AKI

Question 1

What is the definition of AKI?

Answer 1

1. Increase in Cr higher than 0.3 mg/dl (26.5 umol/L) in 48 hours
2. A rise in Cr >1.5 times the baseline.
3. A decrease of urine volume =/< than 0.5 mg/kg/hr
   If one or more of the criteria are met, the patient can be diagnosed with AKI.

Question 2

What occurs during AKI?

Answer 2

1. When a patient is in AKI there is a rapid decrease in the glomerular filtration rate which allows a build up of waste: nitrogen, Cr and urea.

Question 3

Why does pre-renal failure occur?

Answer 3

1. Pre renal failure occurs due to poor nephron perfusion.

Question 4

What conditions contribute to pre-renal failure?

Answer 4

1. Shock
2. hypotension
3. sepsis
4. over diuresis
5. heart failure
6. cirrhosis
7. bilat renal artery stenosis
8. solitary functioning kidney which is worsened by ACE and other drugs
   NSAIDS, calcineurin inhibitors, diuretics

Question 5

Acute kidney injury can be divided into vascular/interstitial/glomerular and tubular, of the aforementioned, which is the most common cause of AKI?

Answer 5

1. Tubular necrosis

Question 6

What causes acute tubular necrosis?

Answer 6

1. Prolonged ischemia

Question 7

What are some intrinsic causes of AKI?

Answer 7

1. Underlying diseases such as lupus, wegner and good pasture syndrome. Rheumatological disease and systemic illnesses

Question 8

With underlying disease that can cause AKI like lupus and RA what is the reason AKi occurs?

Answer 8

1. AKI occurs due to inflammation of the renal vasculature and glomeruli

Question 9

What occurs in the body when there is hypotension or poor systemic perfusion?

Answer 9

1. Baroreceptors in the arteries and heart receptors respond to these changes by increasing sympathetic tone, the afferent arterioles sense the decrease in perfusion which leads to an increase in renin secretion and the antidiuretic hormone secretion.

Question 10

How long can the afferent arteriole maintain adequate perfusion?

Answer 10

1. The afferent arterioles can maintain adequate perfusion until the SBP drops below 80 mmhg

Question 11

What is Renin?

Answer 11

1. A protein enzyme released by the juxtaglomerular cells in the afferent arteriolar wall.

Question 12

What exactly does Renin do?

Answer 12

1. Renin converts Angiotensin 1 to angiotensin 2

Question 13

What does Angiotensin 2 do?

Answer 13

Angiotensin 2 increases Aldosterone synthesis

Question 14

When Angiotensin 2 increase Aldosterone synthesis, what happens next?

Answer 14

1. Increased aldosterone synthesis causes vasoconstriction and sympathetic nervous system stimulation.

Question 15

When there is a mild to moderate decrease in cardiac output what does angiotensin 2 do?

Answer 15

1. Angiotensin 2 works on the efferent arteriole to maintain filtration fraction

Question 16

What would cause Angiotensin 2 to constrict the afferent arteriole and further decease GFR?

Answer 16

1. If there is a drop in cardiac output followed by another decrease, then Angiotensin 2 would cause further restriction by increasing vasocontraction of the afferent arteriole

Question 17

In pre renal AKI what should the urine sodium level be?

Answer 17

1. 20 mEq/L

Question 18

What is a better predictor of AKI when evaluating U/A results?

Answer 18

1. Fractional excretion of sodium, this is not affected by urine out and it measures on the percent of Na+ excreted. FENa is usually less than 1% in AKI and greater than 2% in ATN

Question 19

What is the gold standard for differentiating pre-renal failure from other causes of AKI?

Answer 19

1. Fluid administration, when volume is replenished the Cr should trend down toward the patients baseline within 24-72 hours.

Question 20

How is volume replenished in AKI?

Answer 20

1. with Isotonic saline

Question 21

With ATN how does the Cr rise?

Answer 21

1. By 0.3 to 0.5 mg/dl per day in pre renal the rate will be slower.