Acute Kidney Injury Flashcards
What is the clinical criteria for Risk?
Increase in serum creatinine to 1.5-2 from baseline
Uop less than 0.5 ml/kg/hr for 6 hours
What is the clinical criteria for injury?
Increase in serum creatinine to 2-3 x baseline
UOP less than 0.5 ml/kg/hr for 12 hours
What is the clinical criteria for failure?
Increase in serum creatinine greater than 3 X baseline
UOP less than 0.3ml/kg/hr for 24 hours
Anuria for 12 hours
What is the criteria for Loss?
Loss of kidney function for more than 4 weeks
What is the criteria for ESRD?
Loss of kidney function for more than 3 months
What is the AKIN criteria?
Diagnostic scale for AKI that came out after RIFLE
What is AKIN stage 1 criteria
Increase in serum creatinine of greater than 0.3 mg/dl or 1.5-2 X baseline
UOP less tha 0.5 ml/kg/hr for greater than 8 hours
What is AKIN stage 2 criteria?
Increase in serum creatinine to greater than 2-3 X baseline
UOP less tha 0.5 ml/kg/hr for over 12 hours
What is the AKIN stage 3 criteria?
Increase in serum creatinine to 3 X baseline
Increase in serum creatinine greater than 4 mg/dl with an acute increase of greater than 0.5 mg/dl
UOP less than 0.5 ml/kg/hr for 24 hours
Anuria for 12 hours
What is the insult in pre renal disorders?
A decrease in renal blood flow
Usually from heart failure, hypovolemia, shock
What causes ATN?
Septic shock
Contrast dye
Nephrotoxic drugs
Rhabdo
What is the pathological process in ATN?
Oxidative injury causes the epithelial lining of the renal tubule to die. They slough into the lumen and create obstruction and back pressure, thereby lowering the GFR via the tubuloglomelular feed back system
What is the most common cause of AKI?
ATN
What is the most cause of AKI.
Sepsis
What does a spot urine sodium less than 20 mean?
The process is pre renal
What does a spot urine of greater than 40 mean?
This process is intrinsic
What are the exceptions to the spot urine sodium of over 40?
It can be prerenal if you have ongoing dieresis, or if they have CKD
What does it mean if the FeNa is less than 1%?
Prerenal
What does it mean if FeUrea is greater than 50%?
It is intrinsic
What are the exception to FeNa.
Diuretics
CKD
Can be false low in ARF with sepsis, contrast, rhabdo
What is the advantage of using FeUrea?
It is not influenced by diuretics
How long do you continue a fluid challenge?
Until you get response or are worried about volume overload
What is the rifle criteria?
Risk Injury Failure Loss Esrd
What is the mechanism of AKI with contrast?
Direct renal tubule injury
Renal vasoconstriction
Generation of toxic oxygen metabolites
When does AKI from contrast usually appear?
Within 72 hours
How long does it take contrast nephropathy to resolve?
2 weeks
What is the most effective preventive measure against contrast nephropathy?
IV hydration : isotonic Aline 100-150 ml/hr started 3-12 hours before the procedure and continued 6-24 hours after
How much fluid should you give if you must do a scan emergently in a patient at high risk for AKI?
300-500 ml
What is the high dose NAC regimen for contrast nephropathy?
1,200 mg pro bid X 48 hours beginning the night before the procedure
What is the NAC dosing for an emergency procedure?
1,200 mg prior
What are the most common drugs to cause AIN?
Penicillins
What are the signs of AIN?
Fever, rash, eosinophilia, sterile pyuria
How do hemoglobin and myoglobin cause ATN?
The iron moiety makes free radicals
What is the treatment of ATN.
Aggressive volume
Alkaline the urine
What is the normal intra abdominal pressure?
5-7mm hg
What is IAH (intra abdominal hypertension) defined as?
Sustained increase above 12 mm hg
What is abdominal compartment syndrome defined as?
When IAP is above 20 mm hg and there is evidence of end organ damage
What is the equation for abdominal perfusion pressure?
MAP-IAP
What is the goal APP for renal perfusion to happen?
APP greater than 60
What is renal perfusion pressure equivalent to in IAH?
The APP
Why does IAP have made greater impact on GFR than an equivalent decrease in MAP?
Because it is the equivalent of proximal tubule pressure and because
FG= MAP- IAP x2
How should you try to reduce IAP?
Sedation to reduce abdominal muscle contraction
Avoiding elevating the head of the bed more than 20 degrees
Avoiding positive fluid balance
How can you measure IAP.
Through a decompressed bladder by injecting 25-50 ml of saline thru a special catheter
What are the indication for RRT?
Volume overload
Life threatening hyperkalemia or metabolic acidosis
Removal of toxins
How does hemodialysis work?
By diffusion which is driven by concentration gradient
What is the counter current exchange?
Blood and dialysis fluid are run in opposite directions to maintain the concentration gradient
What is the benefit of dialysis?
Rapid clearance of small solutes
What is the disadvantage of dialysis?
Limited removal of large molecules
The need to maintain blood flow at 200-300ml/min which creates risk of hypotension
How does hemo filtration work?
Removes solutes by convection, where a hydrostatic pressure gradient is used to move a solute containing fluid across a semipermeable membrane (solvent drag method)
What are the advantages of hemo Filtration?
Gradual removals of fluid without hemodynamics compromise
Large amount of fluid removal
Removes larger molecules (better for removing toxins)
What are the disadvantages of hemofiltration?
Slow
Continuous
need IV fluid replacement for filtration loss since it is basically washed away with water