When to initiate dialysis in a patient with acute kidney injury?

When to Initiate Dialysis in Acute Kidney Injury

Dialysis should be initiated emergently when life-threatening metabolic derangements exist, specifically: severe hyperkalemia (>6.0 mmol/L or with ECG changes), refractory pulmonary edema, severe metabolic acidosis with impaired compensation, or uremic complications (encephalopathy, pericarditis, bleeding). 1, 2

Absolute (Emergent) Indications

These conditions require immediate dialysis initiation to prevent mortality:

Electrolyte Emergencies

• Severe hyperkalemia (>6.0 mmol/L) or rapidly rising potassium with ECG changes (peaked T waves, widened QRS, sine-wave pattern) 1, 2
• Persistent hyperkalemia unresponsive to medical management (insulin/glucose, calcium, beta-agonists, sodium bicarbonate) 1, 3
• Severe symptomatic dysnatremia resistant to medical therapy 1

Fluid Overload

• Pulmonary edema unresponsive to diuretics causing respiratory compromise 1, 3
• Severe volume overload with respiratory failure 1, 4
• Anuria or oliguria with progressive fluid accumulation 1

Acid-Base Disturbances

• Severe metabolic acidosis with impaired respiratory compensation 1, 3
• Refractory lactic acidemia despite medical management 1

Uremic Complications

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

Relative Indications

Consider dialysis initiation when these conditions develop:

• Severe progressive hyperphosphatemia (>6 mg/dL) before overt uremic symptoms, particularly in tumor lysis syndrome 5, 2
• Severe symptomatic hypocalcemia (tetany, seizures) in the setting of hyperphosphatemia 5
• Rapidly rising BUN and creatinine with trajectory suggesting imminent life-threatening complications 1, 6
• Rhabdomyolysis with progressive AKI and myoglobinuria 1

Critical Pitfalls to Avoid

Do not wait for BUN to reach arbitrary thresholds (e.g., BUN >100 mg/dL) if life-threatening complications are present—these numerical cutoffs are outdated and not evidence-based for emergent situations 6

Do not routinely treat asymptomatic hypocalcemia that accompanies hyperphosphatemia with calcium supplementation, as this worsens calcium-phosphate precipitation in tissues 2. Only symptomatic hypocalcemia (tetany, seizures) requires cautious calcium gluconate 2

Do not rely solely on serum creatinine in patients with low muscle mass, elderly patients, or those with recent muscle wasting—creatinine may appear "normal" despite severe kidney injury 7

Modality Selection Based on Clinical Context

Intermittent Hemodialysis (IHD)

• Preferred for rapid correction of severe hyperkalemia (clearance 70-100 mL/min) 2
• Most efficient for removing uric acid, urea, potassium, and phosphate 2
• First-line for hemodynamically stable patients requiring urgent solute removal 2

Continuous Renal Replacement Therapy (CRRT)

• Mandatory for hemodynamically unstable patients requiring vasopressor support 5, 1, 2
• Required for patients with acute brain injury or increased intracranial pressure (provides more stable hemodynamics and better ICP control) 1
• Preferred when pulmonary edema is present (allows gentler fluid removal) 5, 1
• Consider for tumor lysis syndrome with continuous metabolite release 5, 2

Special Populations

• Trauma-associated AKI: Earlier RRT initiation may improve survival 1
• Crush-related AKI: Requires earlier and more frequent dialysis due to higher risk of hyperkalemia and acidosis 1
• Tumor lysis syndrome: Frequent (daily) dialysis recommended due to continuous release of purines, potassium, and phosphate 5, 2

Practical Implementation

Vascular access: Use uncuffed non-tunneled dialysis catheter for emergent situations; right internal jugular vein is first choice, followed by femoral vein (avoid in obese patients), then left internal jugular, with subclavian as last resort 5, 1

Dialysis dosing: Deliver Kt/V of at least 1.2 per treatment (3 times weekly for IHD) or effluent volume of 20-25 mL/kg/h for CRRT 5, 1

Anticoagulation: Regional citrate anticoagulation preferred for CRRT in patients without contraindications 5, 1

Dialysate: Use bicarbonate-based (not lactate-based) dialysate, especially in shock, liver failure, or lactic acidemia 1