How Dialysis Helps in Acute Kidney Injury
Dialysis in AKI serves as life-saving renal replacement therapy by immediately correcting life-threatening metabolic derangements, removing excess fluid, and providing time for kidney recovery when the native kidneys cannot maintain homeostasis. 1, 2
Primary Mechanisms of Benefit
Correction of Life-Threatening Metabolic Abnormalities
Dialysis directly addresses the absolute indications for emergent intervention:
- Severe hyperkalemia is rapidly corrected, particularly when ECG changes are present, preventing fatal cardiac arrhythmias 2, 3
- Severe metabolic acidosis with impaired respiratory compensation is reversed, restoring physiologic pH 2, 4
- Uremic complications including encephalopathy, pericarditis, and bleeding are treated by removing accumulated toxins 2, 3
- Severe dysnatremia resistant to medical management is corrected in a controlled manner 2
Fluid and Volume Management
- Pulmonary edema unresponsive to diuretics is resolved through precise ultrafiltration 2, 3
- Severe fluid overload causing respiratory compromise is managed, particularly in anuric or oliguric patients with progressive volume accumulation 2
- Continuous modalities allow for gentler, more controlled fluid removal in hemodynamically unstable patients 1, 2
Solute Clearance and Metabolic Control
- Blood urea nitrogen and creatinine levels stabilize after approximately four dialysis sessions, reducing uremic toxicity 5
- Phosphate and other uremic toxins are removed, preventing further complications 4
- The therapy provides time for native kidney recovery while maintaining metabolic homeostasis 3, 6
Modality Selection Based on Clinical Context
Continuous Renal Replacement Therapy (CRRT)
CRRT is the preferred modality for hemodynamically unstable patients requiring vasopressor support, providing superior hemodynamic tolerance compared to intermittent hemodialysis. 1, 2
Key advantages include:
- Better hemodynamic stability with slower, more controlled solute shifts 7
- Reduced risk of intracranial pressure fluctuations in patients with acute brain injury or increased intracranial pressure 1, 2
- Superior fluid removal tolerance allowing precise fluid balance management 7
- Delivery of 20-25 mL/kg/h effluent volume achieves adequate clearance 1, 2
Intermittent Hemodialysis
- Rapid correction of severe hyperkalemia is achieved more efficiently with intermittent hemodialysis in hemodynamically stable patients 2, 8
- Requires Kt/V of 3.9 per week (approximately 1.2 per treatment three times weekly) for adequate dosing 7
- Appropriate for stable patients without increased intracranial pressure or severe hemodynamic compromise 7
Peritoneal Dialysis
- Effective metabolic and fluid control can be achieved in select populations, particularly when extracorporeal options are limited 5
- Fluid removal increases progressively, stabilizing around 2,320 mL after four sessions 5
- Less commonly used in Western ICU settings for adults but remains viable in resource-limited environments 7
Technical Considerations for Optimal Benefit
Buffer Selection
Bicarbonate-based dialysate and replacement fluids should be used rather than lactate-based solutions, especially in patients with shock, liver failure, or lactic acidemia. 7, 1
This is a level 1B recommendation for patients with circulatory shock 7
Anticoagulation Strategy
- Regional citrate anticoagulation should be considered for CRRT in patients without contraindications, providing circuit patency while minimizing systemic bleeding risk 7, 2
- Minimal or no anticoagulation is appropriate for trauma patients or those at high bleeding risk 8
Vascular Access
- Uncuffed non-tunneled dialysis catheters of adequate length should be used for initial access in emergent situations 7
- Right jugular vein is the first choice, followed by femoral vein, then left jugular, with subclavian as last resort 7
Impact on Recovery and Long-Term Outcomes
Kidney Function Recovery
- Kidney recovery is defined as sustained independence from RRT for a minimum of 14 days 1, 8
- Approximately 63% of AKI patients requiring dialysis recover kidney function at discharge 6
- However, nearly 80% of survivors develop chronic kidney disease stage 3 or worse on long-term follow-up 6
Timing of Transition and Discontinuation
Transition from CRRT to intermittent hemodialysis should be considered when vasopressor support is discontinued, hemodynamic stability is achieved, intracranial hypertension has resolved, and fluid balance can be adequately controlled. 7, 1
Critical pitfalls to avoid:
- Excessive fluid removal and hypotension can cause re-injury to recovering kidneys and reduce likelihood of renal recovery 1
- Most patients who recover discontinue dialysis without being weaned from initial prescriptions, suggesting opportunities for earlier liberation 9
- Regular assessment of residual kidney function through pre-dialysis creatinine monitoring is essential 1
Mortality Considerations
- Hospital mortality ranges from 25-30% depending on AKI etiology (medical vs. surgical) 6
- Post-discharge mortality remains significant, with 50% of deaths occurring within the first 156 days after discharge 6
- Factors associated with survival include peak creatinine levels and recovery status at discharge 6
Special Clinical Scenarios
Postrenal AKI
- Relief of obstruction is primary treatment, but dialysis becomes necessary when metabolic or volume complications cannot wait for obstruction relief 8
- After bilateral obstruction relief, massive polyuria may develop requiring careful fluid replacement (80-100% of losses with lactated Ringer's preferred over normal saline) 8
Trauma and Crush Injury
- Earlier initiation and more frequent dialysis may be required due to higher incidence of life-threatening hyperkalemia and acidosis 2
- Trauma-associated AKI may benefit from earlier RRT initiation for improved survival 2