What is the initial dialysis recommendation for a patient with acute kidney injury (AKI)?

Initial Dialysis Recommendation for Acute Kidney Injury

For hemodynamically stable patients with AKI requiring dialysis, initiate intermittent hemodialysis (IHD) 3 times per week with sessions lasting 3-4 hours; for hemodynamically unstable patients requiring vasopressors, initiate continuous renal replacement therapy (CRRT) with an effluent dose of 20-25 mL/kg/hour. 1, 2

Modality Selection Based on Hemodynamic Status

Hemodynamically Stable Patients:

• Start with intermittent hemodialysis as the standard modality 1
• Schedule treatments 3 times per week, each lasting 3-4 hours 1
• IHD provides faster correction of severe hyperkalemia compared to CRRT 2
• Target a delivered Kt/V of at least 1.2 per treatment (total weekly Kt/V of 3.9) 1, 2

Hemodynamically Unstable Patients:

• Use CRRT rather than intermittent hemodialysis for patients requiring vasopressor support 1, 3
• CRRT provides better hemodynamic stability, slower solute shifts, and better tolerance of fluid removal 1
• Preferred modalities include continuous venovenous hemodiafiltration (CVVHDF) or continuous venovenous hemofiltration (CVVH) 2, 3
• No clear survival advantage has been demonstrated for CRRT over prolonged intermittent kidney replacement therapy (PIKRT) 1

Technical Parameters for Intermittent Hemodialysis

Blood and Dialysate Flow:

• Set blood flow rate at 300-400 mL/min 2
• Set dialysate flow rate at 500-800 mL/min 2

Dialysate Composition:

• Use bicarbonate-based dialysate rather than lactate-based solutions 1, 2
• For severe hyperkalemia, use potassium bath of 0-1 mEq/L; for maintenance use 2 mEq/L 2
• Use calcium bath of 2.5 mEq/L 2

Ultrafiltration Rate:

• Limit ultrafiltration to <13 mL/kg/hour to avoid intradialytic hypotension and further renal injury 2

Technical Parameters for CRRT

Dosing:

• Deliver effluent volume of 20-25 mL/kg/hour for all CRRT modalities 1, 2, 3
• This dose is based on high-quality evidence from the RENAL and ATN trials showing no benefit from higher doses 1

Replacement Fluid:

• Use bicarbonate-based replacement fluids, particularly in patients with shock, liver failure, or lactic acidemia 1, 2, 3

Anticoagulation:

• Use regional citrate anticoagulation for CRRT in patients without contraindications 1, 2
• For patients with contraindications to citrate, use unfractionated or low-molecular-weight heparin 1

Vascular Access

Catheter Type and Placement:

• Use an uncuffed non-tunneled dialysis catheter of appropriate length and gauge 1, 2
• First choice site: right internal jugular vein 1, 2
• Second choice: femoral vein (though inferior in patients with increased body mass) 1
• Third choice: left internal jugular vein 1, 2
• Last choice: subclavian vein (avoid due to stenosis risk) 1, 2
• Always use ultrasound guidance for catheter insertion 1, 2

Special Indications for CRRT Over IHD

Absolute Indications for CRRT:

• Acute brain injury or increased intracranial pressure (CRRT causes less ICP fluctuation than IHD) 1, 3
• Severe fluid overload unresponsive to diuretics 3
• Patients on extracorporeal life support (ECMO) 1, 3

Monitoring During Dialysis

Essential Monitoring:

• Check vital signs hourly and assess for hypotension 2
• Monitor electrolytes and acid-base status every 2-4 hours initially 2
• Measure pre- and post-dialysis weights 2
• Monitor urine output if any residual kidney function remains 2

Transitioning Between Modalities

When to Transition from CRRT to IHD:

• Consider transition when vasopressor support has been discontinued 1, 3
• Hemodynamic stability has been achieved 3
• Intracranial hypertension has resolved 1
• Positive fluid balance can be controlled by intermittent hemodialysis 1

Common Pitfalls to Avoid

Critical Errors:

• Do not use lactate-based dialysate in patients with shock or lactic acidosis—this worsens metabolic acidosis 1, 4
• Avoid subclavian vein access as first choice due to high risk of stenosis with large-bore catheters 1
• Do not prescribe excessive ultrafiltration rates (>13 mL/kg/hour) as this causes intradialytic hypotension and worsens kidney injury 2
• Recognize that prescribed dose often falls short of delivered dose—monitor actual delivered Kt/V 1

Evidence Nuances:

• While older observational data suggested CRRT might improve survival, more recent high-quality evidence shows no mortality benefit of CRRT over IHD 1, 5, 6
• A 2022 secondary analysis of AKIKI and IDEAL-ICU trials found CRRT as first modality was associated with worse 60-day survival compared to IHD (weighted HR 1.26), particularly in less severely ill patients 5
• The choice between CRRT and IHD should be based on hemodynamic status, not on assumptions about survival benefit 1