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Definition of AKI
occurs within 48 hrs as evidenced by: an absolute inc in serum creatinine conc of >=0.3 mg/dL above baseline, or a >=50% increase in serum creatinine conc over baseline, or documented oliguria of <0.5 ml/kg/hr for more than 6 hours
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azotemia
elevation of blood urea nitrogen (BUN) and creatinine
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Uremia
clinical syndrome resulting from azotemia characterized by anorexia, nausea, vomiting, & mental status changes
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Pre-renal causes of AKI
dec IV vol, dec EABV, hemodynamic
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instrinsic causes of AKI
Tubules(ATN)-ischemic or toxic, Interstitial-allergic or infection, Glomeruli-glomerular inflammation, Vascular-inflammation, occlusion
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post renal causes of AKI
obstruction to ureters, bladder, urethra
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Acute tubular necrosis leads ( ) continuated by pre-renal
ischemic (prolonged hypotension, vasoconstriction)
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toxic causes of AKI
contrast dye, heavy metal poisoning, drugs causing tubular toxicity (Amph B, AGs, Contrast dye, etc), drugs causing crystal nephropathy (acyclovir, sulfonamides), intratubular pigments (myoglobin secondary to rhabdomyolysis, hemoglobin secondary to hemolysis)
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causes of AKI causing acute interstitial nephritis
Abx, antivirals, NSAIDs, diuretics, allopurinol
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causes of AKI causing glomerular inflammation (glomerulonephritis)
SLE, poststreptococcal glomerulonephritis, medications: NSAIDs, ampicillin, lithium
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causes of small vessel disease
polyarteritis nodosa, hemolytic uremic syndrome, malignant hypertension, scleroderma
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causes of large vessel disease
cholesterol emboli, thrombosis, endocarditis, renal artery stenosis, medications: oral concentrations, warfarin, thrombolytics
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causes of post-renal obstruction
bladder outlet (BPH), ureteral (cancer, nephrolithiasis, crystal deposition, tumor-lysis syndrome, blood clot)
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non-oliguric UOP
>500 ml/day
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oliguric UOP
50-500ml/day
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assess history for AKI
assess for disorders predisposing pt to vol depl, renal disease & obstruction, medication history history, change in voiding habits, wt gain, nephrotoxin exposure
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physical assessment
blood pressure, ECF volume status (tachycardia, orthostatic BP changes, dry mucus membranes, hypotension), physical exam, I & O's
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lab evaluation
urinalysis-examine for sediment, RBC, RBC casts, proteinuria, WBC, WBC casts, eosinophils, crystals
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BUN:creatinine ratio (-10-20:1)
- pre-renal >20:1
- instrinsic (ATN) <20:1
- post renal <20:1
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urine sodium
- pre-renal <20 mEq/L
- instrinsic (ATN) >40 mEq/L
- Post renal >40 mEq/L
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FENA%
- [urine Na * Serum Cr/Serum Na * Urine Cr]x 100
- pre-renal <!%
- instrinsic (ATN)>2%
- post-renal variable
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factors affecting reliability of FENA
diuretics, osmotic diuresis, CRF
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prevention of AKI
identify pts at risk, correct risk factors prior to therapy-esp hydration, avoid the use of potentially nephrotoxic agents in pts at risk if possible, avoid nephrotoxic combinations, adjust the dose for renal fxn prior to therapy
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monitoring diuretic therapy, goal urine output
>=ml/kg/hr, wt loss can exceed 1-2 lbs
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dopamine
0.5-2 mcg/kg/min, selectively dilates renal vasculature to incr RBF and inc UOP, increases UOP but doesn't improve creatinine clearance and no evidence that it decreases mortality, monitor UOP, BP, IV site
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Indications for dialysis (AEIOU)
- Acid-base abnormalities (acidosis pH<7.1)
- Electrolyte imbalance (hyperkalemia >6.5 mEq/L; increased Mg >2.3)
- Intoxications (Salicylates, Lithium, Methanol, Ethylene glycol, theophyllin, Pb)
- Fluid Overload (pulmonary edema)-that have not responded to interventions
- Uremia-(BUN>80-100 mg/dL, CNS complications, pericarditis, intractable N&V
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mortality causes of AKI
infection #1 cause, CV compromise, respiratory failure, GI bleed
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