Intro to Acute Kidney Injury (AKI)

Question 1

What is the definition of AKI?

Answer 1

AKI - Acute Kidney Injury.

• ‘The syndrome arising from a rapidly falling GFR’

Characterised by retention of both nitrogenous (e.g. urea and creatinine) and non-nitrogenous waste products,

• As well as disordered electrolyte, acid-base and fluid homeostasis.

Question 2

How is AKI diagnosed?

(Physiologically speaking)

Answer 2

AKI present if:

Serum creatinine:

• ≥26.5 μmol/l in ≤48h.
  
  • OR
• rises to ≥1.5-fold from baseline in the preceding 7 days.

Urine output:

• <0.5 ml/kg/h for 6 hours.

Question 3

What is the volume of blood flow through the kidneys?

Answer 3

About 20% of the body’s blood is sent to the kidneys.

SV x HR = 70ml x 60 = 4,200-5,000ml per min.

(almost as much as the brain)

Question 4

What three classifications of renal disease are there?

(and an example of each)

Answer 4

Pre-renal:

• Hypovolemia,
• Cardiac failure.

Renal / Intrinsic:

• Lupus nephritis,
• Acute interstitial nephritis.

Post-renal:

• Papillary necrosis,
• Tumours (prostate),
• Kidney stones.

Question 5

What is pre-renal kidney diease?

Answer 5

Anything related to a decrease in pressure/volume leading to a reduced supply of blood to the kidney.

• therefore, decreased pressure at the glomerulus.
  e. g.
• Low blood volume (e.g., dehydration),
• Low blood pressure,
• Heart failure (leading to cardiorenal syndrome),
• Liver cirrhosis,
• Local changes to the blood vessels supplying the kidney.

Question 6

What is renal / intrinsic kidney diease?

Answer 6

Anything affecting the:

• Glomerulus / blood vessels / tubules / kidney cells (interstitium).

E.g.

• Glomerulonephritis,
• Acute tubular necrosis (ATN),
• Acute interstitial nephritis (AIN).
• Drug Toxicity.
• Other causes of intrinsic AKI are rhabdomyolysis and tumor lysis syndrome.
• Certain medication classes such as calcineurin inhibitors (e.g., tacrolimus) can also directly damage the tubular cells of the kidney.

Question 7

What is post-renal kidney diease?

Answer 7

Urine not flowing leading to a back pressure on the kidney tubular structures.

E.g.

• Benign prostatic hyperplasia,
• Kidney stones,
• Obstructed urinary catheter,
• Bladder stones,
• Cancer:
  
  • Bladder, ureters, or prostate.

Question 8

What are some main functions of the kidney?

(five are listed)

Answer 8

Clearance of waste products.

Excretion of electrolytes.

Control of water balance.

Regulation of acid-base balance.

Production of hormones.

Question 9

What will happen if you dont produce any/small amounts of ultrafiltrate?

When does this become a life-threatening complication?

Answer 9

Will result in fluid accumation = oedema.

Becomes life-threatening in the lungs:

• Pulmonary oedema.
  
  • (results in hypoxia)

Question 10

What happens to the ECG during hyperkalaemia?

Answer 10

First sign = peaked t-waves.

As K+ increases, the QRS complex gets broader.

Question 11

What is the emergency treatment for hyperkalaemia?

Answer 11

Insulin dextrose.

Question 12

What is uraemia?

Answer 12

The retention of metabolic waste products:

(sulphate, urea, ammonia, creatinine, phosphate, e.t.c.)

Question 13

What are some pathologies caused by uremia?

Answer 13

Pericarditis,

• Retention of metabolic waste products:
  
  • (sulphate, urea, ammonia, creatinine, phosphate etc

Pleurisy,

Encephalopathy.

Question 14

How does uremia cause pericarditis?

Answer 14

Pericarditis is the retention of metabolic waste products:

• (sulphate, urea, ammonia, creatinine, phosphate etc)

The metabolic waste inflames the pericardium.

• Chest pain but no dysfunction of the heart.

Fluid (and blood) can build up and fill the pericardium

• (haemorrhagic) Pericardial effusion.

Is life-threatening.

Question 15

What are the three stages of AKI?

(classified by KDIGO)

Answer 15

Question 16

What is the first, immediate, step in managing a patient who you have identified has AKI?

Answer 16

Exclude a life-threatening complication;

If it is: correct / treat emergently.

Question 17

Generally, how would you treat _{(immediate management)} AKI caused by:

Hypovolaemia?

Low BP?

Drug-induced?

Sepsis-induced?

Answer 17

Hypovolaemia:

• Fluids.

Low BP:

• Fluids and drugs.

Drug-induced:

• Stop drugs.

Sepsis-induced:

• Treat sepsis.

Question 18

What kind of drugs should you avoid in AKI?

Answer 18

Avoid nephrotoxic drugs.

Question 19

When should patients be given RRT?

Answer 19

When they have a life-threatening complication of AKI:

• Life threatening pulmonary oedema.
• Severe metabolic acidosis.
• Severe hyperkalaemia, especially if ECG changes present.
• Uraemic pericarditis.
• Uraemic encephalopathy.