What are the current recommendations for Renal Replacement Therapy (RRT) in critically ill Intensive Care Unit (ICU) patients with Impaired renal function?

Current Concepts of RRT in Critically Ill ICU Patients

Modality Selection Based on Hemodynamic Status

For hemodynamically unstable ICU patients with acute kidney injury, use continuous renal replacement therapy (CRRT) rather than intermittent hemodialysis, and prioritize CRRT for patients with acute brain injury, increased intracranial pressure, or cerebral edema. 1

• CRRT provides superior hemodynamic stability through slower, more gradual fluid and solute shifts compared to intermittent modalities 1
• For hemodynamically stable patients, intermittent hemodialysis and CRRT are complementary therapies with no clear mortality difference; selection should be based on clinical context 1, 2
• Sustained low-efficiency dialysis (SLED) represents a hybrid approach combining features of both modalities, though no clear advantage exists over CRRT in unstable patients 3

CRRT Dosing and Prescription

Deliver an effluent volume of 20-25 mL/kg/hour for CRRT in AKI patients, with frequent assessment of actual delivered dose to adjust the prescription. 1

• The prescribed dose must be documented before each session, with systematic monitoring of delivered versus prescribed dose as a quality indicator 1, 4
• Higher doses than those used in chronic kidney disease are indicated for critically ill patients to avoid undertreatment 5
• Adjust the prescription iteratively to achieve goals of electrolyte balance, acid-base correction, solute control, and fluid management 1

Anticoagulation Strategy

Use regional citrate anticoagulation as first-line for CRRT in patients without contraindications, rather than heparin-based anticoagulation. 1

• For patients without increased bleeding risk or existing anticoagulation, regional citrate is preferred over heparin for CRRT (2B evidence) 1
• In patients with increased bleeding risk, still use regional citrate anticoagulation rather than no anticoagulation during CRRT if no citrate contraindications exist 1
• For intermittent RRT, use unfractionated or low-molecular-weight heparin rather than other anticoagulants 1
• In heparin-induced thrombocytopenia (HIT), immediately stop all heparin and use direct thrombin inhibitors (argatroban) or Factor Xa inhibitors; argatroban is preferred in patients without severe liver failure 1

Dialysate and Replacement Fluid Composition

Use bicarbonate rather than lactate as the buffer in all dialysate and replacement fluids for critically ill patients, particularly those with circulatory shock, liver failure, or lactic acidemia. 1, 6

• Bicarbonate is strongly recommended (1B evidence) for patients with circulatory shock due to impaired lactate metabolism 1
• Bicarbonate is also recommended (2B evidence) for patients with liver failure and/or lactic acidemia to prevent worsening metabolic acidosis 1, 6
• All dialysis fluids must comply with AAMI standards for bacterial and endotoxin contamination 1

Vascular Access and Catheter Management

Insert dialysis catheters using ultrasound guidance via an uncuffed nontunneled catheter, with the right internal jugular vein as first choice. 1

• Vein selection hierarchy: (1) right internal jugular, (2) femoral, (3) left internal jugular, (4) subclavian (last choice, preferably dominant side) 1
• Obtain chest radiograph promptly after internal jugular or subclavian placement before first use 1
• Do not use topical antibiotics at the insertion site or antibiotic locks for infection prevention in nontunneled catheters 1
• Ultrasound guidance is strongly recommended (1A evidence) to reduce complications 1

Membrane Selection

Use dialyzers with biocompatible membranes for both intermittent hemodialysis and CRRT in AKI patients. 1

• Biocompatible membranes reduce inflammatory activation and complement activation compared to cellulose-based membranes 1
• This recommendation applies to all forms of RRT in the ICU setting 1

Special Populations and Considerations

Liver Failure Patients

• CRRT is indicated regardless of kidney injury type in acute liver failure patients with AKI 6
• Regional citrate anticoagulation can be used cautiously but requires intensive monitoring of ionized calcium and total calcium to ionized calcium ratio due to impaired citrate metabolism 6
• If citrate is too risky, consider CRRT without anticoagulation or use SLED 6
• Bicarbonate buffering is mandatory (1B evidence) due to impaired lactate clearance 6

Nutritional Considerations

• Patients on CVVHF require higher protein intake (1.5-1.7 g/kg/day) compared to SLED (1.3-1.5 g/kg/day) due to continuous amino acid losses 3
• Monitor for significant losses of water-soluble vitamins, amino acids (10-15g/day), and electrolytes (phosphate, magnesium) during CRRT 6

Timing of Initiation

Initiate RRT before the development of life-threatening complications in critically ill patients, rather than waiting for conventional thresholds. 1, 7

• Start RRT prior to development of diuretic-unresponsive pulmonary edema, severe hyperkalemia, or uremic complications, as consequences are more severe in critically ill patients 1
• Base decisions on comprehensive clinical evaluation rather than specific BUN or creatinine thresholds 7
• The rate of increase of azotemia is more important than absolute values 7

Common Pitfalls to Avoid

• Undertreatment: Delivering inadequate CRRT dose is associated with worse outcomes; systematically monitor delivered versus prescribed dose 4, 5
• Delayed initiation: Waiting for conventional dialysis thresholds in critically ill patients increases risk of complications 1, 7
• Lactate-buffered solutions in shock/liver failure: This risks worsening lactic acidosis due to impaired metabolism 1, 6
• Subclavian access: Avoid due to thrombosis and stenosis risk, particularly problematic if chronic dialysis becomes necessary 1
• Heparin in bleeding risk: Regional citrate is safer in patients with coagulopathy or increased bleeding risk 1