acute kidney injury Flashcards
AKI definition
a sudden decline in renal function over hours to days
non-oliguric
urine output is >400c/day
oliguric
urine output is <400 cc/day
anuric
urine output is <100cc/day
which group tends to have the highest rate of AKI
pts in the ICU, 50% have AKI
what does RIFLE stand for
risk, injury, failure, loss, end-stage kidney disease
what is RIFLE?
a classification system for AKI based on GFR and urine output
what is AKIN?
AKI network
classification for AKI based on Scr and urine output
What is KDIGO used for?
it is a staging system that is based on Scr and urine output
stages correlate with the risk of death and long-term outcomes
AKI stage 1 KDIGO
increase in SCr > 0.3 in 48 hrs OR
increase in SCr >1.5x baseline OR
urine volume < 0.5 ml/kg/hr x 6 hrs
3 main types of AKI
pre-renal
post renal
intrinsic renal
pre-renal AKI
any condition that leads to decreased renal perfusion
60% of cases of AKI
pre-renal AKI pathophys
decreased perfusion activates RAAS.
release of renin then releases ADH= vessel contraction to preserve blood flow to heart and brain
=decreased GFR so kidneys respond by concentrating urine and holding onto Na to try and reabsorb water
causes of pre-renal AKI
decreased volume (GI losses, hypovolemia)
decreased effective volume (cirrhosis, CHF)
Rx (ACE/ARBs, NSAIDs)
cardiorenal syndrome
cause of pre-renal AKI that results from decreased cardiac performance leading to decreased cardiac output which leads to decreased renal perfusion and increased water and Na retention (hypervolemia)
hepatorenal syndrome
consequence of cirrhosis that causes pre-renal AKI due to decreased renal blood flow
most likely due to portal hypertension leading to decreased GFR
clinical presentation of pre-renal AKI
signs of volume depletion
orthostatic hypotension
reduced skin turgor, dry mucous membranes
ascites, edema
(history is essential for revealing cause)
pre-renal AKI diagnostic findings
FeNA <1%
BUN:Cr ratio > 20:1
urine Na <20
how do you determine the mechanism of AKI?
clinical presentation, history, response to therapy
pre-renal AKI treatment
supportive care
fluid repletion with normal saline or LR
treat underlying cause (blood transfusions, hold rx that can contribute)
you would give ____ for hypovolemia and ___ for hypervolemia
IV fluids
diuretics
what is FeNA?
fractional excretion of Na, used to distinguish pre-renal AKI from ATN
FeNA<1= pre-renal AKI
FeNA > 2= acute tubular necrosis
*may not be accurate
pre-renal AKI response to treatment
rapid improvement in renal function following acute intervention
intrinsic AKI
AKI that leads to severe direct kidney damage
~35% of cases of AKI
types of intrinsic renal injury
tubular
interstitial
glomerular
vascular
acute tubular injury
causes 85% of intrinsic AKIs
can be ischemic or nephrotoxic (from drugs)
ischemic ATI pathophys
severe decrease in renal blood flow leads to tubular cell injury and inflammation secondarily, which ultimately results in necrosis of cells and impaired reabsorption
toxic ATI pathophys
injury occurs to tubular cells directly due to nephrotoxic substances leading to decreased GFR
ATI diagnosis
history: is there event that may have caused it?
FeNa>2, progressive rise in Cr
urinalysis shows muddy brown granular epithelial casts
lack of improvement in Cr with IV fluids
what is a difference between ATI and prerenal AKI based on Cr?
prerenal AKI BUN:Cr = >20:1
ATI= <15:1
there is a lack of improvement in Cr with IV fluids in ATI, prerenal Cr improves with repletion
ATI treatment
supportive care
remove nephrotoxic offending agents
carefully balance fluid and electrolytes without overloading (depends on urine output)
acute glomerulonephritis
intrinsic cause of AKI that is the inflammation and damage of the glomeruli
acute GN diagnosis
urinalysis with protein, blood, WBC, RBC cases
evidence of other systemic disease
**renal biopsy to find out cause
acute interstitial damage
acute inflammation of renal tubules and interstitial that can cause intrinsic AKI
acute interstitial damage pathophysiology
hypersensitivity reaction usually to drugs or infection that causes inflammation and damage to the interstitial fluid
drugs that can cause acute interstitial damage
abx PPIs cephalosporins sulfonamides penicillin NSAIDs
acute interstitial damage physical exam
rash, fever, CVA tenderness
acute interstitial damage diagnosis
urinalysis with WBC casts
PBS shows eosinophilia
renal biopsy shows interstitial T-cell and monocyte infiltration
acute interstitial damage treatment
stop the offending rx that is causing reaction (no shit)
steroids, IV fluids
what can vascular injury cause and how?
can cause intrinsic AKI due to injury to the infrarenal vessels
main types of rx that can lead to nephrotoxicity
antibiotics, acyclovir, amphotericin b, MTX, cisplatin, NSAIDs, cyclosporine, iodine and gadolinium contrast
causes of vascular injury
HUS, TTP, malignant HTN, vasculitis, atheroembolic disease
physical exam findings of vascular injury
petechiae, purpura, livedo reticularis, thromboemboli
vascular injury diagnosis and treatment
renal US
treatment to get rid of clot-angioplasty, endovascular tx, thrombolytics
post-renal AKI pathophys
acute bilateral urinary flow obstruction leads to increase in intratubular pressure and causes decrease in GFR, can also lead to impaired renal blood flow
causes of post-renal AKI
BPH, stones, tumors, neurogenic bladder, iatrogenic like from catheter injury
anything that causes bilateral obstruction of urinary flow
post renal AKI clinical presentation
- decreased or no urine output
- infection or UTI due to obstruction
- flank pain if due to stones
post-renal AKI diagnosis
renal US or CT scan of abdomen/pelvis showing bladder distention, high postpaid residual volume, stones
post-renal AKI tx
relieve obstruction
- stents for stones
- catheterization
- rx for BPH
one word for the cause of pre-renal AKI
hypoperfusion
two words for the cause of intrinsic AKI
parenchymal damage
one word for the cause of post-renal AKI
obstruction
hemodynamic support for AKI pt who is hypovolemic
IV fluid resuscitation
consider pressors if pt is very hypotensive
hemodynamic support for AKI pt who is hypervolemic
fluid restriction
consider loop diuretics if pt is volume overloaded
hemodynamic support for AKI pt who is euvolemic or unknown volume status
try administering a small amount of IV fluid and seeing if pt is responsive
most widely used classification system for AKI
KDIGO- based on SCr and urine output