What are the initial management steps for acute kidney injury (AKI) in patients with chronic kidney disease (CKD)?

Diagnosis and Management of Acute Kidney Injury on Chronic Kidney Disease

The initial management of acute kidney injury (AKI) in patients with chronic kidney disease (CKD) should focus on identifying and treating the underlying cause, discontinuing nephrotoxic medications, optimizing hemodynamics, and carefully monitoring for complications. 1

Diagnosis and Assessment

• AKI on CKD represents a continuum where acute injury is superimposed on pre-existing kidney disease, with patients at high risk for kidney disease progression 2
• Persistent AKI is characterized by the continuance of AKI by serum creatinine or urine output criteria beyond 48 hours from onset 2
• For patients with AKI on CKD, reassess the underlying etiology and perform precise measurement of kidney function 1
• Timed urine creatinine clearance is the best available estimate of kidney function for patients with persistent AKI in the steady state, as eGFR equations for CKD are not accurate in this setting 2

Initial Management Steps

1. Medication Management

• Discontinue all nephrotoxic medications immediately, including NSAIDs, aminoglycosides, and iodinated contrast media 1, 2
• Hold diuretics, ACE inhibitors, ARBs, and beta-blockers when AKI is diagnosed to prevent further kidney injury 1, 3
• Review and adjust all medication dosages based on reduced GFR 3
• Be particularly cautious with the "triple whammy" combination of NSAIDs, diuretics, and ACE inhibitors/ARBs, which significantly increases AKI risk 1, 2

2. Fluid and Hemodynamic Management

• Assess volume status through clinical examination and potentially central venous pressure monitoring 3
• For hypovolemic patients, administer intravenous fluids cautiously with close monitoring 3
• For patients with prerenal AKI, optimize hemodynamics with fluid resuscitation and target mean arterial pressure of at least 65 mmHg to ensure adequate renal perfusion 1
• Consider vasopressor therapy if fluid resuscitation fails to restore adequate blood pressure 1
• Monitor for fluid overload, which can worsen outcomes in AKI, using urine output, vital signs, and when indicated, echocardiography 1

3. Monitoring and Laboratory Assessment

• Monitor serum electrolytes, BUN, and creatinine every 4-6 hours initially 3
• Track fluid balance with strict input/output measurements 3
• Measure serum calcium during intermittent infusions every 4-6 hours and during continuous infusion every 1-4 hours if calcium supplementation is required 4
• Monitor for signs of uremic complications, including acidosis and hyperkalemia 3

Specific Considerations for AKI on CKD

• Patients with CKD are at higher risk for developing AKI and have worse outcomes when AKI occurs 2
• The duration of AKD (acute kidney disease, defined as kidney dysfunction lasting 7-90 days) and progression to worsened CKD should prompt clinical review of prescribed medications 2
• For patients with renal impairment, initiate medications at the lowest dose of the recommended range and monitor more frequently 4
• Consider nephrology consultation if the etiology of AKI is unclear or subspecialist care is needed 2

Indications for Renal Replacement Therapy (RRT)

• Individualize timing of RRT based on the overall clinical condition rather than specific creatinine or BUN thresholds 1
• Indications for urgent RRT include severe oliguria unresponsive to fluid resuscitation, severe metabolic derangements, uremic symptoms, and fluid overload 3
• Reassess the need for continued RRT daily 3

Prevention of Recurrent AKI

• Continue nephrotoxin avoidance during the recovery phase of AKD to prevent re-injury 2, 1
• Educate patients to avoid taking NSAIDs or new medications without consulting their healthcare provider 2
• Implement a comprehensive drug stewardship program that includes identification of patients at risk for AKI, review of nephrotoxic medications, and dynamic prescription adjustments 3

Common Pitfalls to Avoid

• Inappropriate continuation of nephrotoxic medications during AKI recovery phase can lead to continued kidney damage 3
• Overly aggressive fluid administration in non-hypovolemic patients can worsen outcomes 3
• Neglecting to adjust medication dosages as kidney function changes during recovery 3
• Delaying RRT when clear indications exist, which increases mortality 3
• Failing to identify and address the underlying cause of AKI, which will lead to continued kidney damage 3