Acute Kidney Injury

Question 1

What is definition of acute renal failure?

Answer 1

• Rapid loss of glomerular filtration and tubular function over hours to days
• Retention of urea/creatinine -> Failure of homeostasis
• Oliguric / non-oliguric
• Potentially recoverable

Question 2

What is the definition of acute kidney injury?

Answer 2

Increase in serum creatinine
• ≥ 26.5 μmol/l within 48 hours; or
• ≥ 1.5 times baseline, which has occurred within the prior 7 days; or

Urine volume <0.5 ml/kg/h for 6 hours

Question 3

What is the range for stage AKI 1?

Answer 3

• Serum creatinine: x1.5-1.9 baseline

* Urine: <0.5 for 6-12hrs

Question 4

What is the range for stage AKI 2?

Answer 4

• Serum creatinine: x2-2.9 baseline

* Urine: <0.5 for > 12hrs

Question 5

What is the range for stage AKI 3?

Answer 5

• Serum creatinine: x3 baseline

* Urine: <0.3 for > 24hrs

Question 6

What are the immediate dangerous consequences of AKI?

Answer 6

A - acidosis (can cause cardiac arrest)
E - electrolyte imbalance
I - intoxication TOXINS 
O - overload of fluid and pulmonary oedema --> cardiac arrest 
U - uraemic complications

Question 7

What is the danger of electrolyte imbalance?

Answer 7

Hyperkalaemia can cause cardiac arrest

Question 8

What is the danger of toxin build up?

Answer 8

Opiates can cause respiratory (and the cardiac) arrest

Question 9

What are the three types of causes of AKI?

Answer 9

• Pre-renal - blood flow to kidney
• Renal (intrinsic) - damage to renal parenchyma
• Post-renal - obstruction

Question 10

How do pre-renal causes cause AKI?

Answer 10

Reduce circulative volume causing renal hypoperfusion
• Volume deplete (haemorrhage, dehydration)
• Hypotension / shock
• Congestion cardiac failure / liver failure

• Arterial Occlusion
• Vasomotor: NSAIDs/ACEi

Question 11

How do renal (intrinsic) causes cause AKI?

Answer 11

Consider after pre-renal and obstruction is ruled out:
• Acute tubular necrosis 
• Drugs (NSAIDs, gentamicin)
• Radiocontrast 
• Acute interstitial nephritis  
• Myeloma
• Acute glomerulonephritis

Question 12

How do post-renal causes cause AKI?

Answer 12

Obstruction
• Intraluminal (calculus, clot, sloughed papilla)
• Intramural (malignancy, ureteric stricture, radiation fibrosis, prostate disease)
• Extramural (RPF, malignancy)

Question 13

What is the most common cause of AKI?

Answer 13

Poor perfusion leading to established tubule damage

Failure of the circulation (loss of volume and/or pressure) to provide sufficient plasma flow to maintain blood chemistry and fluid balance

Question 14

What investigations are used for AKI?

Answer 14

• History and examination (fluid status)
• Urine dip stick
• FBC
• USS
• Blood gas (A/B status, potassium and lactate)
• Renal biopsy (histology)

Question 15

What blood tests are carried out for AKIs?

Answer 15

• U+Es, Bicarb, LFTs, bone
• FBC
• Clotting
• ABG

Question 16

How are patients at risk of AKI identified?

Answer 16

S - Sepsis: if suspected screen and treat
T -Toxins: avoid (gentamicin, NSAIDs)
O - Optimise BP and volume status
P - Prevent harm: daily U+Es, fluid balance and med review

Question 17

What is the supportive management of acute kidney injury?

Answer 17

• Fluid balance (restriction if overload)
• Optimise blood pressure (give fluid and stop ACEi)
• Stop nephrotoxic drugs (i.e. NSAIDs, aminoglycoside)

Question 18

What are the ECG changes of hyperkalaemia?

Answer 18

• Peaked T waves (tall tented T waves)
• P wave widen
• PR segment lengthens
• P waves eventually disappear

Question 19

What is the treatment of hyperkalaemia?

Answer 19

• Stabilise myocardium (calcium gluconate)
• Shift K+ into cells (salbutamol, insulin-dextrose)
• Remove K+
- Diuresis
- Dialysis
- Anion exchange resins

Question 20

What is the most common cause of the established tubule damage?

Answer 20

Prerenal (hypotension, hypovolemia):
Failure of the circulation (loss of volume and/or pressure) to provide sufficient plasma flow to maintain blood chemistry and fluid balance –> Acute Tubular Necrosis