RENAL FAILURE IN ICU

Jo-Ann Vosloo

Department Critical Care

SBAH

DEFINITION: RIFLE criteria

Criteria for initiation of RRT

Modes of RRT (options)

• CRRT = continuous renal replacement therapy

SCUF : Ultra-filtration

CVVH : Convection

HV-CVVH(HF) : High volume convection

CVVHD : Diffusion & Ultrafiltration

CVVHDF : Convection, Diffusion, Ultra-filtration

• SLEDD

• IHD

• PD

• MPS = membrane plasma separation (plasmaphoresis, plasma exchange) : Convection, exchange

• HP = hemoperfusion (charcoal filter paracetamol poisoning, snake bite): Adsorption

Which mode of RRT is the best?

• Aspects that should be taken into consideration before the choice is made:

- Haemodynamic side-effects

- Ability to control fluid status

- Biocompatibility

- Risk of infection

- Uremic control

- Avoidance of cerebral oedema

- Ability to allow full nutritional support

- Ability to control acidosis

- Absence of specific side-effects

- Cost

CRRT

CRRT

Indication: Modes CRRT

Mode

• SCUF: (Slow continuous ultra-filtrate)

• CVVH/HV-CVVH:

Continuous venovenous

haemofiltration ± high volume

(Use convection flow)

AV1000 filter

CVVH remove fluid and small, medium +

large molecules.

CVVH-HV Rather for metabolic acidosis. For

cold, trauma patient with acidosis.

Indications

Diuretic unresponsive fluid retention (pulmonary oedema)

ARF with shock, MOF, unconciuosness,

hemodynamic instability, severe cardiac insufficiency

Diuretic resistant fluid retension Removal of toxic metabolic products Life-threatening electrolyte imbalance e.g.

hyperkalaemia Correction of acid-base balance e.g. metabolic

acidosis Elimination of mediators in MOF, sepsis, ARDS,

pancreatitis, trauma

Indication: Modes CRRT

Mode

• CVVHDF

Continuous venovenous haemodiafiltration

(Convection, diffusion, Ultrafiltration)

Filter: AV1000

• CVVHD Continuous venovenous haemodialysis

(Diffusion and Ultra-filtration)

Filter: HF80S/F40-60S/AV dialyser

Indications ARF with shock, MOF, unconsciousness, hemodynamic

instability, severe cardiac insufficiency

Diuretic resistant fluid retention

Removal of toxic metabolic products

Life-threatening electrolyte imbalance e.g. hyperkalaemia

Correction of acid-base balance e.g. metabolic acidosis

Elimination of mediators in MOF, sepsis, ARDS, pancreatitis, trauma (less effective than CVVH with identical volume)

Renal insufficiency in ICU patients

Removal of life-threatening electrolytes e.g. hypernatremia

Correction of acid-base imbalance

Indication: Modes CRRT

Mode

• Membrane Plasma Separation

(MPS)

Use a plasma filter (PSu2 or 1)

Exchange 60% of estimated plasma

volume

• Hemoperfusion (HP)

Indication Removal of pathogenic proteins

- Malaria

- TTP

- Hemolytic uremia

- Gillian Barre

- Removal of antibodies post-transplant

Use FFP, Ringers and 20% Albumin combination

to do exchange

Removal of toxic substances, also protein- bound substances by adsorption

Charcoal filter

For snake bites, paracetamol and other poisoning

CRRT Current dose rate (dialysate or substrate): 30ml/h/kg) = 2,5l/h for 70kg person

Blood flow rate: ±150ml/h or acc. to UFR/BPR ratio

• Advantages: No matter what technique is used, the following outcomes are predictable:

1. Continuous control of fluid status

2. Hemodynamic stability

3. Control of acid-base status

4. Ability to provide adequate protein rich nutrition , while achieving uraemic

control

5. Control of electrolyte balance, including PO4= and Ca++

6. Prevention of swings of intracerebral water 7. Minimal risk of infection 8. Biocompatibility

• Disadvantages:

1. Needs the presence of specifically trained nurses

2. Higher cost

3. Issues with continuous circuit anti-coagulation and the potential risk of bleeding

4. Cannot disconnect Pt >1 hour to go for e.g. CT scan must change extra-corporeal circuit and

reprime the lines

CRRT and circuit anti-coagulation

CCRT and circuit anticoagulation

• Full heparinisation:

Pulmonary embolism, Myocardial infarction

• Heparin induced thrombocytopenia:

Heparinoids or Prostacycline

• LMWH:

Dose must be adjusted for renal failure patients

Intermittend Hemodialysis (IHD)

• High dialysate flows: 300-400ml/h

• Treatment period: 3-4 hours every second day

• Implications:

- Fluid has to be removed over very short period hypotension

(repeated hypotensive episodes may lead to delayed renal recovery)

- Solute removal is episodic

(inferior acid-base control)

(limited fluid and uremic control limitations on nutritional support)

- Rapid solute shifts increases brain water content ↑ intracranial pressure

- Membrane biocompatibility: Standard low-flux dialysis membranes is made of Cuprophane activates several inflammatory

pathways further renal damage delayed recovery and ?↑ mortality.

SLEDD

• Limitations of IHD has led to the development of Sustained low efficiency daily dialysis

• Use IHD machine

• Over 8-12 hours

• Qd = 300ml/h

• Qb = 150ml/h

Peritoneal dialysis

• Now uncommonly used in developed countries for adult ARF in ICU

• Still used in children greater relative surface area

alternatives too expensive or not available.

• Glucose rich dialysate is used

• Machines available that can deliver and remove dialysate at a higher flow rate.

• Shortcomings:

- Sometimes inadequate solute clearance

- High risk of peritonitis

- Unpredictable hyperglycaemia

- Fluid leaks

- Protein loss

- Interference with diaphragm function

Drug prescription during dialysis

Conclusion

• Textbook of Critical Care (Vincent)