliguric or non-oilguric)
    Oliguric states
  15. What can alter a FeNa measurement?
    • Use of diuretics in the past 12-24 hours
    • Acute glomerulonephritis
    • Therefore use urine urea for UNa
  16. What are the FeNa classes?
    • <35%: prerenal
    • >35%: intrinsic
  17. How do you tx pre-renal failure?
    • Replete volume
    • Low CO: inotropes (dobutamine), pericardiocentesis, lytics
    • Dec SVR: Replete vascular volume, add vasoconstrictor (Norepi)
    • Monitor lytes, avoid nephrotoxins
  18. When might pre-renal failure not correct quickly?
    When ischemia has occured, which may progress to ATN
  19. What is intrinsic renal failure?
    Dz of the kidney itself, affecting mostly the glomerulus or tubule, renal parenchyma IS damaged
  20. Name 4 causes of intrinsic renal failure
    • Obstruction
    • Dz of glomeruli or microvasculature (Glomerulonephritis and vasculitis, TTP/DIC/Hemolytic uremic syndrome)
    • ATN (ischemia caused by hypotension, Toxins)
    • Acute Interstitial Nephritis
  21. What things can cause renovascular obstruction in intrinsic renal failure?
    • Atherembolic (cholesterol crystals)
    • Renal artery thrombosis
    • Renal artery dissection (stenotic or occlusive lesions)
  22. What puts a person at risk for atheroembolic obstruction?
    • >50 yo
    • Hx of recent manipulation of the aorta
    • HTn
    • anticoagulated pts
  23. What are clinical findings of a pt with intrinsic renal failure caused by atherosclerosis?
    • Livedo reticularis
    • Gangrenous toes
    • UA nl (may see casts or eosinophilia)
    • Low completement levels
  24. How do you tx intrinsic renal failure caused by atherosclerosis?
    No tx has been proven efficacious
  25. What predisposes someone to renal artery thrombosis?
    Hx of afib, recent AMI
  26. What are clinical findings of someone with intrinsic renal failure caused by renal artery thrombosis?
    • Flank pain
    • hematuria
    • elevated LDH
    • nl transaminases
  27. How do you tx someone with intrinsic renal failure caused by renal artery thrombosis?
    Anticoagulation
  28. What predisposes someone to renal artery dissection?
    HTN pts with underlying atherosclerotic, firbomuscular dysplasia
  29. What are the m/c causes of glomerulonephritis?
    • Post infectious GN due to GABHS#1
    • Goodpastures #2
  30. What are sx of malignant HTN?
    • HA,
    • pulmonary edema,
    • neurologic dysfunction
  31. What does UA show in malignant HTN?
    • red cells and red cell casts
    • protein
  32. What can cause ischemic ATN?
    • Sepsis
    • Prolonged hypotension
    • Hemorrhage
    • cardiac arrest
  33. When is the liklihood of ischemic ATN increased?
    When renal failure persists after restoration of BP
  34. muddy brown granular casts
    • Ischemic ATN
    • Toxin induced ATN
  35. What does a U/A show lab wise in an ischemic ATN pt?
    BUN/Cr
    FeNa
    UNa
    SG
    • BUN/Cr <20:1
    • FeNa >1%
    • UNa >20
    • SG < 1.015
  36. How do you tx ischemic ATN?
    • Restore perfusion and maintain BP
    • Avoid nephrotoxins, tx electrolytes
    • Dialysis if needed
  37. What is the med class most commonly causing toxin-induced ATN?
    Aminoglycosides
  38. When does contrast nephropathy occur?
    24-48 hours after receiving dye, peaks 3-5 days, resolives in 1 week
  39. How can you prevent contrast dye nephropathy?
    • Hydration, pretreatment with mucomyst or HCO3 contianing IVF
    • Results mixed
  40. What other meds aside from aminoglycosides can acuse ATN?
    • Cisplastic
    • Acyclovir
    • Cyclosporine
    • Carboplatin
    • Tacrolimus
    • Amphotericin
    • ACE-I
    • Bactrim
  41. What do labs show in toxin-induced ATN?
    • BUN/Cr <20:1
    • FeNa > 1%
    • UNa >20
  42. What can cause myoglobinuria?
    • Crush injuries
    • Seizures
    • Alcohol
    • Prolonged unconsciousness
    • Burns
    • Cocaine
    • Statins
    • Infection
  43. What are signs/sx of myoglobinuria?
    • Weakness, pain, edema in affected muscles
    • N/V/confusion, arrhythmias
    • severe cases: hypotension, DIC, shock, compartment syndrome
  44. Tea colored urine
    Rhabdo
  45. What do rhabdo pts' labs look like?
    • CK>10,000
    • Hyperkalemia, hyperphosphatemia, hyperuricemia
    • Hypocalcemia (it's deposited in the muscle)
  46. How do you tx rhabdo pts?
    • Fluids!
