AKI

Question 1

What is AKI?

Answer 1

Acute (usually reversible) decreased renal function occurring over hours to days.

Question 2

How is AKI defined using creatinine and urine output?

Answer 2

1) Rise in creatinine of 26micromol/l or greater within 48 hours
2) Rise in creatinine 1.5x baseline or greater within 7 days
3) Urine output <0.5ml/kg/h for >6 consecutive hours

Question 3

What is a stage 1 AKI?

Answer 3

Rise of creatinine of 26 micromol/l or more
OR
1.5-1.99x baseline 
OR
Urine <0.5ml/kg/h for 6 hours

Question 4

What is a stage 2 AKI?

Answer 4

2.0-2.99x baseline
OR
Urine <0.5ml/kg/h for 12 hours

Question 5

What is a stage 3 AKI?

Answer 5

Rise of creatinine to 353.6 micromol/l or more
OR
3.0x baseline
OR
Urine <0.3ml/kg/h for >24 hours or anuria for 12 hours

Question 6

Pre-renal causes of AKI (4 classes)

most common

Answer 6

Decreased vascular volume e.g. haemorrhage, D+V, burns, pancreatitis
Decreased cardiac output e.g. cardiogenic shock, MI
Systemic vasodilation e.g. sepsis, drugs
Renal vasoconstriction e.g. NSAIDs, ACE-i, ARB, hepatorenal syndrome

Question 7

Renal causes of AKI

Answer 7

Intrinsic damage to the glomeruli, renal tubules or interstitium e.g. glomuleronephritis, acute tubular necrcosis, acute interstitial nephritis, rhabdomyolysis, tumour lysis syndrome, vasculitis, thrombosis, toxins and drugs

Question 8

Post-renal causes of AKI

Answer 8

Ureteric stone, malignancy, stricture, clot, or compression from outside e.g. pelvic malignancy, BPH, retro-peritoneal fibrosis

Question 9

Symptoms + signs

Answer 9

May have none
Reduced urine output
Pulmonary and peripheral oedema
Arrhythmias (due to changes in potassium and acid-base balance)
Features of uraemia e.g. pericarditis or encephalopathy (confusion, fatigue, drowsiness)
Dehydration
Nausea and vomiting, diarrhoea

Question 10

Pathological consequences of AKI

Answer 10

Rise in molecules that they kidneys normally excrete
–> hyperkalaemia, uraemia, high creatinine

Oliguria –> fluid overload

Question 11

ECG changes in hyperkalaemia

Answer 11

Tall-tented T waves, small P waves, widened QRS leading to a sinusoidal pattern and asystole

Question 12

How to manage hyperkalaemia? (6)

Answer 12

10-20ml calcium gluconate 10% by slow IV injection
IV soluble insulin (5-10 units) with 50ml glucose 50% given over 5-15 minutes
Salbutamol nebs
Consider sodium bicarbonate infusion
Stop exacerbating drugs
May need haemodialysis

Question 13

How to diagnose AKI?

Answer 13

U+E
Urinalysis
Renal USS if no identifiable cause or at risk of obstruction
Renal biopsy if possibility of vasculitis/AIN/GN

Question 14

How to manage uraemia?

Answer 14

Dialysis

Question 15

How to manage met. acidosis?

Answer 15

Sodium bicarb

Question 16

How to manage AKI

Answer 16

Supportive
Stop meds e.g. NSAIDs, ACE-I, ARB, diuretics
Involve nephrology if severe or cause unknown
Involve urology if obstruction
RRT used if not responding to medical treatment

Question 17

How to do fluid balance assessment

Answer 17

Consider fluid requirements e.g. if trauma, sepsis, burns, D+V, diuretics
Ask about these in the history + symptoms of dehydration/overload

Inspect - age, recent surgery, oedema, colour, drains, catheter, stoma etc.

Obs + fluid balance charts + daily weights + stool chart + drug chart +op note

Hands + arms - inspect, temperature, pulse, cap refill, BP, skin turgor

Face + neck - mucous membranes, sunken eyes, conjunctival pallor, JVP

Chest + abdomen - resp rate, central cap refill, heart sounds, lungs, sacral oedema, ascites

Legs - oedema

Outputs - urine volume + colour, drain quantity, wound losses

Question 18

What are the two main causes of ATN?

Answer 18

Ischaemia and nephrotoxins

Question 19

What are the features of ATN?

Answer 19

raised urea, creatinine, potassium, muddy brown casts in the urine

Question 20

How can pre-renal uraemia be distinguished from ATN?

Answer 20

In pre-renal, the kidneys hold on to sodium to preserve volume so…
Urine sodium low sodium excretion low, urine osmolality high

There are brown granular casts in urine

Good response to fluid challenge in pre-renal

Question 21

When is RTT indicated?

Answer 21

Signs of uraemia e.g. encephalopathy, pericarditis

Not responding to med treatment