AKI

Question 1

How is AKI diagnosed?

Answer 1

1) Rise in creatinine >26micromol / L in 48hrs
2) Rise in creatinine >1.5 x baseline (best figure in last 3/12)
3) Urine output 6hr consecutively

Question 2

What is the KDIGO staging for AKI?

Answer 2

Based on serum creatinine and urine output.
3 stages
Creatinine:
1) Rise in creatinine >26micromol / L in 48hrs OR rise in creatinine >1.5 x baseline
2) Increase 2-2.9 x baseline
3) Increased 3 x baseline OR >354micromol / L OR commenced on renal replacement therapy regardless of stage

Urine:
1) 6hr consecutively
2) 12hr
3 24hr or anuria for 12h

Question 3

What are the risk factors for developing an AKI?

Answer 3

• Age - >75yr
• CKD
• Peripheral vascular disease
• Cardiac failure
• Chronic liver failure
• Diabetes
• Drugs (esp newly started)
• Sepsis
• Poor fluid intake / increased losses
• History of urinary symptoms

Question 4

What are the causes of AKI

Answer 4

Pre, renal and post.

Pre- renal (40-70%):
1) Due to renal hypoperfusion: any cause including hypovolaemia, sepsis), renal artery stenosis +/- ACE-i

Renal (10-50%):
1) Tubular - acute tubular necrosis (ATN) - commonest cause of AKI, often the result of pre-renal damage or nephrotoxins such as drugs (aminoglycosides), radiological contrast, and myoglobinuria in rhabdomyalosis.
Also crystal damage (ethelyne glycol poisoning, uric acid), myeloma, increased calcium.
2) Glomerular - autoimmune such as SLE, HSP, drugs, infections, primary glomerulonephritides
3) Interstitial - Drugs, infiltration with lymphoma, infection, tumour lysis syndrome following chemotherapy
4) Vascular - vasculitis, malignant HTN, thrombus or cholesterol emboli from angiography, HUS/TTH, large vessel occlusion e.g. dissection or thrombus

Post-renal (10-25%):
Caused by urinary tract obstruction
1) Lunminal - stones, clots, sloughed papillae
2) Mural - malignancy (e.g. ureteric, bladder prostate), BPH, strictures
3) Extrinsic compression - Malignancy, retroperitoneal fibrosis

Question 5

How is AKI managed?

Answer 5

1) General measures
2) Treat underlying cause
3) Manage complications
4) Renal replacement therapy

Question 6

What are the general measures in the initial management of AKI?

Answer 6

1) Assess volume status:
- too low = low BP, low urine output, tachycardia, non-visible JVP, poor skin turgor
- too high = raised BP, raised JVP, lung crepitations, peripheral oedema, gallop rhythm (S3)

2) Aim for euvolaemia - titrate carefully, measure I/O, avoid potassium containing fluid unless hypokalemic
3) Stop nephrotoxic drugs - NSAIDs, ACE-is, Gentamicin, amphotericin. Stop metformin if creatinine high (risk of lactic acidosis). Check and adjust does of really excreted drugs.

4) Monitoring - need ITU/HDU transfer?
- Check BP, pulse, JVP and urine output hourly
- Daily U+Es
- Daily fluid balance chart with weights

5) Nutrition - aim for normal calorie intake (more if catabolism) and protein 0.5g/kg/24hr. Low threshold nor NG tube and parenteral feeding.

Question 7

How do you go about treating the underlying cause of AKI?

Answer 7

1) Pre-renal: Correct fluid levels, treat sepsis, consider transfer to ITU for inotropic support
2) Renal: Refer early to nephrologists tubulointerstitial, glomerular pathology or indications for dialysis
3) Post-renal: Catheterise, CTKUB, if sign of obstruction / hydronephrosis urologist for stenting

Question 8

How do you manage the complications of an AKI?

Answer 8

1) Hyperkalaemia:
- correct fluids (normal saline)
- 10ml 10% IV calcium gluconate through big vein over 2 mins. Repeat as necessary until ECG improves (cardioprotective)
- IV Insulin + glucose
- Salbutamol nebulizers (high doses needed 10-20mg), tachycardia can limit use
- If venous bicarbonate blow, IV sodium bicarbonate (50ml 8.4%)

2) Pulmonary oedema:
- Sit patient up and administer high flow O2
- Venous vasodilation e.g. IV diamorphine 2.5mg + antiemetic e.g. cyclizine
- Furosemide 80-250mg IV or IVI
- If no response urgent haemodyalisis / haemofiltration
- Consider CPAP
- Consider IV nitrates

3) Uraemia:
- Symptomatic management
- May require dialysis e.g. encephalopathy, pericarditis

4) Acidaemia:
- May require dialysis
- Consider sodium bicarbonate PO or IV

Question 9

When to consider RRT?

Answer 9

Haemodialysis vs. haemofiltration

Dialysis if patient stable, filtration if ITU

Question 10

What is the prognosis of AKI?

Answer 10

Depends on the early recognition and intervention.

Mortality can be high: Burns 80%, Trauma/Surgery 60%, Medical illness 30%, Obstetric/poisoning 10%