Can a proper diuretic challenge be performed on a patient with oliguria (reduced urine production) while on Continuous Renal Replacement Therapy (CRRT)?

From the Guidelines

A diuretic challenge should not be performed while a patient is on continuous renal replacement therapy (CRRT) for oliguria, as it may be redundant and potentially harmful, and instead, native kidney recovery can be assessed by temporarily pausing CRRT and administering a furosemide challenge or monitoring urine output during scheduled CRRT breaks. The use of diuretics during CRRT is not recommended, as stated in the KDIGO guideline, which suggests not using diuretics to enhance kidney function recovery or reduce the need for RRT 1. CRRT is already managing fluid removal in these critically ill patients with acute kidney injury who are not producing adequate urine, and adding diuretics would not provide additional benefits.

The physiological rationale is that CRRT artificially replaces kidney function, making it difficult to interpret the kidney's response to diuretics while simultaneously receiving extracorporeal support. Recovery of native kidney function is better assessed by measuring spontaneous urine output or response to diuretics during planned intervals off CRRT, always ensuring the patient remains hemodynamically stable during this assessment. A study by Uchino et al. 1 found that urine output was a less reliable predictor of successful discontinuation of RRT when diuretics were given, which further supports the idea that diuretic challenges should not be performed during CRRT.

Some key points to consider when assessing native kidney recovery in patients on CRRT include:

• Temporarily pausing CRRT (if clinically stable) to administer a furosemide challenge (typically 1-2 mg/kg IV) to evaluate residual kidney function
• Monitoring urine output during scheduled CRRT breaks
• Ensuring the patient remains hemodynamically stable during the assessment of native kidney recovery
• Avoiding the use of diuretics during CRRT, as recommended by the KDIGO guideline 1.

Overall, the management of fluid removal and assessment of native kidney recovery in patients on CRRT should be individualized and based on the patient's clinical status and response to treatment.

From the Research

Diuretic Challenge in Oliguric Patients on CRRT

• The use of diuretics in critically ill patients with acute kidney injury (AKI) is a common practice, with loop diuretics being the most popular choice 2.
• However, the efficacy of diuretics in patients on continuous renal replacement therapy (CRRT) is not well established.
• A study on the furosemide stress test (FST) found that it can be used to predict the timing of CRRT initiation in critically ill patients with AKI 3.
• The FST involves administering a dose of furosemide and measuring the urinary output after 2 hours. A urinary output of more than 200 ml is considered a responsive test, while a output of less than 200 ml is considered non-responsive.
• The study found that FST non-responders were more likely to require CRRT than FST responders, suggesting that the test can be used to identify patients who may benefit from CRRT 3.

CRRT in Oliguric Patients

• CRRT is commonly used in intensive care unit (ICU) settings to manage patients with severe AKI, fluid overload, and hemodynamic instability 4.
• The goal of CRRT is to optimize solute control, acid-base balance, and volume status in critically ill patients 4.
• A study on the benefits of initiating CRRT after brain death in organ donors with oligoanuric AKI found that it can increase the number of organs transplanted per donor 5.
• Another study provided a case-based review of common scenarios and interventions encountered during CRRT delivery, including initial prescription, CRRT dosing, and adjustments related to severe hyponatremia management 6.

Diuretic Resistance and Combination Therapy

• Diuretic resistance can be addressed by optimizing loop diuretic dose and using combination therapy with other agents, such as thiazides or thiazide-like diuretics or carbonic anhydrase inhibitors 2.
• The use of combination therapy can help to overcome diuretic resistance and improve urinary output in patients with AKI 2.
• However, the use of diuretics in patients on CRRT requires careful consideration of the patient's volume status, electrolyte balance, and acid-base status 2.