Acute Renal Failure Flashcards
(50 cards)
Define azotemia
Excess of urea or other nitrogenous compounds in blood (aka high BUN)
MC causes of AKI
- Prerenal (RBF, 40-80% of cases)
- Intrinsic renal (small vessels, glomeruli, tubules)
- Postrenal (obstruction to urine flow in ureters, bladder, urethra)
Pathophys of AKI
- Low RBF leads to ischemia and cell death
- Continued cell injury even after restoration of RBF
- GFR is decreased and infiltrates leak
- Dying cells slough off which obstruct tubules
Recovery from AKI is dependent upon what?
Restoration of normal RBF
Clinical presentation of prerenal failure
- Hypovolemia
- Elders w/vague mental status
- CHF w/low renal perfusion
- Restricted fluid access
Clinical presentation of intrinsic renal failure
- Nephritic syndrome
- Acute tubular necrosis
- Pigment induced AKI
- Allergic interstitial nephritis
Nephritic diseases are characterized by:
Active urine sediment w/glomerular hematuria (and often with proteinuria)
Clinical presentation of postrenal failure
- Older men w/prostatic obstruction
- Gyn surgery or abd/pelvic malignancy
- Flank pain and hematuria
What is the most important thing to assess in clinical presentation of AKI?
Volume status!
Relationship of urine output and AKI?
- Most causes of AKI are nonoliguric
- Normal urine output
Interpretation of urine electrolytes
May be erroneous in nonoliguric states (normal urine output)
What is FENa?
- Marker of Na excretion in kidneys
- Useful only in oliguria (to determine whether prerenal or intrinisic failure)
- Less than 1% is prerenal
- Greater than 1% is ATN
How is GFR measured for kidney function?
- Not possible to measure directly
- Serum Cr is used as a surrogate to calculate (estimate) GFR
Treatment of AKI
-Correct volume and electrolytes
-Avoid nephrotoxic agents, adjust doses of renal excreted meds
-Salt and fluid restriction
(mainly supportive tx)
What are the RIFLE criteria?
- Uniform, accepted definition of AKI
- Risk, Injury, Failure, Loss, ESRD
Iatrogenic renal injury occurs MC when?
When RBF is low
What happens once RBF is restored?
- Remaining functional nephrons increase their filtration leading to hypertrophy
- Continued hyperfiltration results in progressive glomerular sclerosis
How does urine output correlate with GFR?
Urine output does NOT correlate well with changes in GFR
How does urine output present in most cases of AKI?
50-60% of all causes of AKI are nonoliguric (urine output does not change)
If serum Cr is greater than or equal to 1.5 mg/dL/day, what must be ruled out?
Rhabdomyolysis
What is a quick way to determine furosemide dose?
Age + BUN
How does AKI MC present in children?
Prerenal - hypovolemia due to gastroenteritis (profuse vomiting)
What should be suspected when bladder pressure is over 25 mm Hg?
Suspect AKI as a result of abdominal compartment syndrome
What is the hallmark of intrinsic failure?
Structural injury in the kidney (either ischemic or cytotoxic)
