Acute Kidney Injury L14

Question 1

What is acute kidney injury?

Answer 1

A rapid (hours to days) decline in kidney function.

Question 2

Why is creatinine used to measure AKI rather than eGFR?

Answer 2

eGFR is not an accurate measurement if kidney function is changing over a short period of time

Question 3

describe the stages of AKI in terms of creatinine levels and urine output.

Answer 3

Stage 1:

• > 26microM increase (50-100% from baseline) creatinine
• <0.5ml/kg/hour urine output for 6 hours

Stage 2:

• 100-200% increase in creatinine
• <0.5ml/kg/hour for 12 hours

Stage 3:

• > 200% increase or >345microM
• <0.3ml/kg/hour for 24 hours or anuria for 12 hours

*stage 3 is the most severe and patients tend to decline from stage 1 to stage 3

Question 4

Who is at risk of Acute Kidney Injury?

Answer 4

• old age
• diabetes mellitus
• hypertension
• heart disease
• liver disease
• CKD
• medication: diuretics, ACEi/ARB, NSAIDs, Gentamicin, vancomycin, chemotherapy

Question 5

what are the three types of causes of AKI?

Answer 5

• pre-renal
• renal
• post-renal

Question 6

What is the main pre-renal cause of AKI?

Answer 6

perfusion failure

Question 7

What conditions can lead to perfusion failure in the kidney?

Answer 7

• hypotension
• hypovolaemia
• renal artery occlusion
• can be made worse by
• RAS blockade
• NSAIDs
• antihypertensives
• diuretics

Question 8

What is the autoregulatory range?

Answer 8

The range of systolic blood pressures through which blood flow to the kidney remains relatively constant (due to changes in efferent and afferent arterioles)

Question 9

If blood pressure and blood volume are high, what happens to the renal perfusion rate and urine production?

Answer 9

• renal perfusion rate increases
• urine production remains normal

*still within autoregulatory range

Question 10

If blood pressure and blood volume are normal, what happens to the renal perfusion rate and urine production?

Answer 10

• renal perfusion and urine production are both normal

* within autoregulatory range

Question 11

If blood pressure and blood volume are low (but within autoregulatory range), what happens to the renal perfusion rate and urine production?

Answer 11

• renal perfusion and urine production are normal - autoregulated

Question 12

If blood volume and blood pressure are very low, what will happen to the renal perfusion rate and urine production?

Answer 12

• renal perfusion and urine production decrease - out of autoregulatory range > cannot be regulated > problems with kidney function and homeostasis

Question 13

List the different molecules used to block RAAS.

Answer 13

• renin inhibitors (binds to renin to stop conversion > At1)
• ACE inhibitors
• mineralocorticoid receptor antagonist (blocks aldosterone)
• At2 receptor blockers

Question 14

What is the purpose of RAAS blockade?

Answer 14

• stop arteriolar constriction
• stop rise in blood volume

> stop rise in BLOOD PRESSURE

Question 15

In a normal kidney at high blood pressure, what happens to the afferent and efferent arterioles to maintain renal perfusion across glomerulus?

Answer 15

afferent - constricts

efferent - relative dilation

Question 16

In a normal kidney at low blood pressure, what happens to the afferent and efferent arterioles to maintain renal perfusion across glomerulus?

Answer 16

afferent - dilates

efferent - constricts

Question 17

How does RAAS blockade decrease renal perfusion?

Answer 17

inhibits efferent arteriolar constriction so at low blood pressure, lose perfusion across glomerulus

Question 18

How do NSAIDs stop decrease perfusion?

Answer 18

inhibit afferent arteriolar dilation (constrict vessels) so at low blood pressure, perfusion across glomerulus not maintained as it would normally

Question 19

What is the treatment of perfusion failure?

Answer 19

• treat underlying cause
• fluid replacement
• BP support (inotropic drugs e.g.NA/A)
• restore arterial patency (taking clots out, stents etc.)
• stop RAS blockade
• stop NSAIDs

Question 20

What is the main post-renal cause of AKI?

Answer 20

obstruction in kidney/urinary tract

Question 21

What is the treatment of obstruction?

Answer 21

• bypass or remove obstruction
• nephrostomy (urine from renal pelvis > bag outside body)
• bladder catheter
• lithotripsy (destruction of stones)
• take out tumours
• dilate strictures

Question 22

What are the renal causes of AKI?

Answer 22

diseases that damage

• tubules
• glomerulus
• interstitium

Question 23

systemic renal causes of AKI?

Answer 23

vasculitis, SLE (lupus), myeloma

Question 24

infectious renal causes of AKI?

Answer 24

HIV, endocarditis

Question 25

allergic renal causes of AKI?

Answer 25

acute interstitial nephritis

Question 26

other renal causes of AKI?

Answer 26

drug toxicity - gentamycin, NSAID, chemotherapy

Glomerulonephritis

Question 27

What is systemic vasculitis?

Answer 27

a type of vasculitis that destroys blood vessels through inflammation. A subgroup of this is ANCA associated vasculitis - it is a rare disease and airway and renal organs are most commonly affected.

ANCA = anti-neutrophil cytoplasmic antibody

Question 28

What are the treatments for inflammatory renal disease? What are the complications with each?

Answer 28

• steroids - diabetes, infection, osteoporosis, skin damage, weight gain
• cyclophosphamide - infections, malignancy, bone marrow supression, infertility
• plasma exchange - infection, bleeding, risks of central lines
• azathioprine/mycophenolate - infection, cancer, liver abnormalities

Question 29

What are the main causes of death in AKI?

Answer 29

• underlying disease
• infection
• hyperkalaemia
• acidosis
• pulmonary oedema