Acute Kidney Injury Flashcards

1
Q

What is the definition of acute kidney injury?

A

An abrupt (within 48 hours) reduction in kidney function, defined as:
• Increase in serum creatinine of > 0.3mg/dL OR
• % increase in serum creatinine of 50% OR
• Oliguria of 6 hours

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2
Q

What is the relationship between acute kidney injury and critical illness?

A

AKI is often found in critically ill patients

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3
Q

What are the 3 groups of AKI causes?

A
  • Prerenal Azotemia
  • Intrinsic Renal Disease
  • Postrenal Obstruction
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4
Q

What are the causes of prerenal azotemia?

A

i. True hypovolemia
ii. Decreased effective circulating volume
iii. Renal artery stenosis/occlusion
iv. NSAID/ACE-I/ARB mechanism

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5
Q

What are the causes of intrinsic renal disease?

A

i. Vascular causes
ii. Glomerular disease
iii. ATN
iv. AIN

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6
Q

What are the causes of postrenal obstruction?

A

i. Bladder outlet obstruction
ii. Bilateral ureteral obstruction
iii. Unilateral ureteral obstruction in a solitary kidney

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7
Q

What are the 2 most common causes of AKI?

A
  • Prerenal Azotemia

- Ischemic ATN

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8
Q

What can prerenal azotemia progress to if it is not corrected?

A

Ischemic ATN

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9
Q

What is prerenal azotemia?

A

It is an appropriate response to renal hypo perfusion that leads to a build up of nitrogen compounds in the blood

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10
Q

What are some of the causes of prerenal azotemia?

A
  • Decreased ECV
  • Renal artery stenosis
  • Drug-induced impaired renal autoregulation
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11
Q

What is the normal renal response to drop in BP?

A
  • Afferent vasodilation

- Efferent vasoconstriction

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12
Q

What is the effect of NSAIDs on the GFR?

A

NSAIDs decrease the GFR by causing afferent arterial vasoconstriction

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13
Q

What is the effect of ACE-I/ARBs on the GFR?

A

They do not affect the GFR that much. They dilate the efferent arterioles which has a protective effect.

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14
Q

What are some of the risk factors for postern disease?

A
  • Older men with prostate disease
  • Solitary kidney
  • Intra-abdominal (pelvic) cancer
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15
Q

What are the 4 categories of intrinsic renal disease?

A
  • vascular causes
  • glomerular diseases
  • acute interstitial nephritis
  • acute tubular necrosis
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16
Q

What are some of the causes of ATN?

A
  • Sepsis
  • Surgery
  • Nephrotoxic exposures
17
Q

What is the major cause of intrinsic renal disease?

A

ATN

18
Q

What are the classical features of ATN?

A
  • Muddy brown urine
  • Oliguric Phase (HTN/Hyperkalemia/Volume Overload)
  • Polyuric Phase
19
Q

What are the two types of ATN?

A
  • Ischemic

- Toxic

20
Q

What are some of the vascular causes of intrinsic renal failure?

A
  • Vasculitis
  • Thromboembolic disease
  • HUS/TTP
  • Malignant HTN
  • Scleroderma renal crisis
21
Q

What is the main vascular cause of intrinsic renal failure?

A

Malignant HTN - which causes impending/progressive organ dysfunction

22
Q

What are the two class of acute interstitial nephritis (AIN) that lead to intrinsic renal failure?

A
Drug Associated (NSAIDs and antibiotics)
Non-drug Associated (Infectious/Autoimmune)
23
Q

What is the triad of signs in AIN?

A

Fever, peripheral eosinophilia, rash

24
Q

Abdominojugular Reflex

A

Pushing on the umbilicus leads to jugular vein rising of more than 4 cm

25
Q

What are signs that the body is too dry?

A
  • Dry mucous membranes
  • Skin tenting (only useful if positive in adults)
  • Neck veins flat at 0 degrees
26
Q

What are signs that the body is too wet?

A
  • Abdominojugular reflux at 30-45 degrees
  • S3 gallop
  • Ascites
27
Q

Prerenal Azotemia Urinanalysis

A

Hyaline Casts

28
Q

Prerenal Azotemia Urine Specific Gravity

A

It will be high - 1.020

29
Q

Prerenal Azotemia Osmolality

A

It will be high - greater than 500

30
Q

Prerenal Azotemia FE of Na

A

It will be low - less than 1%

31
Q

Prerenal Azotemia FE of Urea

A

Less than 35%

32
Q

ATN Urinanalysis

A

Tubular Epithelial Casts

33
Q

ATN Urine Specific Gravity

A

Low

34
Q

ATN Osmolality

A

It will be low - less than 300

35
Q

ATN FE of Na

A

Greater than 2%

36
Q

ATN FE of Urea

A

Greater than 35%

37
Q

What is the BUN:Cr ratio in prerenal azotemia?

A

Greater than 10:1

38
Q

What is the BUN:Cr ratio in ATN?

A

10:1

39
Q

What are the general indications for hemodialysis in acute kidney injury?

A
  • Acidosis (severe and/or refractory)
  • Electrolyte derangement (usually severe ↑K+)
  • Intoxication syndrome (severe, dialyzable)
  • Overload (significant pulmonary edema)
  • Uremia (significantly symptomatic)