Intrinsic Acute Kidney Injury Flashcards
What is creatinine and how is it used?
a molecule released at a steady state from muscle, filtered by kidney
instead state, allows tracking of kidney function in individual
needs to be converted to GFR via formula
if there is a rise of 0.3 mg/dL, signifies AKI
stages of chronic kidney disease
stage 1 - GFR >= 90 mL/min, proteinuria
stage 2 - GFR between 60 and 89 mL/min
stage 3 - GFR between 30 and 59 mL/min
stage 4 - GFR between 15 and 29 mL/min
stage 5 - GFR less than 15 mL/min
definition of acute renal failure
an abrupt (within 48 hours) reduction in kidney function
absolute increase in serum creatining of either >= 0.3 mg/dL or a percentage increase of >= 50%
a reduction in UOP (documented oliguria of < 0.5 mL/kg per h for > 6 hours
AKIN creatinine criteria for acute kidney injury
stage 1 - increase in SCr of 1.5-2 or >= 0.3 mg/dL
stage 2 - increase in serum creatinine of 2-3 fold
stage 3 - increase in Scr > 3 fold or baseline Cr. > 4 with an acute rise > 0.5 mg/dL
AKIN urin output criteria for acute kidney injury
stage 1 - < 0.5 mL/kg per h for 6 h
stage 2 - < 0.5 mL/kg per h for 12 h
stage 3 - < 0.3 mL/kg per h for 24h, or anuria for 12 h
obstructive uropathy
acute renal failure occurring with obstruction of both urinary outflow tracts or the outflow tract of a single kidney
etiologies include - prostatic or cervical neoplasia, neurogenic bladder, intraluminal obstruction (crystals, stones blood)
clinical findings of obstructive uropathy
may or may not be oliguric
hyperkalemia
treatment of obstructive uropathy
relief of obstruction
recovery of renal function may be inversely related to length of time obstruction persists
recognize the possibility of a diuretic phase
urinary indices for prerenal injury
UOsm > 500
UNa < 20
FENa < 1
urinary indices for ATN
UOsm < 350
UNa > 40
FENa > 1
urinary indices for AGN
UOsm 300-500+
UNa < 40
FENa < 1
urinary indices for obstructive uropathy
UOsm 300-500
UNa > 40
FENa > 1
What is the most common cause of ischemic acute renal failure?
severe and sustained prerenal azotemia
Describe the current state of predictive tests for extent of renal injury.
creatinine is not sensitive for renal injury
no biomarkers like cardiology yet
urine sediment is helpful but takes skill
normotensive ischemic AKI
normally the kidney maintains blood flow through a wide range of pressures
however in patients with imparied autoregulation, the GFR falls below normal values while the mean arterial pressure remains within the normal range
What causes dilation of the afferent artery and what does that do?
prostaglandings
increases GCP and nephron plasma flow, and GFR
What causes afferent artery constriction aand what does that do?
NSAIDs
decreased glomerular capillary pressure
decreased nephron plasma flow and GFR
What causes efferent arteriole dilation and what does that do?
ACE inhibitors and ARBs
decreases GCP
increases nephron plasma flow
decreases GFR
What causes efferent arteriole constriction, and what does this do?
increased glomerular capillary pressure
decrease nephron plasma flow, but increases GFR
risk factors for contrast nephropathy
pre-existing CKD (particularly GFR < 60
diabetes mellitus
heart disease
hypotension
age
dehydration
mechanism of radiocontrast nephropatyh
direct tubular toxicity
inducing vasospasm and ischemia
treatment for radiocontrast nephropathy
defined by an increase in creatinine of 0.5 mg/dL or an increase in creatinine of 25% from baseline
prevention is the best medicine
time for kidneys to heal
rhabdomyolysis (pigment nephropathy)
muscle damage (release of myoglobin) or hemolysis (releas of hemoglobin) can directly damage the kidney
What is commonly seen in urinalysis for ATN?
dark, granular casts (brown casts)
treatment of pigment nephropathy
stop the underlying medical issue
IVF to prevent kidney damage
thrombotic microangiopathy
occlusion of small blood vessels that occurs in thrombotic microangiopathies can cause an intrinsic ischemia in the kidney and AKI
urine sediment may be bland, pigmented (ATN) casts can be found along with blood or urine
treatment of thrombotic microangiopathy
stop causative medicine if one is bieng used
treat specific etiology if one is identified
plasmapharesis is usually recommended as early as possible in adults
