How would dialysis help a patient with acute kidney injury (AKI)?

How Dialysis Helps in Acute Kidney Injury

Dialysis in AKI serves as life-saving renal replacement therapy that corrects life-threatening metabolic derangements, removes excess fluid, and maintains homeostasis when the kidneys cannot perform these functions. 1

Primary Mechanisms of Benefit

Dialysis addresses the core pathophysiologic consequences of AKI through several critical mechanisms:

Electrolyte Correction

• Removes life-threatening hyperkalemia, particularly when accompanied by ECG changes, which represents an absolute indication for emergent dialysis 1
• Corrects severe dysnatremia (both hypo- and hypernatremia) that is symptomatic or resistant to medical management 1
• Manages hypocalcemia and hyperphosphatemia that commonly complicate AKI 2

Acid-Base Balance Restoration

• Corrects severe metabolic acidosis with impaired respiratory compensation, an absolute indication for emergent intervention 1
• Treats refractory lactic acidemia that fails medical management 1
• Bicarbonate-based dialysate (rather than lactate) should be used, especially in patients with circulatory shock or liver failure 3

Fluid Management

• Removes pulmonary edema unresponsive to diuretics, preventing respiratory failure 1
• Treats severe fluid overload causing respiratory compromise, particularly in anuria or oliguria with progressive volume accumulation 1
• Provides precise fluid balance control that cannot be achieved with diuretics alone 4

Uremic Toxin Removal

• Prevents and treats uremic complications including encephalopathy, pericarditis, and uremic bleeding—all absolute indications for emergent dialysis 1
• Removes accumulated metabolic waste products that the failing kidneys cannot clear 2
• Delivers adequate solute clearance with a Kt/V of 3.9 per week for intermittent therapy or 20-25 mL/kg/h effluent volume for continuous therapy 3

Modality Selection Based on Clinical Context

Continuous Renal Replacement Therapy (CRRT)

CRRT is preferred for hemodynamically unstable patients requiring vasopressor support because it provides gentler fluid removal and better hemodynamic tolerance 3, 1

• Indicated for patients with acute brain injury or increased intracranial pressure, as it provides more stable control without rapid osmotic shifts 3, 1
• Allows for continuous, gradual correction of metabolic derangements over 24 hours rather than intermittent bursts 3
• Reduces inflammatory processes and hypermetabolism compared to intermittent modalities 3
• Delivers effluent volume of 20-25 mL/kg/h to achieve adequate clearance 3, 5

Intermittent Hemodialysis

• Preferred for rapid correction of severe hyperkalemia in hemodynamically stable patients due to faster potassium clearance 1, 6
• More efficient for patients who can tolerate the hemodynamic stress of shorter, more intensive treatments 3
• Requires delivery of Kt/V of 3.9 per week 3

Prolonged Intermittent Kidney Replacement Therapy (PIKRT)

• Combines advantages of both continuous and intermittent modalities with 8-12 hour sessions 3
• Provides better hemodynamic stability than standard intermittent hemodialysis while being more practical than 24-hour CRRT 3
• No clear superiority demonstrated over CRRT for most indications 3

Critical Technical Considerations

Anticoagulation Strategy

• Regional citrate anticoagulation should be considered for CRRT in patients without contraindications 1, 5
• Heparin is recommended for intermittent hemodialysis in patients not at increased bleeding risk 3
• Minimal or no anticoagulation should be used in trauma or bleeding-prone patients 6

Buffer Selection

• Bicarbonate-based solutions are strongly recommended over lactate, particularly in patients with shock (level 1B recommendation) 3
• Bicarbonate is also preferred in liver failure and lactic acidemia 3
• This prevents accumulation of lactate that cannot be metabolized in critically ill patients 5

Vascular Access

• Uncuffed non-tunneled dialysis catheters should be used for initial access in emergent situations 3, 1
• Ultrasound guidance is strongly recommended for catheter insertion 3
• Preferred site selection: right internal jugular vein first, femoral vein second, left internal jugular third, and subclavian vein last 3

Common Pitfalls and How to Avoid Them

Timing Errors

• Do not delay dialysis when absolute indications are present—waiting for "a little more time" with severe hyperkalemia with ECG changes, uremic pericarditis, or refractory pulmonary edema increases mortality 1
• Conversely, prophylactic hemodialysis should not be used to prevent contrast-induced AKI 3

Inadequate Dosing

• Frequent assessment of actual delivered dose is essential, as prescribed dose often differs from delivered dose 3
• Underdosing leads to inadequate solute clearance and persistent uremic complications 2

Electrolyte Overcorrection

• Dialysis can trigger hypokalemia, hypophosphatemia, and metabolic alkalosis if not carefully monitored 2
• Continuous techniques allow more time for gradual correction and maintenance of balance 2

Hemodynamic Instability

• Using intermittent hemodialysis in hemodynamically unstable patients can worsen hypotension and organ perfusion 3
• CRRT provides slower, more controlled fluid removal that prevents hemodynamic collapse 1, 5

Special Clinical Scenarios

Postrenal AKI

• Relief of obstruction is the primary treatment, but dialysis becomes necessary when metabolic complications cannot wait for obstruction relief 6
• After bilateral obstruction relief, massive polyuria may develop requiring careful fluid replacement (80-100% of losses with lactated Ringer's) 6

Trauma-Associated AKI

• Earlier initiation of renal replacement therapy may be associated with improved survival 1
• Crush-related AKI requires earlier and more frequent dialysis due to higher incidence of hyperkalemia and acidosis 1

Rhabdomyolysis

• Progressive AKI with myoglobinuria represents a relative indication for dialysis initiation 1
• More aggressive fluid management and earlier dialysis may prevent progression 7

Monitoring During Dialysis

• Regular assessment of electrolytes, acid-base status, and fluid balance is essential throughout treatment 5
• Pre-dialysis serum creatinine should be monitored weekly in patients requiring ongoing therapy 5
• Residual kidney function should be assessed regularly to determine potential for recovery 5

Recovery and Transition

• Kidney recovery is defined as sustained independence from dialysis for a minimum of 14 days 5, 6
• Consider transitioning from CRRT to intermittent hemodialysis when vasopressor support is discontinued, hemodynamic stability is achieved, and fluid balance can be adequately controlled 5, 6
• Avoiding excessive fluid removal and hypotension during dialysis can prevent re-injury and enhance likelihood of renal recovery 5
• Approximately 10-30% of AKI survivors may still require dialysis after hospital discharge, necessitating close nephrology follow-up 8