AKI

Question 1

What is acute kidney injury

Answer 1

Rapid reduction in kidney function over a few days
Rapid increased in serum urea and creatinine
Rise in creatinine is >26umol/L in 48hrs or x1.5 baseline in last 7 days
Failure to maintain homeostasis, electrolyte and fluid balance

Question 2

How may AKI present

Answer 2

Dehydration - dry mucous membranes, decreased skin turgor, increased cap refill time, tachycardia, Low bp
Reduced urine output - less kidney function so cannot filter blood as well
Accumulation of urea causing nausea and loss of appetite and confusion
May have abdo pain or back ache - renal stones or urinary retention
Oedema - nephrotic syndrome, not excreting salt and fluid
Can have hypertension due to hypoperfusion so activation of RAAS

Question 3

What are some of the causes of urinary retention

Answer 3

Prostate:

• prostate cancer
• BPH

Iatrogenic
- blocked catheter

Bladder

• overflow incontinence
• bladder tumours

Neurological

• Neurogenic bladder (pelvic splanchnic nerve damage)
• Parkinsons

Drugs

• Anticholinergics e.g. TCAs, Atropine
• spinal anaesthesia
• General anaesthesia

Question 4

How is AKI staged

Answer 4

RIFLE
Stage 1: Risk - x1.5 increase in creatinine GFR decrease in 25% <0.5ml/kg/hr for 6 hrs
Stage 2: Injury - 2x increase in creatinine, gFR decrease by 50%, 0.5ml/kg/hr for 12hrs
Stage 3: Failure - 3x increase in creatinine, GFR decrease by 75%, 0.3ml/kg/hr for 24hrs or no urine output for 12hrs
Loss - complete loss of kidney function for 4 weeks or more
End stage kidney disease - complete loss of kidney function for 3+ months

Question 5

Which drugs should be stopped in AKI

Answer 5

NSAIDs 
Aminoglycosides - gentamycin 
ACE inhibitors 
Angiotensin receptor blockers 
Diuretics - esp K sparing e.g. spironolactone

Question 6

Which drugs should you consider stopping in AKI

Answer 6

Lithium - increases risk of toxicity
Digoxin - toxicity
Metformin - lactic acidosis, also stop if eGFR <30
SC heparin

Question 7

Which drugs are safe to continue in AKI

Answer 7

Paracetamol 
Warfarin 
Statins 
Aspirin (at a cardioprotective dose 75mg OD)
Clopidogrel 
Beta blockers

Question 8

What does tea coloured urine suggest

Answer 8

Myoglobin in the urine due to muscle breakdown 
Can be due to 
- rhabdomyolysis 
- Haemolytic uraemia syndrome 
- multiple myeloma

Question 9

What are the pre renal causes of AKI

Answer 9

hypoperfusion - shock, sepsis, SIRS, haemorrhage

Severe renal artery stenosis or mild/moderate artery stenosis and ACE inhibitor given

Question 10

What are the renal causes of an AKI

Answer 10

Damage within the kidneys
Tubular - ATN –> nephrotoxic drugs, Pre-renal damage and crystal deposits - hypercalcaemia
Glomerular - autoimmune, infection, nephrotoxicity
Interstitial - nephrotoxicity, infection, lymphoma, chemo
Vascular - vasculitis, hypertension, thrombosis/embolism

Question 11

What are the post renal causes of AKI

Answer 11

Urinary tract obstruction
Luminal - renal stones, clots, sloughed papillae
Mural - malignancy, BPH, Strictures
Extrinsic compression - malignancy, retroperitoneal fibrosis
Bladder - blocked catheter, urinary retention

Question 12

How is AKI treated

Answer 12

Treat reversible cause
FLUIDS
- fluid bolus, reassess fluid status after 10-15mins
- repeat fluids until patient is fluid repleted
if patient becomes fluid overloaded whilst still in AKI –> INFORM SENIORS

Monitoring
- Reassess
- Monitor urine output - fluid balance chart, catheter
If fluid overloaded - medical input and daily weight monitoring - may need to start loop diuretics
Monitor BP, HR and daily U+Es

Drug rationalisation

Treat acute complications

• Hyperkalaemia
• Pulmonary oedema
• Acidosis
• Uraemia

Question 13

What are the acute complications of AKI and how are they treated

Answer 13

Hyperkalaemia - 10% calcium gluconate IV over 5 mins followed by 10 units of rapid insulin with 50ml of 50% glucose over 30mins
Pulmonary oedema - loop diuretics, may need dialysis
Acidosis - sodium bicarbonate or dialysis
Uraemia - dialysis

Question 14

Which investigations are done in suspected AKI

Answer 14

Examine patient for fluid status
Bedside: BP, HR, RR, Temp
Urine dip 
- urine specific gravity and osmolality values will be higher in pre renal causes and urine Na will be lower (due to the kidney actively conserving water and Na in pre renal causes)
- blood - stones 
- blood and protein - glomerular disease
- leukocytes - infection
Bladder scan for urinary retention 
Bloods 
- FBC
- U+Es
- CRP
- LFTs 
- bone profile - Ca2+

ABG

If no response to initial management ultrasound of kidneys ureters and bladder - evaluate for obstructive causes