Acute Kidney Injury

Question 1

What is the rough definition of AKI and the different stages?

Answer 1

• It is the decline of renal excretory function over hours/days with a rise in serum urea and creatinine.
  Stage 1- Creatinine raised by 50% of baseline.
  Stage 2 - Serum creatinine double the baseline
  Stage 3 - Serum creatine 3x the baseline

Question 2

What is oliguria?

Answer 2

Infants - Less than 1mL/kg/hour
Adults - Less than 0.5mL/kg/hour.
Roughly less than 400-500ml per 24 hours

Question 3

What is an AKI E-Alert?

Answer 3

When the lab identifies a change in serum creatinine, they will notify the doctor. Occurs when the serum creatinine is 50% higher than previous tests

Question 4

What the categories for the different causes of AKI?

Answer 4

Pre-renal - Circulatory failure.
Renal - cells of the kidney.
Post-renal - obstruction

Question 5

What are some causes of pre-renal AKI?

Answer 5

1. Hypovolaemia and hypotension (could be due to diarrhoea/vomiting, inadequate fluid intake, blood loss)
2. Reduced effective circulatory volume (cardiac failure or sepsis)
3. Drugs such as ACEi or NSAIDs.
4. Renal artery stenosis

Question 6

What are some renal causes of AKI?

Answer 6

1. Acute tubular Necrosis (often occurs due to untreated pre-renal causes (ischaemia) or toxins).
2. Untreated obstructive AKI,
3. Glomerulonephritis,
4. Acute tubulointerstitial nephritis,
5. Vasculitis,
6. Atherothrombolic

Question 7

What are some causes of post renal AKI?

Answer 7

Obstructive things such as calculi, tumours, lymphnodes, prostate. In men THINK PROSTATE, and in women gynae cancers.

Question 8

What are the causes of acute tubular necrosis?

Answer 8

• ATN is always caused by under perfusion of tubules and/or toxicity. So it can be caused by hypoperfusion, sepsis, toxins or all three

Question 9

What are some toxins which can cause acute tubular necrosis?

Answer 9

Exogenous - Drugs (Gentamicin, NSAIDs or ACEi), contrast or poisons such as metals/antifreeze.
Endogenous - Myoglobin (rhabdomyolysis), haemoglobin, immunoglobins, calcium or urate.

Question 10

What occurs to the renal arteries when blood pressure falls?

Answer 10

• Prostaglandins trigger vasodilation of the afferent arteriole (increase blood flow into glomeruli)
  -Angiotensin causes vasoconstriction of the efferent arteriole to increase the blood pressure

Question 11

Explain how NSAIDs and ACE inhibitors can affect the kidneys?

Answer 11

NSAIDs - prevent prostaglandin release and therefore stop the dilation of afferent arterioles with hypotension.
ACEi - Stop vasoconstriction of efferent arterioles during hypotension

Question 12

What is the management of AKI?

Answer 12

• Bloods: Check potassium, if hyperkalaemia then manage asap. Look at urea and creatine.
• Measure urine output,
• Clinical assessment of fluid status
• Remove causes (drugs or sepsis) and exclude obstruction so get an ultrasound. If cause unknown then urinalysis, GN screen, blood films.

Question 13

What is involved in a glomerulonephritis screen?

Answer 13

• ANA,
• ANA,
• Immunoglobulins,
• Complement,
• Anti-glomerular basement membrane antibodies,
• Urine bence jones proteins

Question 14

What can be seen on a renal ultrasound?

Answer 14

• Obstructions,.
• Size of kidneys,
• Loss of corticomedullary differentiation which suggests CKD.

Question 15

What potassium levels are concerning?

Answer 15

• If K+ is between 6.0-6.4 then ECG needed as there is risk of arrhythmias.
• If K+ is over 6.5 then it is a medical emergency

Question 16

What is the treatment of hyperkalaemia?

Answer 16

• Calcium resonium (reduce K+ absorption from gut)
• Short acting insulin +50ml of 50% dextrose (moves K+ into cells but be careful)
• Calcium gluconate (stabilises cardiac membrane while you treat hyperkalaemia, should be given first)

Question 17

How can you treat hyperkalaemia and low bicarb?

Answer 17

Bicarb supplementation, if bicarb is less than 16 and patient is acidotic

Question 18

What are the absolute and relative indications for dialysis?

Answer 18

Absolute - Refractory potassium over 6.5 mmol or refractory (stubborn) pulmonary oedema.
Relative - Acidosis (pH<7.1), Uraemia (esp if >40) and toxins such as lithium.

Question 19

What can occur when recovering from acute tubular necrosis?

Answer 19

There is a polyuric phase for 48-72 hours where the kidneys can produce up for 6L of urine per day. It requires careful monitoring of electrolytes.

Question 20

What is the mnemonic for the indications for acute dialysis in patients with severe AKI?

Answer 20

AEIOU
- Acidosis (severe and unresponsive to treatment)
- Electrolyte abnormalities (severe and unresponsive hyperkalaemia),
- Intoxication,
- Oedema (severe and unresponsive to treatment)
- Uraemia symptoms such as seziure