AKI

Question 1

Define AKI

Answer 1

50% or more rise in serum creatinine from baseline within last 7 days
Increase in serum creatinine by 26.5mmol/L or more within 48 hours
Urine output < 0.5ml/kg/hour for more than 6 hours

Question 2

What is normal serum creatinine?

Answer 2

Normal serum creatinine is 55-120umol/L

Question 3

How can AKI severity be defined?

Answer 3

1
1.5-2 fold increase from baseline OR increase in serum creatinine of 26mmol/L in 48 hours
Less than 0.5ml/kg/hour urine for >6 hours

2
Increased Cr 2-2.9x baseline
Less than 0.5ml/kg/hour urine for >12hours

3
3 fold increase in serum Cr or serum creatinine > 354mmol/L
< 0.3ml/kg/hour for 24hours or no urine for 12 hours

Question 4

What are the causes of AKI?

Answer 4

Pre-renal:
Sepsis
Dehydration
Haemorrhage
Cardiac failure
Liver failure
Intraoperative damage to renal arteries

Intra-renal
Nephrotoxins such as NSAIDs, ACEi, ARBs, ABXs (aminoglysides - gentamicin), chemotherapy, IV contrast
Parenchymal disease such as glomerulonephritis, acute tubulointerstitial nephritis, rhabdomyolysis, haemolytic uraemia syndrome, multiple myeloma

Post-renal:
Ureteric:
retroperitoneal fibrosis
Bilateral renal stones
Tumours mural/extramural
Bladder:
Acute urinary retention
Blocked catheter
Urethral:
Prostatic enlargement (BPH/malignanacy)
Renal stones

Question 5

What are pre-renal causes of AKI?

Answer 5

Sepsis
Dehydration
Haemorrhage
Cardiac failure
Liver failure
Intraoperative damage to renal arteries

Question 6

What are intra-renal causes of AKI

Answer 6

Nephrotoxins such as NSAIDs, ACEi, ARBs, ABXs (aminoglycosides), chemotherapy, IV contrast
Parenchymal disease such as glomerulonephritis, acute tubulointerstitial nephritis, rhabdomyolysis, haemolytic uraemia syndrome, multiple myeloma

Question 7

What are post-renal causes of AKI

Answer 7

Ureteric:
retroperitoneal fibrosis
Bilateral renal stones
Tumours mural/extramural
Bladder:
Acute urinary retention
Blocked catheter
Urethral:
Prostatic enlargement (BPH/malignanacy)
Renal stones

Question 8

What investigations are required in AKI?

Answer 8

Assess fluid status, BP
Bladder scan for evidence of retention
USS KUB for obstructive cause
Review drug chart for nephrotoxins causing/confounding
Urine dip for causes
Initial bloods (FBC< U&E, CRP, LFT, Ca)

Question 9

How can pre-renal and intrinsic causes of AKI be differentiated?

Answer 9

Urine dip
Urine specific gravity and osmolarity values will be higher in pre-renal causes while Na excretion will be lower due to kidney actively conserving Na and water in pre-renal cases
Golmerulonephritis will show high levels of blood and protein

Question 10

How is AKI managed?

Answer 10

Assess hydration status, look for signs of dehydration
If suspected pre-renal AKI give fluid bolus (250-500ml) over 15 mins and reassess fluid status , monitoring urine output. Give repeat boluses until the patient is fluid repleted and prescribe maintenance fluids

Monitor urine output and consider cauterisation. Daily weight monitoring for fluid overloaded patients

Regular blood tests U&E to monitor progress of serum Creatinine

In those that do not respond to fluid therapy - consider intrinsic/post-renal causes

Alter prescription of drugs that affect/affected by kidneys

Question 11

What are signs of dehydration?

Answer 11

Dry mucous membranes, increased cap refill, reduced skin turgor, tachycardia or in severe cases hypotension

Question 12

What drugs should you stop in AKI?

Answer 12

ACEi/ARBs
NSAIDs
Aminoglycoside abs
Potassium sparing diuretics (increased risk of hyperkalaemia)

Question 13

What drugs should you alter/reduce?

Answer 13

Metformin - risk of lactic acidosis
Diuretics (in case of vascular fluid depletion
LMWH