    • Goal UO: 1.5cc/kg/hr
    • Can use loops to ensure good urine output (even though you are flushing pt with fluids)
  47. What causes hyperuricemic renal failure?
    Tumur lysis syndrome
  48. Who gets hyperuricemic renal failure?
    • pts with high cellular burden following chemo (1-3 days)
    • NHL, leukemia
  49. What is hyperuricemic renal failure?
    Rapid relase of tumor cellular markers that overwhelm metabolic pathways that cause tubular obstruction and ARF
  50. What are s/sx of hyperuricemic renal failure?
    • Weakness, lethargy
    • N/V
    • Muscle cramps, tetany
    • Fluid overload
    • Arrhythmias
  51. What does hyperuricemic renal failure labwork show?
    • Same as rhabdo
    • Hyperkalemia, phosphatemia, and uricemia
    • Hypocalcemia
  52. How do you tx hyperuricemic renal failure?
    • Vigorously hydrate
    • Allopurinol (prevents further high levels of uric acid)
    • Rasburicase (lowers level of uric acid)
    • Urinary alkalizatoin with metabolic acidosis
    • Tx electrolytes
  53. What is acute interstitial nephritis?
    Infiltration of tubulointerstitium by granulocytes (eosinophils) and macrophages
  54. What is the m/c cause of acute interstitial nephritis?
    • Drugs
    • PCNs
    • Cephs
    • NSAIDs
    • PPI
    • Bactrim
    • Rifampin
  55. What infections can cause acute interstitial nephritis?
    • Legionella
    • Leptospirosis
    • Streptococcal
  56. What are clinical findings of acute interstitial nephritis?
    • Acute/subacute N/V/ malaise,
    • fever, maculopapular rash
    • Triad: fever, rash, eosinophils
  57. What does a U/A show in a acute interstitial nephritis pt?
    • White cells, white cell casts, red cells
    • Eosinophiluria (>1% of WBC cells on Hansel stain)
  58. What is the gold standard for dx acute interstitial nephritis?
    renal biopsy, only done in severe cases
  59. How do you tx acute interstitial nephritis?
    • D/c offending agent and monitor
    • Sever cases: short corse of steroids
  60. What are mortality rates like in acute interstitial nephritis?
    20-50% in hospital, 70% with comorbid illness
  61. What is postrenal failure?
    Urinary flow from B/L kidneys are obstructed, or a single functioning kidney is obstructed
  62. What is the m/c cause of postrenal failure?
    prostatic dz
  63. Describethe course of GFR in postrenal failure
    Increases then decreases
  64. What are s/sx of postrenal failure?
    The same for BPH/what you would expect for an obstruction
  65. What do postrenal failure labs show?
    • Early: resemble prenal (low FeNa and Una, high urine osm) as tubules aren't damaged
    • Later: (tubules damaged, can't concentrate urine)
    • BUN/Cr >20:1
    • UNa >20
    • Low Uosm
  66. What is the best way to image postrenal failure?
    • renal ultrasound
    • NON CONTRAST Ct if needed
  67. How do you tx postrenal failure?
    • Place foley
    • Relieve obstruction
    • After obstruction resolved, expect post-obstruction Diuresis and hydrate to avoid volume depletion
  68. What are complications of ARF?
    • Hyponatremia
    • Hyperkalemia
    • Arrhythmias
    • Hyperphosphatemia
    • Hypocalcemia
    • Metabolic acidosis
    • Hypermagnesmia
  69. What are sx of uremia?
    • Cardiac pericarditis
    • Asterixis, confusion, coma, seizures
    • Bleeding diathesis
    • Infection
    • N/V/bleeding
    • Pruritus
  70. What are the indications for dialysis?
    • AEIOU
    • Acidosis
    • Electrolyeimbalance (hyperkalemia, not mag, phos, etc)
    • Ingestions (ASA, methanol)
    • O: volume overload
    • U: uremia causing end-organ damage (pericarditis, encephalopathy)
  71. What is general tx of ARF?
    • Avoid nephrotoxins
    • Adjust meds to GFR
    • Anticipate changes in electrolytes and tx accordingly
    • Consult renal in a timely fashion

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