2. Acute Renal Failure

Question 1

What are the different Indications for RRT

Answer 1

1. Renal Triggers
2. Clearance
3. Systemic Pathology

Question 2

1. Renal Triggers

Answer 2

1. Renal triggers
   - Oliguria / anuria
   - Severe fluid overload
   - Hyperkalaemia
   - Met Acidosis
   - Clin symptomatic Uraemia

Question 3

Clearance

Answer 3

2. Clearance
   - Poison / Overdose (Salicylates)
   - Temperature mx (MH)

Question 4

3. Systemic pathology

Answer 4

Non renal fluid overload

?multi organ dysfunction

Question 5

Modes of renal support

Answer 5

1. Continuous vs Intermittent
2. Source of Pressure Gradient
3. Process of Solute Removal
4. Dose Of RRT

Question 6

1. Continuous Vs Intermittent

Answer 6

Meta Analysis shows no difference in renal or overall outcome

Continuous default for most

Question 7

2. Source of pressure gradient

Answer 7

AV or VV

VV require roller pump to generate pressure gradient

Question 8

3. Process of Solute removal

Answer 8

a HF - CVV HF

b HD CVVHD

C Combo

Question 9

CVV HF

Answer 9

Clearance is via convection

Rate of solute removal is determined by
blood flow
TMP grad
Membrane Coefficient (size / permeability)

Filtrate removal is balance by adding solution to maintain volume

• *hydrostatic pressure gradient drives water across the membrane; **solvent drag carries low weight solutes
• • resulting fluid is the ultrafiltrate

Question 10

HD CVVHD

Answer 10

Diffusion down a conc gradient created b dialysate
across selectively permeable membrane

CVV w/ Low permeability membrane
-clearance diffusion limited to small molecule

No fluid is added to filtrate after

** blood / dialysate flow in opposite direction = counter current flow

Question 11

Combination CVVHDF

Answer 11

CVV with high permeability membrane
counter current dialysate

Solute removal via diffusion and convection
Replacement required to maintain volume

** filtration component exceeds that required for pure fluid removal so solvent drag occurs

** dialysis removes small molecules > 500 Da (urea / Cr / electrolytes / Lithium)

** filtration removes middle 500-5000 Da molecules (large drugs like Vanc) and large >5000 Da molecules (cytokines / complement)

Question 12

Dose of RRT

Answer 12

20-25mL/kg suggested by research to be adequate

High rate clearance - no benefit +/- risk

** 25-35 ml / kg / hour

** higher rates can be used when anticipated downtime ie surgery or for pure nocturnal CRRT leaving patient free during the day (same dose over 24 hours etc)

** higher rates = disequilibrium syn / greater nursing burden

** Ronco’s theory of cytokine removal using CRRT in sepsis - no evidence to support but “cytosorb” cannisters sometimes attached to circuits in paeds sepsis

Question 13

Complications of RRT

Answer 13

Access Cannula

Filter

Anticoagulation

Question 14

Access Cannula

Answer 14

• Haemorrhage
• Infection
• Distal limb vascular occlusion

** migration / thrombosis / embolisation / arrhythmias / pneumothorax / stenosis / death

Question 15

Filter

Answer 15

Hypovolaemia
Overload
Anaemia

Electrolyte abnormalities
Disequilibrium syndrome

Air Embolism

Hypothermia

Haemolysis

Thrombosis

Anaphylactoid rxn (ace inhib & an69 membrane)

Question 16

Anticoagulation

Answer 16

Haemorrhage

Thrombocytopaenia
-including HITS