How should dialysis orders be prescribed for a patient with acute kidney injury, including indications, modality selection (continuous renal replacement therapy, intermittent hemodialysis, or sustained low‑efficiency dialysis) and detailed prescription parameters such as blood flow rate, dialysate flow rate, ultrafiltration goals, anticoagulation, and target laboratory values?

Prescribing Dialysis Orders in Acute Kidney Injury

Initiate renal replacement therapy (RRT) emergently when life-threatening complications exist—specifically severe hyperkalemia with ECG changes, pulmonary edema unresponsive to diuretics, severe metabolic acidosis, uremic complications (encephalopathy, pericarditis, bleeding), or severe fluid overload causing respiratory compromise. 1, 2, 3

Absolute Indications for Emergent Dialysis

Do not wait for arbitrary BUN or creatinine thresholds alone when life-threatening complications are present 1, 4:

• Severe hyperkalemia with ECG changes (peaked T waves, widened QRS, loss of P waves) 1, 2, 3
• Pulmonary edema refractory to diuretic therapy with respiratory compromise 1, 2, 3
• Severe metabolic acidosis with impaired respiratory compensation 2, 3
• Uremic complications: encephalopathy, pericarditis, or uremic bleeding 1, 2, 3
• Severe fluid overload causing respiratory compromise, especially with anuria or oliguria 2, 3

Modality Selection Algorithm

For Hemodynamically Unstable Patients (on vasopressors):

Use continuous renal replacement therapy (CRRT) rather than intermittent hemodialysis 1, 3. CRRT is specifically indicated for:

• Patients requiring vasopressor support 3
• Acute brain injury or increased intracranial pressure 3
• Patients on extracorporeal life support (ECMO/ECCO2R) 1, 3
• Severe fluid overload unresponsive to diuretics 3

For Hemodynamically Stable Patients:

Use intermittent hemodialysis for rapid correction of severe hyperkalemia due to faster potassium clearance 1, 2, 3

CRRT Prescription Parameters

Effluent Dose:

• Deliver 20-25 mL/kg/h effluent volume for all CRRT modalities 1, 2, 3
• Prescribe higher than target dose because delivered dose is typically lower than prescribed due to downtime and interruptions 3

Replacement Fluid Selection:

• Use bicarbonate-based replacement fluids rather than lactate-based solutions, especially in shock, liver failure, or lactic acidemia 1, 3
• Lactate-containing solutions should be reserved only for hemodynamically stable patients without liver dysfunction 3

Anticoagulation Strategy:

• First-line: Regional citrate anticoagulation for patients without contraindications (offers longer filter life and lower bleeding risk) 1, 3
• For citrate contraindications: Use unfractionated or low-molecular-weight heparin 1
• For trauma or bleeding-prone patients: Use minimal or no anticoagulation 1, 2

Blood Flow and Ultrafiltration:

• Avoid excessive fluid removal that may cause hypotension and impede renal recovery 3, 5
• Pre-dilution of replacement fluid can enhance ultrafiltration rates and reduce filter clotting 3

Intermittent Hemodialysis Prescription Parameters

Dialysis Dose:

Deliver a Kt/V of 3.9 per week when using intermittent or extended RRT 1, 2

Treatment Frequency:

• Standard: 3 times per week 1
• In hypercatabolic states (e.g., crush injury, rhabdomyolysis): May require daily or even multiple treatments per day to control potassium 1

Technical Parameters:

• Blood flow rate: Typically 250-400 mL/min (adjust based on vascular access and hemodynamic tolerance)
• Dialysate flow rate: Typically 500-800 mL/min
• Treatment duration: 3-4 hours per session to achieve target Kt/V 1

Vascular Access

First choice: Right internal jugular vein 3

• Second choice: Femoral vein (avoid in high BMI patients) 3
• Third choice: Left internal jugular vein 3
• Last resort: Subclavian vein (higher thrombosis/stenosis risk) 3

Use uncuffed non-tunneled dialysis catheter for acute initiation; consider cuffed catheter if prolonged RRT anticipated 3

Monitoring Requirements During RRT

• Electrolytes and acid-base status: Monitor regularly, with particular vigilance for CRRT-induced hypokalemia and hypophosphatemia 3
• Fluid balance: Assess every 6-12 hours in critically ill patients 5
• Hemodynamic parameters: Use dynamic indices like passive leg-raising test or pulse pressure variation 5
• For citrate anticoagulation: Monitor ionized calcium and total calcium/ionized calcium ratio to detect citrate accumulation 3

Target Laboratory Values

• Potassium: Maintain 4.0-5.0 mEq/L 2
• Bicarbonate: Target >18-20 mEq/L 3
• Fluid balance: Avoid cumulative fluid overload >10-15% of body weight (associated with adverse outcomes and delayed renal recovery) 5, 6
• BUN: While not an absolute threshold, BUN >75 mg/dL in asymptomatic patients may indicate need for dialysis 4

Transitioning from CRRT to Intermittent Hemodialysis

Consider transition when all of the following are met 1, 3:

• Vasopressor support has been discontinued 1, 3
• Hemodynamic stability achieved 1, 3
• Intracranial hypertension (if present) has resolved 1, 3
• Fluid balance can be adequately controlled by intermittent hemodialysis 1, 3

Discontinuation Criteria

• Kidney recovery: Sustained independence from RRT for minimum of 14 days 2, 3
• Assessment of residual function: Perform 24-hour urine collection to measure urine volume and creatinine/urea clearance 3
• When RRT no longer aligns with patient's overall care goals 3

Common Pitfalls to Avoid

• Do not base initiation solely on absolute creatinine or BUN values—consider the broader clinical context and trajectory of disease 1, 4
• Do not assume normal creatinine during RRT indicates renal recovery—serum creatinine is artificially reduced by dialysis, not by kidney function improvement 3
• Avoid 0.9% saline for fluid resuscitation—use balanced crystalloids (lactated Ringer's) to prevent metabolic acidosis and hyperchloremia 5, 6
• Do not use hydroxyethyl starches—associated with increased mortality and worsened AKI 5
• Avoid excessive fluid removal—can cause hypotension and delay renal recovery 3, 5

Special Considerations

For Patients on ECMO/ECCO2R:

• CRRT is more appropriate due to hemodynamic instability 1
• Earlier RRT may be required for preventing and managing fluid overload 1
• Heparin administration may depend on patient bleeding risk and circuit setup 1

For Crush Injury/Rhabdomyolysis:

• May require daily or multiple dialysis treatments to control hyperkalemia 1
• Intermittent hemodialysis provides rapid potassium clearance and ability to treat multiple patients per day on same machine 1

Post-Obstructive (Postrenal) AKI:

• Relief of obstruction is primary treatment 2
• After bilateral obstruction relief, monitor for massive polyuria requiring careful fluid and electrolyte replacement 2
• Replace 80-100% of measured losses with lactated Ringer's 2
• Potassium replacement typically requires 1-3 mmol/kg/day during polyuric phase 2, 5