Acute Kidney Injury

Question 1

What is AKI?

Answer 1

A rapid drop in kidney function, diagnosed by measuring serum creatinine

Question 2

What are the NICE guidelines for diagnosing an AKI?

Answer 2

Rise in creatinine of more than 25micromol/L in 48 hours
Rise in creatinine of more than 50% in 7 days
Urine output of less than 0.5ml/kg/hour over at least 6 hours

Question 3

What is the KDIGO criteria for staging AKI?

Answer 3

Stage 1: Increase in creatinine to 1.5-1.9 times baseline, or
Increase in creatinine by ≥26.5 µmol/L, or
Reduction in urine output to <0.5 mL/kg/hour for ≥ 6 hours
Stage 2: Increase in creatinine to 2.0 to 2.9 times baseline, or
Reduction in urine output to <0.5 mL/kg/hour for ≥12 hours
Stage 3: Increase in creatinine to ≥ 3.0 times baseline, or
Increase in creatinine to ≥353.6 µmol/L or
Reduction in urine output to <0.3 mL/kg/hour for ≥24 hours

Question 4

What are risk factors for AKI?

Answer 4

• Old age
• Sepsis
• CKD
• Diabetes
• Heart failure
• Liver disease
• Medications including NSAIDs, gentamicin, diuretics and ACE

Question 5

What are causes of AKI?

Answer 5

Pre-renal: Insufficient blood supply e.g. dehydration, shock or heart failure
Renal: Intrinsic disease e.g ATN, Glomerulonephritis, HUS, Rhabdomyolysis
Post renal: Obstruction to the outflow of urine e.g kidney stones, tumours, strictures of the urethra, BPH

Question 6

How does AKI present?

Answer 6

• Reduced urine output
• Pulmonary or peripheral oedema
• Arrhythmias secondary to changes in K+
• Uraemia

Question 7

What are the investigations for AKI?

Answer 7

• Urinalysis: leucocytes and nitrites suggests infection, protein and blood suggest acute nephritis, glucose
• US scan

Question 8

What are management of AKI?

Answer 8

• IV fluids (fluid challenge)
• Withhold medications which worsen the condition e/g NSAIDs, ACE, ARB, Diuretics
• Withhold medications which can become toxic in AKI e.g. metformin, opiates, lithium
• Relive obstruction
• Dialysis in severe cases e.g. uraemia (encephalopathy or pericarditis) or pulmonary oedema

Question 9

What is the treatment for hyperkalaemia?

Answer 9

• IV Calcium gluconate
• Combined insulin/dextrose infusion or nebulised salbutamol which shift potassium from extracellular to intracellular compartment
• Calcium gluconate only stabilises the myocardium and does NOT lower potassium levels
• Calcium resonium can be used to remove potassium from the body

Question 10

What are complications of AKI?

Answer 10

• Fluid overload
• Hyperkalaemia
• Metabolic acidosis
• Uraemia which can lead to encephalopathy and pericarditis

Question 11

Which drugs should be stopped in an AKI?

Answer 11

Diuretics
ACE inhibitors
ARBs
Metformin (toxicity)
NSAIDs

DAAMN

Question 12

What is the most common renal cause of AKI?

Answer 12

Acute tubular necrosis

Question 13

What are the features of acute tubular necrosis?

Answer 13

Damage to tubular cells due to prolonged ischaemia or toxins
Kidneys can no longer concentrate urine or retain sodium - urine osmolality low, urine sodium high
Muddy brown casts

Question 14

What is a potential complication of fluid resuscitation?

Answer 14

Use of 0.9% Sodium Chloride for fluid therapy in patients requiring large volumes = risk of hyperchloremic metabolic acidosis