AKI

Question 1

What is the definition of acute kidney injury?

Answer 1

A rapid decline in kidney function within a short period of time.

Question 2

What criteria is used to stage AKI?

Answer 2

KDIGO criteria

Question 3

Stages of serum creatinine in KDIGO criteria?

Answer 3

Stage 1: Increase >/= 26 micromol/l within 48 hours or increase >/= 1.5 to 1.9 baseline serum creatinine.

Stage 2: Increase 2-2.9 baseline serum creatinine

Stage 3: Increase >/= 3x baseline serum creatinine or is commenced on renal replacement therapy regardless of stage.

Question 4

Stages of urinary output in KDIGO criteria?

Answer 4

Stage 1: less than 0.5ml/kg/hour for 6-12 hours

Stage 2: less than 0.5ml/kg/hour for more than/equal to 12 hours

Stage 3: less than 0.3ml/kg/hour for more than 24hrs or anuria (lack of urine production) for more than 12 hours.

Question 5

Commonest form of AKI in hospital setting?

Answer 5

Renal AKI, specifically acute tubular necrosis

Question 6

What is acute tubular necrosis?

Answer 6

• Tubular cell death
• Commonest form of AKI in hospital
• Occurs due to a number of factors resulting in decreased renal perfusion.
• Common causes include: sepsis and severe dehydration
  *Other important causes include: Rhabdomyolysis and drug toxicity

Question 7

Examples of drugs causing acute tubular necrosis

Answer 7

NSAID’s
Antibiotics I.e. aminoglycosides, vancomycin etc.
Radiocontrast agents

Question 8

What is acute interstitial nephritis?

Answer 8

• Another type and cause of renal AKI
• Characterised by inflammatory infiltrate in the kidney interstitium.
• Associated with medications, infections and systemic diseases.
• Associated with: NSAID’s, antibiotics i.e. penicillins (amoxicillin), ciprofloxacin

Question 9

What is hyperkalaemia?

Answer 9

High serum potassium; associated with cardiac arrhythmias.

Question 10

Causes of hyperkalaemia

Answer 10

AKI (acute kidney injury)
CKD (chronic kidney disease)
Rhabdomyolysis
Adrenal insufficiency (Addison’s disease)

Question 11

Medications associated with hyperkalaemia

Answer 11

ACE inhibitors
Aldosterone antagonists (spironolactone and epleronone)
ARB’s (angiotensin receptor blockers)
NSAID’s
Potassium supplements

Question 12

Symptoms of hyperkalaemia

Answer 12

Non-specific symptoms - mainly relating to cardiac or muscular function, such as:
* Fatigue
* Muscle weakness
* Palpitations/chest pain

Question 13

Investigations for hyperkalaemia

Answer 13

Bloods
- U and E’s (potassium, creatinine, urea and eGFR)

ECG

Question 14

Appearance of hyperkalaemia on ECG

Answer 14

Tall peaked T-waves
Flattened or absent p waves
Broad QRS complexes

Question 15

Management of hyperkalaemia

Answer 15

• Cardiac monitor and IV access
• Treat with insulin and dextrose infusion and IV calcium gluconate (calcium chloride used if calcium gluconate is unavailable).
• 10ml 10% calcium gluconate (2-3 min) - to protect myocardium.
• Insulin with 50ml 50% dextrose (30 mins) - moves K+ back into the cell from the ECF (extracellular fluid).

Question 16

What is Rhabdomyolysis?

Answer 16

Condition where skeletal muscle tissue breaks down and releases breakdown products into the blood. Usually triggered by an event that causes the muscle to break down e.g. extreme underuse or extreme overuse or a traumatic injury.

Question 17

Main causes of Rhabdomyolysis

Answer 17

Anything that can cause significant damage to the muscle cells. This can include:
* Prolonged immobility, particularly frail patients that fall and spend time on the floor before being found.
* Extremely rigorous exercise beyond person’s fitness level (e.g. ultramarathon etc).
* Crush injuries
* Seizures

Question 18

What is the pathophysiology of Rhabdomyolysis?

Answer 18

Muscle cells (myocytes) undergo apoptosis resulting in the release of myoglobin, phosphate, creatine kinase and potassium (the most dangerous breakdown product as it can lead to arrhythmias).

These products are filtered through the kidney in high concentrations - resulting in AKI.

Question 19

Clinical presentation for rhabdomyolysis

Answer 19

Muscle aches and pains
Oedema
Brown-red urine
Fatigue
Confusion (especially in older frail patients).

Question 20

Investigations for rhabdomyolysis

Answer 20

Creatine kinase (raised)

Urine: will be red-brown in colour due to myoglobinuria (will be positive for blood)

Urea and electrolytes for AKI and hyperkalaemia

ECG is important in assessing the hearts response to high potassium levels.

Question 21

What are the types of AKI?

Answer 21

Pre - renal (occurring before the kidneys) - lack of perfusion to kidneys.

Renal aka intrinsic (occurring within the kidneys) - affects components of nephron directly.

Post - renal (occurring below the kidneys) - obstruction to urinary flow beyond kidney.

Question 22

Causes of pre - renal AKI

Answer 22

1) Hypovolaemia: low blood volume
- GI loss e.g. vomiting, diarrhoea.
- Haemorrhage
- Burns

2) Hypotension: low blood pressure
- Cardiogenic
- Distributive i.e. anaphylaxis, sepsis.
- Obstructive i.e. pulmonary embolism.

Question 23

Causes of intrinsic AKI

Answer 23

1) Drugs - NSAID’s, ACEi’s/ARB’s.

2) Acute tubular necrosis

3) Acute interstitial nephritis

4) Glomerular disease i.e. anti-GBM disease, post-streptococcal glomerulonephritis.

5) Vascular events i.e. thrombosis/embolism.

Question 24

Causes of post - renal AKI

Answer 24

1) External (outside the urinary system) i.e. BPH, tumour.

2) Internal (within the urinary system) i.e. stricture, renal stones (more uncommon as will only affect one kidney), urinary tract tumours.

Question 25

Treatment of AKI

Answer 25

1) IV fluid resuscitation

2) Stop nephrotoxic medications i.e. diuretics, ACE inhibitors, metformin and NSAID’s.

3) Correct the electrolyte imbalance. Hyperkalaemia treat with IV calcium gluconate + Insulin + Dextrose

4) Urinary catheter - monitor urine output and monitor weight.

5) Renal replacement therapy
- Haemodialysis is indicated for: AEIOU
* Severe Acidosis (despite treatment)
* Electrolyte abnormalities i.e. Hyperkalaemia (despite treatment)
* Drug Intoxications
* Oedema (overload of fluid)
* Ureamic pathology (encephalopathy, pericarditis, anorexia, neuropathy and asterisix)

Question 26

What are the indications for dialysis

Answer 26

Remember: AEIOU

A - Acidosis pH > 7.20
E - Electrolyte abnormalities includes K+ over 7 mmol/l
I - Intoxication
O - Oedema
U - Ureamic pathology i.e. encephalopathy, pericarditis.