Exam 3 - Acute Kidney Injury Flashcards
What is the general criteria for diagnosis of AKI based on?
Usually based on serum creatinine levels OR decrease in a patient’s urine output
What is the KDIGO Diagnostic criteria for AKI?
- Increase in serum creatinine by > or equal to 0.3 mL/dL within 48 hours
OR - Increase in serum creatinine > or equal to 1.5 times baseline
OR - Urine volume < 0.5 mL/kg/hour for six hours
What is the KDIGO staging and associated Cr levels?
Stage 1: Increase in serum Cr to 1.5-1.9 times baseline
Stage 2: Increase in serum Cr to 2.0-2.9 times baseline
Stage 3: Increase in serum Cr to 3.0 times baseline OR anuria for > 12 hours OR initiation of renal replacement therapy
What are the classifications of AKI etiology?
- Prerenal: decreased renal perfusion
- Intrinsic renal: pathology of the vessels, glomeruli, or tubules
- Postrenal: obstructive
What is AKI in the hospital most often from?
- Prerenal
- Intrinsic
What is the most common AKI etiology?
ATN (intrinsic)
What are major causes of prerenal disease?
- True volume depletion
- Hypotension
- Edematous states
- Selective renal ischemia
- Drugs affecting GFR
What are major causes of intrinsic renal disease?
- Renal ischemia
- Sepsis
- Nephrotoxins (IV contrast)
How is ATN caused by IV contrast?
IV contrast causes renal tubular epithelial cell toxicity and renal medullary ischemia from vasoconstriction
What are risk factors for developing ATN from IV contrast?
- Preexisting renal disease
- Volume depletion
- Repeated doses of contrast
How can you avoid ATN caused by IV contrast?
- Hydration
- Use of low-osmolal agents at low doses
- Avoid repetitive doses
- Avoidance of nephrotoxic drugs for at least 48 hours after exposure (Metformin, NSAIDs)
A reduction in GFR in patients without intrinsic renal disease requires what type of obstruction?
Requires bilateral obstruction, or unilateral obstruction if single functioning kidney
What urine output levels differentiate oliguric from anuric?
Oliguric: < 400 mL/24 hours
Anuric: < 50 to 100 mL/24 hours
Muddy brown casts on UA are pathognomonic for what?
ATN (intrinsic)
What equation/calculation can help distinguish prerenal AKI from intrinsic ATN?
FENa (fractional excretion of sodium)
If the FENa is <1%, what does this suggest?
If the FENa is >2%, what does this suggest?
<1% suggests prerenal
> 2% suggests intrinsic (ATN)
- **between 1-2% can be seen with either disorder
- **unreliable in patients taking diuretics
What are some pearls/pitfalls to note with using FENa as a tool?
- Unreliable for patients on diuretics
- Serum creatine is not stable in AKI
When is renal imaging typically performed and what is a major reason for doing it?
Generally performed in patients with AKI when the underlying cause is not immediately apparent
Major reason is to assess for urinary tract obstruction
What is the most common radiographic technique for AKI?
Renal ultrasound
When is a renal biopsy done?
Rarely, but in those who have no clear explanation for AKI.
If creatinine is markedly elevated or if it significantly worsens over the course of days
What are some contraindications to a renal biopsy?
- Bleeding diathesis
- Severe HTN
- Pyelonephritis
- Renal tumor
- Solitary native kidney
While many patients have mild AKI, what life-threatening complications can occur?
- Volume imbalance (depletion or overload)
- Metabolic acidosis (pH < 7.4)
- Hyperkalemia (K+ > 5.5)
- Hypocalcemia
- Hyperphosphatemia
- Uremia
If patient with AKI presents with history and exam consistent with volume depletion, and/or has oliguria, what should you do?
Administer IV crystalloid isotonic fluids (0.9 NS)
Begin wtih 1-3 liters of fluid and performed repeated assessments
If patient with AKI presents with clinical signs of volume depletion and you treat with IV fluids but they do not respond, what does this suggest?
Unlikely to have prerenal disease and more likely to have ATN or other forms of instrinsic AKI
