AKI

Question 1

define acute kidney injury

Answer 1

• abrupt loss of kidney function resulting in
  
  • retention of urea and other nitrogenous waste products
  • dysregulation of volume status and electrolytes

Question 2

GFR

Answer 2

estimates how much blood passed through the glomeruli each minute to be filtered

Question 3

what are the criteria for diagnosis of acute kidney injury

Answer 3

1. serum creatinine levels
2. decrease in urine output

Question 4

can you still use serum creatinine to assess kidney function in patient undergoing dialysis

Answer 4

no, creatinine is removed by dialysis

Question 5

Define the RIFLE acronym

Answer 5

• Risk
• Injury
• Failure
• Loss
• ESRD
• *first three are levels of severity; last two are outcome measures

Question 6

what three groups have come up with ways to define AKI

Answer 6

• RIFLE
• AKIN
• KDIGO

Question 7

what is RIFLEs definition of AKI using serum creatinine

Answer 7

• increase in serum creatitine > 50% developing over 7 days

Question 8

what is AKIN’s definition of AKI using serum creatinine

Answer 8

• increase in serum creatinine of 0.3 mg/dL pr > 50% developing over 48 hours

Question 9

AKI can be classified into what 3 categories

Answer 9

1. Prerenal: decreased renal perfusion
2. Intrinsic renal: pathology of vessels, glomeruli, or tubules-interstitium
3. Postrenal: obstructive

Question 10

What are some causes of Prerenal AKI

Answer 10

1. True volume depeletion
   
   • V/D; burns, third spacing from crush injury
2. Hypotension
   
   • shock or aggressive tx of HTN
3. Edematous status
   
   • heart failure, cirrhosis
4. Bilateral renal artery stenosis
5. Drugs affecting GFR
   
   • NSAIDs

Question 11

What are some causes of Intrinsic renal AKI

Answer 11

• renal ischemia
  
  • from all causes of severe prerenal dz
• sepsis
• nephrotoxins
  
  • aminoglycosides, IV contrast, rhabdomyolysis

Question 12

How does IV contrast affect kidneys

Answer 12

• causes renal tubular epithelial cell toxicity and renal medullary ischemia

Question 13

risk factors for kidney damage by IV contrast

Answer 13

• pre-existing renal disease
• volume depletion
• repeated doses of contrast

Question 14

prevention of kidney damage by IV contrast

Answer 14

• hydration
• avoidance of nephrotoxic drugs for at least 48 hours after exposure
  
  • e.g metformin

Question 15

define Nonoliguric

Answer 15

>400 mL/24 hours

Question 16

Define Oliguric

Answer 16

<400mL/24 hr

Question 17

define Anuric

Answer 17

<100mL/24 hr

Question 18

important labs to get when evaluating AKI

Answer 18

• UA
• creatinine
  
  • calculation of GFR
  • calculatoin of fractional excretion of sodium (FENa)

Question 19

first line imaging to get when evaluating AKI? what are you evaluating for

Answer 19

• renal US
• assess for urinary tract obstruction

Question 20

most dipsticks permit the analysis of the following core urine parameters

Answer 20

• Heme
• Leukocyte esterase
• Nitrite
• Albumin
• Hydrogen ions (pH)
• specific gravity
• Glucose

Question 21

muddy brown casts are pathognomonic for

Answer 21

Acute tubular necrosis

Question 22

What are the two most commonly used equations for calculating GFR

Answer 22

• Crockcroft-Gault
• Modification of Diet in renal disease (MDRD)

Question 23

how is the fractional excretion of sodium (FENa) used

Answer 23

• measures urine sodium
• in an oliguric patient, the FENa may help to distinguish prerenal AKI from intrinsic renal pathology

Question 24

what is the equation for fractional excretion of sodium (FENa)? What values suggest prerenal and ATN?

