Jan18 M1-Acute Kidney Injury Flashcards
(47 cards)
3 types of AKI
pre-renal, renal, post-renal
pre-renal AKI def
low BP, blood loss, hemodynamic prob (volume, pressure, fluid)
renal AKI def
disease of parenchyma (glomeruli, mesengium, tubules)
post-renal AKI def
obstruction (problem with urine outflow. stones, BPH, tumor)
causes of pre-renal AKI
relative drop in circulating volume (RAS, NSAIDs, CHF, cirrhosis/ascites, sepsis (vasodilation)) or effective drop in volume (GI loss, bleeding, etc.)
renal causes of AKI (5 main)
- acute GN (nephritic: APIGN, SLE, etc.)
- RPGN/crescentic
- ATN (post-infectious or toxic)
- AIN (drug-induced)
- Intratubular obstruction
post-renal causes of AKI
- prostatic disease
- pelvic or retroperitoneal malignancy
AKI definition
EITHER
1. plasma Cr +50 or + 50% or 50% drop GFR IN A MONTH
OR
2. oliguria (less 30cc/hour or less 200cc/8 hours)
anuria and oliguria def
anuria = less 50cc/day oliguria = less 500cc/day
how to calculate one’s minimal urine output
daily solute load in mosm/1200 mosmkg-1 (which is the max U conc)
ATN as cause vs as consequence of AKI
ATN can cause a renal AKI
ATN can be a consequence of a pre-renal AKI bc of ischemia and damage to the tubules
why ATN occurs
O2 level already low in medulla + high metabolism in the tubules (*PCT and TAL) so vulnerable to low flow
can ATN heal? why?
yes. tubules are epithelial cells, like skin, so they can repair
4 most common causes of AKI in the hospital
ATN, pre-renal, acute on chronic (already vulnerable bc low GFR), obstruction (urinary tract)
how to dx ATN vs pre-renal cause of AKI (clinically with no labs)
pre-renal: Cr and UO improved with fluid
ATN: takes days to months to repair (tubular damage)
labs to differentiate ATN vs pre-renal
ATN: urine sediment has muddy brown casts (dead tubular cells)
pre-renal: no muddy brown casts
can you get pre-renal failure from RAS alone?
no. need to add a clear cut time where the BP drop or gave ACEi
ATN vs pre-renal AKI: how U lytes can help** (must remember!!)**
pre-renal: U Na less 25 mM
ATN: U Na more 40 mM
best test to diff pre-renal vs ATN
FENa (fractional excretion of Na)
FENa value for pre-renal vs ATN AKI
less 1% = pre-renal
1-2% = can be any
more 2% = ATN
FENa formula
(UNa x PCr)/(PNa x UCr) x 100
other tests to check pre-renal vs ATN
serum urea to Cr: above 20 favors ATN (no urea reabso)
U osms: above 500 favors pre-renal (bc holding on to water)
gravity: more 1.020 is pre-renal (bc holding on to wateR)
treatment + what if no improvement in ATN
NS until euvolemia (check ctly volume status
Cr still rising in CHF + worsening = dialysis
how to control BP in unilateral vs bilateral RAS
unilateral: give ACEi (one kidney drops GFR, other increases)
bilateral: can’t give ACEi bc both kidneys drop their GFR
