Acute Kidney Injury Flashcards
What are some general indicators of renal failure?
- Impairment of GFR
- Elevation of BUN/Creatinine
general accumulation of substances typically excreted by the kidney including Drugs, K+, PO4 etc.
What defines Acute Kidney Injury?
• what labs are you looking for?
• what signs are you looking for?
Rapid Deterioration of Renal Function:
• HOURS to LESS THAN one month
Labs:
• Creatinine increase 50% over baseline value
Signs:
• Decreased urine output (NOT ALWAYS SEEN)
• Kidney becomes inable to regulate electrolytes and water
What defines oliguria?
• Anuria?
Oliguria:
Less than 400 ml urine output in 24 hours
Anuria:
Less than 100 ml urine output in 24 hours
T or F: Acute Kidney Injury is usually asymptomatic and discovered in labs.
True, we USUALLY JUST SEE THE ELEVATION in Creatinine
Are most cases of Acute Kidney Injury Reversible or Irreversible?
Most are REVERSIBLE (you can just stop giving the drug you were giving or put in a catheter etc.)
What are 5 key things you want to look for when evaluating someone who you suspect may have renal failure?
- Careful History
- Review of Hospital Chart
- Medications
- Physical Examination
- Examination of the Urine
What are you looking for on physical exam that suggests acute renal failure (ARF)?
• Look for Volume Overload or Depletion
In what type of Acute Renal Failure are Brown Granular Casts seen?
• Intrisic Renal Failure tends to produce the Brown Granular Casts
What 3 KEY URINE (not serum) values do we look at to determine if someone is in acute renal failure?
- Urine Osmolarity
- Fractional Excretion
- Urine Sediment
Postrenal Acute Renal Failure
• Key complaints
• Causes
• Diagnosis
CC:
• “I can’t pee”
Causes:
• Prostate Hypertrophy
• Pelvic or Retroperitoneal Malignancies
• Neurogenic bladder
Dx:
• ULTRASOUND is used to see Dialated (hypoechoic) calyces in the Hilum
T or F: Urinalysis is usefule in diagnosing post-renal ARF.
FALSE, Labs here don’t tell us much
What is the chain reaction that happens in response to changes that causes pre-renal failure?
Pre-renal Failure = poor perfusion of Kidney
Step 1:
• Low Effective Circulatory Volume causes…
Step 2:
• Baroreceptor Activation
Step 3:
• RAAS
• ADH (vasopressin)
• Sympathetic NS
Step 4: • Vasoconstriction • Mesangial Cell Contraction • Na+ and H2O reabsorption • Reduced Sweating • Thirst and Na+ appetite
Step 5:
• ACUTE pre-renal Failure
Are urinalysis findings useful in Acute pre-renal failure?
• if so what do you expect to see?
YES, you would expect to see Hyaline Casts
What urinary labs are useful in Acute PRE-Renal Failure?
• what does this suggest about hormone function in the kidney?
• what are you looking for?
Urine Osmolarity:
• Greater than 500 - ADH is working because you’re concentrating urine
Urinary Na:
• Less than 25 - ALDOSTERONE is working by sparing Na+
FeNa:
• Less than 1% suggests pre-renal failure
What are the 3 types of Acute Pre-renal Kidney Failure?
- Hepatorenal Syndrome
- Renal Artery Stenosis
- Drugs Preventing Autoregulation
What characterizes Hepatorenal Syndrome?
• Blood Pressure.
• Kidney Function.
• Urinalysis
- Decreased BP (systolic in 80s and 90s) in spite of Increased ECFV
- Kidneys Structurally intact but have AZOTEMIA (bun and cr. inc.) and progressive oliguria
Urinalysis:
• Normal
What is the Px. of someone with hepatorenal syndrome?
• what is the best treatment option?
Poor unless pt. receives LIVER TRANSPLANT
What 2 things must you do before giving a final Dx of Hepatorenal Sydrome?
- Rule out other Causes (this is a dx. of exclusion) - rule out nephrotoxic drugs, contrast etc.
- URINE Na+ very low (less than 10) so you need to give an INFUSION OF SIMPLE SALINE to rule out simple pre-renal condition
Explain the effect of the Folling drugs on the Afferent and Efferent Arterioles:
• NSAIDs:
• ARBs/ACE Is
NSAIDs:
• NSAIDs block PGs.
• PGs are typically used to dialate AFFERENT arteriole
• Blockage here = Decreased Blood FLow in the Kidney
ARBs/ACE Is:
• Typically the kidney Constricts the Efferent arteriole to maintain GFR
• ACE Is/ARBs block Angiotensin II from binding and affecting the efferent arteriole
•Net Effect w/ ACE = Reduced GFR
NSAID use that is concurrent with what conditions can lead to acute renal injury?
Acute Renal Injury with NSAIDS may occur in pts. with:
• True Volume Depletion
• CHF
• Cirrhosis
Cox-2 Inhibitors have similar intra-renal effects
What are 3 general structures that may be damaged leading to Intra-renal acute renal failure?
• which is the most common causes
Glomerulus
Tubular***MOST COMMON
Vascular (vasculitis)
What tubular problem makes the Tubule the most common cause of Intra-renal Acute renal failure?
• what factors contribute to this cause?
• Acute Tubular Necrosis (ATN)
Necrosis is 2º to:
• Ischemic Injury
• Toxic injury from RADIOCONTRAST or medications
What is seen histologically in Acute Tubular Necrosis?
- Denuding of Tubular Epithelial Cells
- PARTICULARLY in the Px. tubules and THICK ascending limb of the lOH
- Muddy Brown Granular Casts occlude the tubular lumen
What urine labs tell you that you’re dealing with Acute Tubular Necrosis?
• Compare these to Pre-renal failure.
• why the difference?
(Intra-renal causes) Acute Tubular Necrosis:
• Urine Osmole between 300-350 (close to plasma conc.)
• Na+ greater than 20
• FeNa+ greater than 1%
Acute Pre-renal failure:
• Urine Osm greater than 500
• Na+ less than 25
• FeNa+ less than 1%
The first situation indicates a problem concentrating urine despite the fact that ADH and Aldosterone are elevated
How do you measure Ischemic Acute Tubular Necrosis?
- Restore Perfusion
- Avoid Nephrotoxins
- Supportive Care
What are some key drugs that cause Pre-Renal Failure?
• what about post renal failure?
Pre-renal:
• NSAIDS
• Ace-Inhibitors
Intrarenal:
• Aminoglycosides
• Amphotericin B
Aminoglycoside Toxicity
• part of tubule that it accumulates in
• Prevention
Accumulates in Proximal Tubule
Prevent toxicity by using ONCE DAILY DOSING
How does Contrast dye cause Intra-renal ARF?
• risk factors
- Direcet Vasoconstrictive effects on arterioles
- Tubular Toxicity
Risk Factors: • Pre-exisiting renal disease • Hrt Failure • Hypovolemia • High dose Contrast
How is Contrast Nephropathy prevented?
- Lower Dose Contrast
- Avoid Closely Spaced Studies
- Avoid volume depletion by giving IV fluids
- Avoid other nephrotoxins
What is Acute Interstitial Nephritis?
• what is often the cause?
Allergic Reaction and infiltration of the kidney with granulocytes OFTEN EOSINOPHILS
Drugs like…
• BETA-Lactams and NSAIDs often cause this
What key findings do you look for in a case of Acute interstitial Nephritis?
- Pyuria
* Eosinophils
If someone has been vomiting there brains out and you need to do a contrast study, what should you do first?
• GIVE them IV FLUIDS to prevent contrast toxicity
