AKI- MJ Flashcards
What is the definition of AKI?
>50% decrease in GFR over a period of hours to days, with any accompanying accumulation of nitrogenous wastes in the body and inability to maintain fluid and electrolyte balance
(all occuring over less than 3 months)
What is the KDIGO classification of AKI? (3)
Increase in creatinine by > 0.3 w/in 48hrs
OR
Increase in creatinine >1.5x baseline, which occured w/in the last 7 days
OR
Urine volume < 0.5mL for 6 hrs
According to KDIGO, what is the creatinine and urine output criteria for stage 1 AKI?
(note: creatinine criteria is more important than urine output)
Creatinine criteria: Cr 1.5-1.9x baseline OR Cr increase >0.3
Urine output criteria: <0.5mL x6-12 hrs

According to KDIGO, what is the creatinine and urine output criteria for stage 2 AKI?
(note: creatinine criteria is more important than urine output)
Creatinine criteria: Cr 2-2.9x baseline
Urine output criteria: <0.5ml x >12 hours

According to KDIGO, what is the creatinine and urine output criteria for stage 3 AKI?
(note: creatinine criteria is more important than urine output)
Creatinine Criteria:
- Cr >3x baseline OR
- Cr >4mg/dL OR
- Initiation of dialysis
Urine output Criteria:
- <0.3ml x >24hrs OR
- anuria x >12hrs

What is the main difference between the AKIN (Acute Kidney Injury Network) from the KDIGO classifications for staging of AKI?
The main difference is in stage 3 where AKIN also includes the following serum criteria:
Increases in Cr to >3x baseline (or Cr >4mg/dl) w/ an acute increase of at least 0.5mg/dl

What is the RIFLE (Acute Dialysis Quality Initiative) classification for AKI?
(old, not preferred method)
- Risk- Cr 1.5 x normal
- Injury- Cr 2 x normal
- Failure- Cr 3 x normal (acute rise > 0.5mg/dl)
- Loss- Loss of function for > 4 weeks
- End- ESRD- Complete loss of function > 12 weeks

If a patient is admitted to the ICU due to AKI, what is the mortality rate of this group?
Of those that survive, 30% remain on what?
- In hospital mortality= 40-65%
- Those who survive, 30% remain on long term dialysis
How much urine produced in 24hrs is considered nonoliguia? Oliguria? Anuria?
How do you monitor urine output in real time?
Nonoliguria= >500ml
Oliguria= <500ml
Anuria= <100ml
Monitor using a foley catheter
Is prerenal, intrinsic or postrenal AKI most common?
Prerenal (60-70%)
What labs and diagnostic studies should be ordered for evaluation of AKI?
•Labs
- Urine studies (UA, urine Na, urine osmolality)
- CBC, serum electrolytes
•Diagnostics
- Ultrasound or possibly CT
- EKG
What is the first line diagnostic tool for evaluating the kidney?
ultrasound
Is the normal range of serum creatinine higher in a male or female?
Greater than 4mg/dl indicates what?
- Higher in males (b/c of muscle mass)
- Greater than 4mg/dL= serious renal impairment
What is the relationship between creatinine levels and GFR?
(as GFR decreases, what happens to Cr?)
Inverse relationship: As GFR decreases, creatinine increases
(If GFR is 1/2 normal, Cr will be 2x normal)

What is the BUN/Creat ratio for prerenal AKI? What is the Fractional excretion NA (FENa)?
BUN/Creat ratio= >20:1
FENA= <1%

What is the BUN/Creat ratio for intrarenal AKI? What is the Fractional excretion NA (FENa)?
BUN/Creat ratio= <20:1
FENA= >3%

What is the BUN/Creat ratio for postrenal AKI? What is seen on UA?
BUN/Creat= <20:1
UA= Hyaline casts

What is seen on UA for intrinsic AKI?
Dark Granular casts
What is the most sensitive way to differntiate prerenal vs acute tubular necrosis (intrinsic)?
Fractional Excretion of Sodium (FENa)

