What are the evidence‑based indications for initiating renal replacement therapy (dialysis) in a patient with acute kidney injury?

Indications for Initiating Dialysis in Acute Kidney Injury

Initiate renal replacement therapy immediately when life-threatening metabolic derangements exist—specifically severe hyperkalemia with ECG changes, refractory pulmonary edema causing respiratory compromise, severe metabolic acidosis with impaired compensation, or uremic complications (encephalopathy, pericarditis, bleeding)—rather than waiting for arbitrary creatinine or BUN thresholds. 1, 2, 3

Absolute (Emergent) Indications

These conditions require immediate dialysis initiation regardless of creatinine or BUN values:

Hyperkalemia

• Severe hyperkalemia (>6.0 mmol/L) or rapidly rising potassium with ECG changes (peaked T waves, widened QRS, loss of P waves) 2, 3, 4
• Intermittent hemodialysis is preferred over CRRT for rapid potassium correction due to faster clearance 2, 3

Fluid Overload

• Pulmonary edema unresponsive to diuretics causing respiratory compromise 1, 2, 3
• Anuria or severe oliguria with progressive volume overload 3

Acid-Base Disturbances

• Severe metabolic acidosis with impaired respiratory compensation 1, 2, 3
• Note: The Surviving Sepsis Campaign suggests against bicarbonate therapy for pH ≥7.15 in sepsis-induced lactic acidosis, but this does not preclude dialysis for severe acidosis 5

Uremic Complications

• Uremic encephalopathy (altered mental status, asterixis, seizures) 1, 2, 3, 4
• Uremic pericarditis (friction rub, chest pain) 1, 2, 3, 4
• Uremic bleeding (platelet dysfunction) 1, 2, 3

Relative Indications

Consider dialysis initiation for these conditions, particularly when trending toward life-threatening complications:

• Severe progressive hyperphosphatemia (>6 mg/dL), especially in tumor lysis syndrome before overt uremic symptoms develop 2
• Severe symptomatic hypocalcemia in the setting of hyperphosphatemia 2
• Rapidly rising BUN and creatinine with trajectory suggesting imminent complications 2, 6, 7
• Rhabdomyolysis with progressive AKI and myoglobinuria 3

Critical Timing Principle

Do not base the decision to initiate dialysis on absolute creatinine or BUN values alone. 5, 1, 6 The Canadian Society of Nephrology and KDIGO guidelines explicitly state that specific criteria for RRT initiation based on laboratory thresholds cannot be delineated in the absence of life-threatening complications 5. While a BUN of 75 mg/dL has historically been suggested as a threshold, this is based on limited evidence and should not supersede clinical judgment 7.

The trajectory of disease, clinical condition, and presence of modifiable complications are more important than numerical values. 6, 7 Recent evidence suggests that initiating dialysis at earlier AKIN stages without traditional indications does not improve survival and may increase resource utilization 8. The 2017 Surviving Sepsis Campaign explicitly recommends against using RRT in sepsis patients with AKI for creatinine elevation or oliguria alone without other definitive indications 5.

Modality Selection

Continuous Renal Replacement Therapy (CRRT)

CRRT is mandatory for: 1, 2, 3

• Hemodynamically unstable patients requiring vasopressor support 5, 1
• Patients with acute brain injury or increased intracranial pressure 1, 2, 3
• Severe fluid overload unresponsive to diuretics when hemodynamic instability is present 5, 1
• Patients on extracorporeal life support (ECMO/VAD) 1

The KDIGO guidelines (grade 2B) and Surviving Sepsis Campaign support using CRRT to facilitate fluid balance management in hemodynamically unstable patients 5.

Intermittent Hemodialysis (IHD)

IHD is preferred for: 2, 3

• Rapid correction of severe hyperkalemia in hemodynamically stable patients
• Patients who are hemodynamically stable without increased intracranial pressure

The evidence shows no survival difference between CRRT and IHD in hemodynamically stable patients 5, 9.

Technical Implementation

Vascular Access

• First choice: Right internal jugular vein 1, 2
• Use uncuffed non-tunneled dialysis catheter for emergent situations 2, 3

Dialysis Dose

• For intermittent RRT: Deliver Kt/V of 3.9 per week (approximately 1.2-1.4 per session for thrice-weekly treatments) 5, 2
• For CRRT: Deliver effluent volume of 20-25 mL/kg/h 5, 1, 2, 3
• Prescribe higher than target dose to compensate for downtime and interruptions 1

Anticoagulation

• Regional citrate anticoagulation is preferred for CRRT in patients without contraindications (shock liver, severe lactic acidosis) due to lower bleeding risk and longer filter life 5, 2, 3

Fluid Composition

• Use bicarbonate-based replacement fluids rather than lactate-based solutions in patients with shock, liver failure, or lactic acidemia 1, 3

Common Pitfalls to Avoid

1. Waiting for specific BUN or creatinine thresholds while life-threatening complications develop 5, 1, 6
2. Initiating early "preemptive" dialysis without traditional indications, which does not improve mortality and increases resource utilization 5, 8
3. Using intermittent hemodialysis in hemodynamically unstable patients, which can worsen hypotension and organ perfusion 5, 1
4. Excessive fluid removal causing hypotension, which can impede renal recovery 1
5. Assuming renal recovery based on creatinine normalization during dialysis rather than sustained independence from RRT for ≥14 days 1

Special Populations

• Trauma-associated AKI and crush injuries may require earlier initiation and more frequent dialysis due to higher incidence of hyperkalemia and acidosis 3
• Patients with sepsis and AKI should not receive RRT for creatinine elevation or oliguria alone without definitive indications, as early initiation may cause harm (central line infections) without mortality benefit 5