Continuous Renal Replacement Therapy (CRRT)

Question 1

What are the indications to initiate CRRT?

Answer 1

1. Severe AKI or ESRF with either:
   A. Refractory metabolic acidosis
   B. Hyperkalaemia
   C. Uraemic organ involvement (pericarditis, encephalopathy, neuropathy, myopathy)
   D. Fluid overload
2. Coagulopathy +/- requiring large amounts of blood products (such as in acute liver failure)
   - High effluent CRRT
3. Hyperammonaemia or inborn errors of metabolism
4. Intoxication (salicylates, etc)
5. Decompensated liver failure

Question 2

Ideal location of dialysis catheters

Answer 2

1. Internal jugular preferred
   - Longer circuit lifespan
2. In femoral catheter, left preferred to right
   - preserves right for kidney transplant

Question 3

What is the ideal position of catheter tip?

Answer 3

Internal jugular
- Junction of SVC and RA
- Inside RA is acceptable

Femoral
- Inferior vena cava

Question 4

What are the implications if dialysis catheter tip is near to other CVC tip?

Answer 4

Negative pressure of dialysis catheter
–> Medications may be siphoned into dialysis machine

Question 5

What are the catheter locks available?

Answer 5

1. Citrate lock - 4% sodium citrate
   - Specific volume filled to each lumen
2. Heparin lock - 5000 units/mL
   - Specific volume filled to each lumen
3. tPA lock - 1mg/mL
   - 110% of internal volume of each lumen up to maximum 2mL

Question 6

Modalities of CRRT

How does a typical CRRT circuit look like?

Answer 6

Continuous venovenous (CVV) modes:
1. CVVHF (haemofiltration) - convection
2. CVVHD (haemodialysis) - diffusion
3. CVVHDF (haemodiafiltration) - both convention and diffusion

Considerations:
- Convection has better clearance of middle to large molecules and cytokines
- Diffusion has better circuit survival, lower risk of clotting

Question 7

What are the machines available for CRRT?

Answer 7

1. Prismaflex (used in NUH MICU)
   - CVVHF: pre and post-replacement modes
   - CVVHDF: pre-replacement via pre-blood pump; post-replacement via replacement pump
2. Aquarius
   - CVVHF: pre and post-replacement modes
   - CVVHDF: only post-replacement
3. Infomed

Question 8

Dialysers for CRRT

Answer 8

A. Surface area
- Compared to BSA of patient

B. Materials
- M100: basic (FV 152mL)
- Oxiris: heparin-coated, with alleged cytokine removal properties (FV 193mL)