What is the FENa in prerenal vs intrinsic AKI?
prerenal= <1%
intrinsic= >3%
if 1-3%= either or both
T/F: Do low or high fluid statuses cause prerenal AKI?
True
Ex of low: anemia, hemorrhage, dehydration
Ex of high: Cardiovascular states (did not focus on this)
Prerenal Azotemia is characterized by what?
Inadequate blood perfusion to the kidneys
What are the 3 main overarching etiologies of prerenal azotemia?
- Vascular Depletion
- Low Cardiac Output
- Change in vascular resistance
Prerenal Azotemia etiologies:
Vascular depletion–> hypovolemia from what?
- Renal loss
- Addisons, DKA, etc
- Extrarenal loss
- Vomiting, diarrhea, pancreatitis, burns, sweating, etc
A cause of prerenal azotemia is low cardiac output. What are the 6 possible causes of this and of those, which is the most common?
- CHF (MC)
- Pulmonary embolism
- Cardiac Tamponade
- Positive pressure ventilation
- Arrhythmia
- Cardiogenic shock
A cause of prerenal azotemia is vascular resistance caused by what 3 things? (in general)
- Systemically (sepsis, anaphylaxis, anesthesia)
- Medications (ACE, NSAIDs, Vasopressors)
- Renal artery stenosis (increased resistance and decreased perfusion)
What 7 meds can cause vascular resistance resulting in Prerenal Azotemia?
1. ACE-inhibitors
2. NSAIDs
- Epinephrine
- norepinephrine
- high dose dopamine
- anesthetic agents
- cyclosporine
What are the 9 signs and symptoms of prerenal azotemia?
- Low urine output
- Dry mouth
- Hypotension
- Tachycardia
- Thirst
- Weight loss (weight gain in CHF)
- Decreased skin turgor
- Edema (in CHF)
- Also symptoms related to heart/liver disease/sepsis
Do the following diagnostic studies indicate prerenal azotemia, intrinsic renal disease or postrenal azotemia as the cause of AKI?
- BUN/creatinine ratio: > 20:1
- Urine sodium: < 20 mEq/dL
- FENa: < 1%
Prerenal azotemia
What is the treatment for prerenal azotemia if the cause is a volume depletion?
Fluid Resuscitation
What is the treatment for prerenal azotemia if the cause is a volume overload? (3 things)
- Diuresis
- Inotropes
- Fluid restriction
What is the treatment for prerenal azotemia if the cause is a vascular resistance? (2 things)
- Treat cause
- Inotropes
What are the 4 causes of intrinsic renal disease (a cause of AKI) and which one is most common?
- Tubular disease- Acute Tubular Necrosis (MC- 85%)
- Glomerular Disease
- Vascular Disease (ex: clots in the kidney)
- Intersitial disease
Intrinsic Renal Disease causing AKI:
What are the 2 most common causes of Acute Tubular Necrosis?
- Ischemic
- Toxin Exposure
Ischemic causes of acute tubular necrosis are usually preceded by what?
Prerenal azotemia
- Prolonged low perfusion states (dehydration, sepsis)
- decreased GFR and parenchymal cellular perfusion
AKI: Intrinsic Renal Disease
What are the 5 exogenous nephrotoxins that can cause Acute Tubular Necrosis?
- Vancomycin
- Aminoglycosides
- Amphotericin B
- Antineoplastics (Cyclosporine)
- Contrast Nephropathy
AKI: Intrinsic renal disease is characterized by what?
Damage or injury within renal parenchyma making it unable to keep its gradients
- Necrosis
- Apoptosis
- Inflammatory response (Nephritic syndromes)
AKI: Intrinsic Renal Disease–> Exogenous nephrotoxins causing ATN
The level of nephrotoxicity of Vancomycin increases when combined with which medication?
Pipercillin-tazobactam
AKI: Intrinsic Renal Disease–> Exogenous nephrotoxins causing ATN
Amphotericin B can cause severe _______ and ______
vasoconstricion and tissue damage
AKI: Intrinsic Renal Disease–> Exogenous nephrotoxins causing ATN
- Contrast nephropathy is the ____ leading cause of renal failure in hospitalized patients
- This is caused by what 2 things?
- Contrast nephropathy is the 2nd leading cause of renal failure in hospitalized patients
- Caused from renal tubular epithelial cell toxicity and renal medullary ischemia
AKI: Intrinsic Renal Disease–> Exogenous nephrotoxins causing ATN
