Acute Kidney Injury

Question 1

What is the mortality for severe acute kidney injury?

Answer 1

Over 50% for most and up to 80% in the context of multi-organ failure needing dialysis

Question 2

What can be looked at to help diagnose acute kidney injury?

Answer 2

Solute clearance = urea/creatine
Urine output = oliguria
Need for dialysis = increased urea or K+, fluid overload

Question 3

What is acute kidney injury defined as?

Answer 3

Abrupt (<48hrs) reduction in kidney function = absolute increase in serum creatine by >26.4 micromol/l OR increase in creatine by >50% OR a reduction in urine output

Question 4

What can be used to categorise acute kidney injury?

Answer 4

KDIGO staging

Question 5

What are the patient risk factors for acute kidney injury?

Answer 5

Older age, CKD, diabetes, cardiac failure, liver disease, PVD, previous AKI

Question 6

What are some exposure risk factors for acute kidney injury?

Answer 6

Hypotension, hypovolaemia, sepsis, deteriorating NEWS, recent contrast, exposure to certain medications

Question 7

What are the causes of acute kidney injury split into?

Answer 7

Pre-renal (functional), renal (structural) and post-renal (obstruction)

Question 8

What are the causes of pre-renal AKI?

Answer 8

Hypovolaemia = haemorrhage, volume depletion
Hypotension = cardiogenic shock, distributive shock
Renal hypoperfusion = NSAIDs, COX2, ACEi, ARB, hepatorenal syndrome

Question 9

What is the underlying mechanism of pre-renal AKI?

Answer 9

Reversible volume depletion leading to oliguria and increase in creatine

Question 10

What is the urine output of pre-renal AKI?

Answer 10

Oliguria = <0.5 ml/kg/hr

Question 11

How much of the total body weight do the kidneys account for?

Answer 11

0.5% = receive 20% of cardiac output

Question 12

What does pre-renal AKI lead to if left untreated?

Answer 12

Acute tubular necrosis = most common form of AKI in hospital

Question 13

What causes acute tubular necrosis?

Answer 13

A combination of factors leading to decreased renal perfusion = sepsis, severe dehydration, rhabdomyolysis, drug toxicity

Question 14

How can the hydration of a patient with pre-renal AKI be assessed?

Answer 14

BP, heart rate, urine output, JVP, capillary refill time, oedema, pulmonary oedema

Question 15

How may a patient with pre-renal AKI undergo fluid challenging for hypovolaemia?

Answer 15

Crystalloid (0.9% NaCl) or colloid (Gelofusion), don’t use 5% dextrose, give bolus of fluid then reassess and repeat as necessary, if >1L IN and no improvement seek help

Question 16

What is renal AKI?

Answer 16

Diseases causing damage or inflammation to cells = categorised by structure (blood vessels, glomerular, interstitial, tubular)

Question 17

What are some causes of vascular renal AKI?

Answer 17

Vasculitis, renovascular disease

Question 18

What causes glomerular renal AKI?

Answer 18

Glomerulonephritis

Question 19

What are some causes of interstitial renal AKI?

Answer 19

Nephritis due to drugs, infection (TB) or systemic disease (sarcoid)

Question 20

What are some causes of tubular renal AKI?

Answer 20

Ischaemia (prolonged renal hypoperfusion), gentamicin, contrast, rhabdomyolysis

Question 21

What are some non-specific symptoms of renal AKI?

Answer 21

Anorexia, weight loss, fatigue/lethargy, nausea and vomiting, itch, oedema and SOB due to fluid overload

Question 22

What are some signs of renal AKI?

Answer 22

Hypertension, oedema, pleural/pulmonary effusion, uraemia (itch, pericarditis), oliguria

Question 23

What are some clues that AKI might have a renal cause?

Answer 23

Sore throat, rash, joint pain, diarrhoea, vomiting, haemoptysis, recent contrast, eosinophilia, vascular bruit

Question 24

What are some investigations done for renal AKI?

Answer 24

U & Es = marker for renal function, is K+ high?
FBC and clotting screen = abnormal clotting, anaemia
Urinalysis = haematoproteinuria
Immunology = ANCA, ANA, GBM
USS, protein electrophoresis, BJP

Question 25

How is renal AKI treated?

Answer 25

Establish good perfusion pressure = inotropes/vasopressors, fluid Treat underlying cause and stop nephrotoxics Dialysis if still uraemic/anuric

Question 26

What are some complications of renal AKI?

Answer 26

Hyperkalaemia, pulmonary oedema, fluid overload, severe acidosis (pH <7.5), uraemic pericardial effusion, severe uraemia (>40)

Question 27

What is the underlying mechanism of post-renal AKI?

Answer 27

Obstruction of urine flow leads to back pressure (hydronephrosis) and thus loss of concentrating ability

Question 28

What are some causes of post-renal AKI?

Answer 28

Calculi, cancer, strictures, extrinsic pressure

Question 29

How is post-renal AKI treated?

Answer 29

Relieve obstruction = catheter, nephrostomy | Refer to urology if ureteric stenting needed

Question 30

What is hyperkalaemia associated with?

Answer 30

Cardiac arrhythmias = peaked T waves on ECG

Question 31

What is the normal range for potassium?

Answer 31

3.5-5

Question 32

What is hyperkalaemia defined as?

Answer 32

Quantities >5.5 | Life threatening if >6.5

Question 33

How is hyperkalaemia assessed?

Answer 33

ECG and muscle weakness

Question 34

How can the heart be protected from hyperkalaemia?

Answer 34

Protect the myocardium by giving 100ml of 10% of calcium gluconate (2-3 mins)

Question 35

How is hyperkalaemia treated?

Answer 35

Move K+ back into cells = insulin (actrapid 10 units) with 50ml of 50% dextrose (30 mins), nebulised salbutamol (90 mins)

Question 36

How is absorption of potassium from the GI tract during hyperkalaemia prevented?

Answer 36

Give calcium resonium (not in an acute setting)

Question 37

What are some urgent indications for haemodialysis?

Answer 37

Hyperkalaemia >7 or >6.5 if unresponsive to therapy Severe acidosis = pH <7.15 Fluid overload Urea >40 (pericardial rub/effusion)

Question 38

What is the mortality of AKI?

Answer 38

AKI alone = 10-30% AKI with one other organ dysfunction = 30-50% AKI as part of multi-organ failure = 70-90%

Question 39

What is the recovery rate of renal function after AKI?

Answer 39

10-15% have no recovery of renal function | 5-10% recover but have progressive CKD

Question 40

Can dialysis reverse disease course?

Answer 40

No = it clears toxins but doesn't alter the course of disease