Introduction
Indications for CRRT
Acute kidney injury with oligo/anuria (< 0.5 ml/kg/h) |
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Fluid overload > 10% |
Severe electrolyte imbalance refractory to medical treatment |
Metabolic abnormalities (e.g., hyperammonemia refractory to medical treatment) |
Severe metabolic acidosis |
Uremic complications(e.g., encephalopathy, pericardial effusion, pulmonary edema) |
Intoxications (e.g., drugs and toxins) |
Septic shock with need of toxins clearance (e.g., endotoxins, cytokines) |
Need to make room for more fluids for drug therapy and/or nutrition |
Timing of initiation
Key aspects of CRRT delivery
Vascular access
CRRT modality and dose
Technique | Physical principle | Minimum duration (hours) | Advantages | Disadvantages |
---|---|---|---|---|
PD | Diffusion | 24 | • Technically, the simplest modality • Require less infrastructure and lower costs • No need for anticoagulation • Possible in hemodynamically unstable patients | • Slow small molecule and uremic toxin clearance • Less predictable fluid removal • Risk of infections (e.g., peritonitis) • Not possible if recent abdominal surgery • May have impact on respiratory stability |
IHD | Diffusion | 4–6 | • Rapid removal of toxins, electrolytes and fluid overload • Minimal/no need for anticoagulation • Relatively lower cost than the techniques below • Less restrictions on patients mobility | • Not recommended in critically ill hemodynamically unstable patients • Increased risk of hypotension and electrolytes disequilibrium • Require vascular access • Technically expertise required • Clearance rebound |
PIRRT/SLED | Diffusion | 6–12 | • More rapid solutes removal than CRRT, but slower than IHD • More hemodynamically stable than IHD • Technically simpler than the techniques below • Relatively lower cost (e.g., less bags needed) • More restrictions on patients mobility than IHD but less than the techniques below | • Not recommended in critically ill hemodynamically unstable patients • Require vascular access and anticoagulant • Risks of hypotension and disequilibrium • Lower efficiency than other modalities |
CVVH | Convection & ultrafiltration | 24 | • Convection allows highly efficient middle molecule and cytokine removal • Continuous removal of uremic toxins and fluid • Possible use in hemodynamic unstable patients | • Technically complex (e.g., complex circuit and high cost) • Require vascular access and anticoagulant (systemic or regional) • Need patient immobility • Prolonged exposure to membranes • Less efficient for small molecule removal than IHD |
CVVHD | Diffusion & ultrafiltration | 24 | • Continuous removal of uremic toxins and fluid • Possible use in hemodynamic unstable patients • Better removal of small molecules than CVVH | • Technically complex (e.g., complex circuit and high cost) • Require vascular access and anticoagulant (systemic or regional) • Need patient immobility • Prolonged exposure to membranes • Less efficient for small molecule removal than IHD |
CVVHDF | Diffusion, convection & ultrafiltration | 24 | • Convection allows highly efficient middle molecule and cytokine removal • Continuous removal of uremic toxins and fluid • Possible use in hemodynamic unstable patients • Better removal of small molecules than CVVH | • Technically most complex CRRT modality (e.g., complex circuit with frequent bag changes and high cost) • Require vascular access and anticoagulant (systemic or regional) • Need patient immobility • Prolonged exposure to membranes • Less efficient for small molecule removal than IHD |
Characteristic | PD | IHD | CRRT |
---|---|---|---|
Duration | Continuous for 24 h | Intermittent (4–6 h) | Continuous for 24 h |
Technical difficulties | + | + + | + + + |
Influence on hemodynamics | + | + + + | + |
Control of fluid removal | ± | + + | + + + |
Possible catheter issues | Obstruction, leak, peritonitis | Hemorrhage, thrombosis, dislocation | Hemorrhage, thrombosis, dislocation |
Availability | + + + | + + | + |
Anticoagulation | Not necessary | Variably needed | Needed |
Daily solute removal | + | + + + | + + + |
Rapidity of solute clearance | + | + + + | + + |
Easy to use in neonates | + + + | - | + |
Method of anticoagulation
Method | Dosing (D) and monitoring (M) | Advantage | Disadvantage |
---|---|---|---|
Unfractionated heparin | D: 10–20 IU/kg/h | • Easily reversible with protamine • Low costs and widely available • wide experience as anticoagulant | • Risk of patients bleeding • Patients possibly developing heparin induced thrombocytopenia (HIT) • Unpredictable and complex pharmacokinetics resulting in dosing variability |
M: aPTT 45–60 s or 1.5–2 × NR; ACT 180–200 s | |||
Low Molecular Weight Heparin | D: Enoxaparin LD 0.15 mg/kg, MD 0.05 mg/kg/h | • Less risks for HIT • Pharmacokinetics more predictable than unfractionated heparin | • Higher costs than unfractionated heparin • Less effective reversal with protamine |
M: Anti-Xa level (0.3–0.7 UI/mL) | |||
Regional citrate anticoagulation | D: starting dose 3 mmol/La | • Anticoagulation only of the extracorporeal circuit • Lower risks of bleeding • Longer filter life than heparin | • Need for training and strict protocols • Higher risks of citrate complications (electrolytes imbalance, citrate accumulation/toxicity) • Need for high dialytic dose (high volume of pre-filter fluid) • May need caution in patients with severe liver failure and lactic acidosis |
M: extracorporeal iCa 0.25–0.35 mmol/L; intracorporeal iCa 1.1–1.3 mmol/L | |||
Regional heparin and protamine | D: infuse 1 mg protamine post-filter for 100 IU Heparin | • Anticoagulation only of the extracorporeal circuit • Lower risks of bleeding | • Complex metabolism may lead to prolonged anticoagulation • Requires measurement of both circuit and patient APTT • Technically challenging (difficulty in estimating the amount of protamine required to antagonize post-filter heparin) • Possible side effects: hypotension, anaphylaxis, cardiac depression, leukopenia, and thrombocytopenia |
M: circuit aPTT 45–60 s or 1.5–2 × NR; ACT 180–200 | |||
Prostacyclin infusion | D: 2–8 ng/kg/min | • No need for anticoagulation parameter monitoring since inhibits platelets aggregation • Easy to perform | • Possible hemodynamic impact, dose dependent (vasodilation, systemic hypotension, possible reflex tachycardia) • Possible raised intracranial pressure |
M: no monitoring tests | |||
Serine protease inhibitors—nafamostat mesilate, aprotinin | D: Depending on drug | • Lower costs than regional citrate anticoagulation • Alternative to regional citrate anticoagulation if risk of citrate accumulation | • Only few studies available in pediatrics • Need for clotting parameter monitoring |
M: aPTT 45–60 s or 1.5–2 × NR; ACT 180–200 s | |||
Direct thrombin inhibitors—argatroban, bivalirudin | D: Depending on drug | • Lower bleeding risk than unfractionated heparin in other context (e.g., ECMO) • Shorter half-life than heparin (bivalirudin the shortest) • Possible use in patients with HIT | • Only few studies available in pediatrics, evidences from adults • Non-reversible agents available |
M: aPTT 45–60 s or 1.5–2 × NR; ACT 180–200 s |