- Contrast nephropathy usually occurs within how many hours after exposure?
24-48 hours
AKI: Intrinsic Renal Disease–> Exogenous nephrotoxins causing ATN
- What are the 7 predisposing factors of Contrast Nephropathy?
- Diabetes (10-50%)
- Age
- Preexisting renal disease
- Volume depletion
- CHF
- Repeated doses of contrast
- ACE-I and NSAID use
(“PAD CAR V”)
AKI: Intrinsic Renal Disease–> Exogenous nephrotoxins causing ATN
- How do you prevent Contrast Nephropathy?
1. Hydration is key! (better than any other tx)
- Acetylcysteinie
- Sodium Bicarbonate
AKI: Intrinsic Renal Disease
- What are the 4 endogenous nephrotoxins that can cause Acute Tubular Necrosis?
- Heme containing products (Hemolytic anemia)
- Uric acid (Chemo MCC, Tumor lysis syndrome)
- Paraprotiens (Bence Jones proteins in multiple myeloma)
- Rhabdomyolysis
The following describes which cause of intrinsic renal disease?
- 10-15% of cases of intrinsic renal failure
- Characterized by edema and tubular damage from interstitial inflammation (cell mediated immune rxn)
- Drugs- MC cause
- Can also be Infectious (CMV, Strep)
Interstitial Nephritis
What 3 drugs are the most common cause of interstitial nephritis (a cause of Intrinsic Renal Disease)
- PCN
- Sulfa
- NSAIDs
What are the 5 signs/symptoms of intrinsic renal disease caused by interstitial nephritis?
•Fever (>80%)
•Rash (20-50%)
- Arthralgias
- Plasma eosinophilia
- RBC, WBC and white cell casts in UA
What is the course of Interstitial Nephritis (a cause of intrinsic renal disease)?
- Usually self-limiting
- Recovery _____ to ______
- Rarely progress to ESRD
•Recovery weeks to months
What 2 things may be needed in the short term to treat Interstitial Nephritis (a cause of intrinsic renal disease)?
- Dialysis may be needed in the short term
- Steroids may be given- short term, high dose
What is the hallmark of intrinsic renal disease (a cause of AKI)
Unable to concentrate urine
(will be on exam)
The following are diagnostic findings of which cause of AKI? (prerenal, intrinsic or postrenal)
•Urine:
- Dark granular casts
- Urine sodium: > 30 mEq/dL
- ABG: metabolic acidosis
- Serum:
- • FENa: > 2-3%
- •BUN/creatinine ratio: < 20:1
Intrinsic Renal Disease
The following are causes of what?(prerenal, intrinsic or postrenal)
•OBSTRUCTION!!!
•Nephrolithiasis
•Bladder stones
•BPH
- Malignancy
- Medications that cause urinary retention
- Poorly emptied neurogenic bladder
Postrenal azotemia (cause of AKI)
What are the 8 complications of AKI?
- Volume regulation
- Metabolic Acidosis
- Hyperkalemia
- Hyperphosphatemia
- Excertory failure
- Metabolic failure
- Hypocalcemia and hypermagnesemia
What is the course of AKI? (3 phases, how long does each phase last?)
- Initiation
- Maintenance phase–> days to weeks
- Recovery (diuresis) phase–> weeks to months
What are the 4 causes of death in a person with AKI? What is the most common cause?
•Infections (30-70%)
- Cardiovascular events (5-30%)
- GI, pulmonary or neurologic complications (7-30%)
- Hyperkalemia or dialysis related (1-2%)
The following describes which complication of AKI?
- Na and water retention leads to HTN and edema
- Hyponatremia
Volume regulation
The following describes which complication of AKI?
- Tubules fail to regenerate bicarbonate and secrete H+ ions into urine
- Retention of phosphate causing a wide anion gap
Metabolic Acidosis
The following describes which complication of AKI?
•Limited potassium secretion and shift out of cells in exchange for H+ ions which accumulates in renal acidosis
Hyperkalemia
A complication of AKI is hyperphosphatemia. What is this due to?
–Due to filtration failure–> leads to hypocalcemia–> PTH release
The following describes which complication of AKI?
- Erythropoietin production falls–> bone marrow is depressed leading to anemia
- Malabsorption of dietary calcium
- Renin is overproduced causing HTN
Metabolic Failure