Acute Kidney Injury (AKI)

Question 1

Define: Acute Kidney Injury

Answer 1

acute worsening in renal function

Question 2

Define: Oliguria

Answer 2

urine output (UOP) < 500 mL/day

Question 3

Define: Anuria

Answer 3

urine output (UOP) < 50 mL/day

Question 4

What are the risk factors of AKI?

Answer 4

-sepsis/critical illness
-dehydration
-burns
-trauma
-surgery
-nephrotoxic drugs
-contrast agents
-advanced age
-female gender
-CKD
-diabetes
-cancer

Question 5

KDIGO AKI DEFINITION

Answer 5

increase in serum creatine (SCr) by 0.3 mg/dL within 48h OR increase in SCr to > 1.5 times baseline occurring within prior 7 days OR urine volume <0.5 mL/kg/h for 6+ hours

Question 6

RIFLE CRITERIA

Answer 6

-RISK= SCr increase 1.5-1.9x baseline or decrease in GFR >25% OR UOP 0.5mL/kg/h in 6 h
-INJURY= SCr increased 2-2.9x baseline or decrease in GFR >50% OR UOP <0.5mL/kg/h for 12 h
-FAILURE= SCr >3x baseline, decrease in GFR >75%, or 4 mg/dL OR UOP <0.3 mL/kg/h for 12 h or anuria for >12 h
-LOSS= persistent renal failure > 4 weeks
-END-STAGE RENAL DISEASE= persistent renal failure > 3 months

Question 7

Define: AKIN Stage 1

Answer 7

SCr increase 0.3 mg/dL or 1.5-2x baseline OR UOP <0.5mL/kg/h in 6h

Question 8

Define: AKIN Stage 2

Answer 8

SCr increase 2-3x baseline OR UOP <0.5 mL/kg/h for 12 h

Question 9

Define: AKIN Stage 3

Answer 9

SCr > 3x baseline, >4 mg/dL with acute increase of 0.5 mg/dL, or requiring dialysis OR UOP <0.3mL/kg/h x24 h or anuria for >12h

Question 10

What urine sediment would be found in pre-renal AKI?

Answer 10

hyaline cast, may also be normal

Question 11

What urine sediment would be found in intrinsic AKI?

Answer 11

granular casts, cellular debris

Question 12

What urine sediment would be found in post-renal AKI?

Answer 12

cellular debris

Question 13

How can AKI be diagnosed?

Answer 13

-fractional excretion of sodium (FENa): urinary excretion of sodium
-fractional excretion of urea (FEUrea): used on patients on diuretics
-renal ultrasound
-urinalysis
-renal biopsy

Question 14

Goals of therapy: AKI

Answer 14

-minimize ongoing insult
-reduce risk for complications
-expedite and restore baseline function

Question 15

What are the causes of Pre-Renal AKI?

Answer 15

hypoperfusion to the kidneys
-volume loss such as dehydration, bleeding, or burns
-decreased effective blood volume such as cardiac output, sepsis, or liver failure
-functional such as DRUGS= NSAIDS, ACE Inhibitors, ARBs, diuretics

Question 16

What is the treatment for Pre-Renal AKI?

Answer 16

-stop offending agents if possible
-fluid replacement (normal saline)
-hemodynamic support (improve utilization of blood volume, vasopressors)

Question 17

What are the causes of Intrinsic AKI?

Answer 17

structural injury
-tubular injury: acute tubular necrosis (ATN)
-interstitial injury: acute interstitial nephritis (AIN)
-glomerular injury
-vascular injury

Question 18

What is the most common cause of intrinsic AKI?

Answer 18

acute tubular necrosis (ATN)

Question 19

What are the causes of acute tubular necrosis (ATN)?

Answer 19

prolonged pre-renal AKI, drugs, or endogenous toxins

Question 20

What is the treatment for acute tubular necrosis (ANT)?

Answer 20

-stop offending agents
-manage electrolyte imbalances
-possibly diuretics with significant volume overload (furosemide)
-renal replacement therapy (RRT)= dialysis

Question 21

How can acute tubular necrosis (ATN) be prevented?

Answer 21

recognize high-risk patients such as recent surgery/trauma or drugs and encourage appropriate fluid intake especially with nephrotoxic medications

Question 22

How is Contrast Induced Nephropathy (CIN) AKI diagnosed?

Answer 22

SCr rise of 0.5+ or 25% increase in baseline within 48h of contrast

Question 23

What patients are high risk for contrast induced nephropathy (CIN)?

Answer 23

-pre-existing kidney diagnosis
-diabetic nephropathy
-age >70yo
-hypovolemia, hypotension
-anemia
-heart failure
-concomitant nephrotoxins
-large contrast doses, high-osmolality contrast

Question 24

How can contrast induced nephropathy(CIN) be prevented?

Answer 24

IV volume expansion, PO N-Acetylcystine (NAC) (controversial), ascorbic acid, or remove nephrotoxins and increase monitoring

Question 25

What are the causes of acute interstitial nephritis (AIN)?

Answer 25

*inflammation of interstitium around tubules* most commonly drug induced (antibiotics= beta-lactams, sulfa, COX-2, NSAIDS, loop diuretics, PPI or H2RAs (usually 2 weeks within exposure)) but other causes include infection, connective tissue disease, exogenous toxins

Question 26

What is the treatment of acute interstitial nephritis (AIN)?

Answer 26

-stop offending agent -treat underlying cause -if no significant improvement -> corticoidsteroids

Question 27

What are the causes of Post-Renal AKI?

Answer 27

*obstruction* -physical blockage -improper placement of urinary catheter -crystal formation -drugs: sulfonamides (antibiotics), antiretrovirals (HIV), methotrexate, acyclovir

Question 28

What is the treatment for Post-Renal AKI?

Answer 28

-remove/relieve obstruction -stop offending agents -aggressive hydration -potential for urine alkalinization if certain drugs are involved

Question 29

What are the indications for renal replacement therapy (RRT)?

Answer 29

*life threatening changes in fluids, electrolytes, or acid-base status* -A= acid/base -E= electrolyte abnormalities -I= intoxicants -O= volume overload -U= uremia

Question 30

What monitoring parameters should be put in place for a patient with AKI?

Answer 30

-body weight -fluid intake and output -signs and symptoms of edema or dehydration -BP -serum electrolytes -ab markers of renal function= SCr and BUN

Question 31

What are the complications of AKI?

Answer 31

-METABOLIC: electrolyte imbalances, acid/base disorders, accumulation of toxins -CARDIOVASCULAR: edema, hypertension, arrhythmias -hematologic: platelet dysfunction -development of CKD