Answer 24

FENa = (urine Na / Serum Na) / (Urine Cr / Serum Cr) x 100

• < 1% suggests prerenal etiology
• >2% suggests intrarenal (ATN)

Question 25

when can you not rely on the fractional excretion of sodium (FENa) equation

Answer 25

* cannot be used in patients on diuretics * can't be used with chronic renal failure * only useful in acute renal failure

Question 26

When is a renal biopsy indicated

Answer 26

* for patients who have no clear explanation for AKI * if the creatinine is markedly elevated or if it significantly worsens over the course of days * biopsy will provide more definitive tissue diagnosis

Question 27

contraindications to getting a renal biopsy

Answer 27

* solitary native kidney * bleeding diathesis * hydronephrosis * pyelonephritis * renal tumor

Question 28

List the life-threatening complications that can come from AKI

Answer 28

* volume imbalance: depletion or overload * metabolic acidosis * hyperkalemia * hypocalcemia * hyperphosphatemia * uremia * \*\*generally require hemodialysis

Question 29

if patient has a h/o consistent with fluid loss (V/D), a physical exam consistent with hypovolemia (hypotension, tachycardia) and/or oliguria, treatment is

Answer 29

* IV fluids * fluid challenge attempts to identify prerenal failure * crystalloid isotonic fluid (0.9 nml saline) is preferred

Question 30

how much fluid is given

Answer 30

* begin with 1-3 liters of fluid with careful and repeated clinical assessment * pts who do not respond to fluids are unlikely to have prerenal disease

Question 31

if patient becomes volume overloaded or develops fluid retention from IV fluid therapy then treatment is

Answer 31

* diuretics (typically furosemide) = temporizing measure * should not be prolonged therapy * dialysis offers most efficient method of volume removal

Question 32

how does AKI lead to metabolic acidosis

Answer 32

* excretion of acid and regeneration of bicarbonate is **impaired with a low GFR** * causes of AKI such as sepsis, trauma, and multi-organ failure produces increased amount of acid

Question 33

how does diarrhea worsens metabolic acidosis

Answer 33

causes net loss of bicarbonate

Question 34

treatment options for metabolic acidosis from AKI

Answer 34

1. dialysis 2. bicarbonate administration * choice depends on presence of volume overload and the underlying cause of acidosis

Question 35

when should a patient with metabolic acidosis from AKI be dialyzed

Answer 35

* patients with severe **oligo-anuric AKI** who are **volume overloaded** and have severe metabolic acidosis ( **pH \<7.1**) * bicarb adminstration results in large sodium load that may cause or increase volume overload

Question 36

when should a patient with metabolic acidosis from AKI be given bicarbonate

Answer 36

* patients with AKI who are **not volume overloaded** and * acidosis is related to **diarrhea** * pH \< 7.1 and awaiting dialysis * AKI due to **rhabdomyolysis** * **goal: serum bicarb 20-22 mEq/L and pH \> 7.2**

Question 37

hyperkalemia can cause

Answer 37

* impaired neuromuscular transmission * cardiac conduction abnormalities (arrhythmias)

Question 38

how does AKI cause hypocalcemia and hyperphosphatemia

Answer 38

* increases in serum phosphorus levels is caused by reduced GFR * phosphorus binds to calcium -\> hypocalcemia * \*\*serum ionized calciu, should be measured

Question 39

what is the tx for patients who are symptomatically hypocalcemic but whose phosphate levels are very high?

Answer 39

* dialysis * if you give IV calcium, it may result in deposition of calciu, phosphate into vasculature and organs * however, give IV calcium while waiting for dialysis if pt has tetany, QT prolongation, Chvostek sign

Question 40

Name signs/symptoms of severe hypocalcemia

Answer 40

* tetany * confussion, sz * Trousseau's sign * Chovstek sign * QT prolongation

Question 41

patients with serum phosphate levels \> 6 mg/dL should be treated with

Answer 41

**dietary phosphate binders** * if serum ionized ca2+ is low =\> **calcium acetate** or calcium carbonate * if serum ionized ca2+ is high =\> **aluminum hydroxide**

Question 42

dialysis should be initiated in patients with severe uremia. what are some signs of severe uremia

Answer 42

* pericarditis * neuropathy * unexplained decline in mental status