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What is ATN?
- Acute kidney injury from ischemia or toxin
- Ischemia frmo hypoperfusion or hypoxemia
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What causes ATN?
Shock, sepsis, or hypovolemia
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What are the three phases of ATN?
- Initial (injury)
- Maintenance (Lasts 1-3 weeks to a couple of months): cellular repair is starting to occur, removal of any tubular debris or necrotic materials
- Recovery: diuresis occurs, BUN and Cr fall, GFR increases
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Name 3 exogenous nephrotoxins causing ATN
- Aminoglycosides
- Contrats
- Cyclosporines
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Name 4 endogenous nephrotoxins causing ATN
- Myoglobinuria
- Hemoglobin
- Hyperuricemia
- Bence Jones proteins
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What increases the risk for aminoglycosides causing ATN?
- Age
- Underlying kidney dz
- Hypovolemia
- Age
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What is the least nephrotoxic aminoglycoside?
Streptomycin
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When does aminoglycoside toxicity occur and how long does it last?
5-10 days after exposure, and can be present in renal tissue for one month
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When does contrast toxicity occur?
Within 24-48 hours of study
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How can you prevent ATN caused by contrast?
- N-acetylcystine
- HCO3
- Avoiding contrast
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How does cyclosporine cause ATN?
- It causes severe vasoconstriction and therefore tubular dysfunction
- dose dependent, so lab monitoring is important
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Dark urine without RBCs signifies what?
Myoglobinuria due to rhabdo
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What can cause myoglobinuria?
- Rhabdo
- Chronic EtOH
- Seizures
- Prolonged dehydration
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What are s/sx of ATN?
- Azptemia
- N/V/malaise
- AMS
- HTN
- pericardial effusions
- arrhythmias (from hyperkalemia)
- Nonspecific diffuse abdominal pain
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What do labs show?
- Hyperkalemia
- Hyperphosphatemia
- BUN:Cr <20:1
- Decreased urine volume
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What does a UA show?
Brown, granular casts with renal tubular epithelial cells
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How do you tx?
- Nephrology referral always
- Furosemide (to address hyperkalemia, but can worse prognosis)
- Chlorothiazide IV 250-500 mg q8-12h
- Calcium supplementation
- Aluminum hydroxide
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When do you put an ATN pt on dialysis?
- Life-threatening hyperkalemia
- Worsening acidosis
- No reponse to diuretics
- complications of uremia (encephalopathy, pericarditis, seizures)
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What gives a worse prognosis?
- Oliguric maintenance phase
- Older age, severe underlying dz, multiorgan involvement
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