Understanding the Continuous Renal Replacement Therapy Circuit for Acute Renal Failure Support: A Quality Issue in the Intensive Care Unit

Abstract

Delivery of renal replacement therapy is now a core competency of intensive care nursing. The safe and effective delivery of this form of therapy is a quality issue for intensive care, requiring an understanding of the principles underlying therapy and the functioning of machines used. Continuous hemofiltration, first described in 1977, used a system where blood flowed from arterial to venous cannulas through a small-volume, low-resistance, and high-flux filter. Monitoring of these early systems was limited, and without a machine interface, less nursing expertise was required. Current continuous renal replacement therapy machines offer user-friendly interfaces, cassette-style circuits, and comprehensive circuit diagnostics and monitoring. Although these machines conceal complexity behind a user-friendly interface, it remains important that nurses have sufficient knowledge for their use and the ability to compare and contrast circuit setups and functions for optimal and efficient treatment.

Patterns and Mechanisms of Artificial Kidney Failure during Continuous Renal Replacement Therapy

“…Thus, continuous monitoring of multiple circuit pressures may more clearly identify where and how AKF occurs. In this regard, modern CRRT machines can now provide such continuous pressure measurements at different points of the extracorporeal circuit [8] .…”

Continuous Renal Replacement Therapy and Anticoagulation:

“…A well-trained CRRT nurse may be able to identify the source of the alarm and intervene in a timely manner to prevent clotting of blood in the circuit and unnecessary blood loss. 4,8 However, as mentioned earlier, delays in responding or incorrect diagnosis of the cause of the alarm and subsequent clotting may also lead to time without treatment, reducing fluid and solute removal over time and decreasing treatment efficiency. 4 Anticoagulation for CRRT Nonanticoagulant strategies are available for patients who are treated without anticoagulants, including a well-functioning access, high blood flow rates, therapy choice, and quick response to alarms.…”

“…3,8 Insufficient rates can be a primary cause of clotting in the CRRT hemofilter. 4,8,15 Although blood flow does not need to be as fast as in a hemodialysis treatment, blood should move through the circuit at a rate fast enough to prevent clotting. 4,16 Typically, blood flow rates in CRRT are 200 to 300 mL/min.…”

“…4,8 Each time an alarm occurs, the blood pump stops in the CRRT machine and blood flow stops. If the blood pump is not restarted quickly, blood stagnation occurs in the extracorporeal circuit, and the blood begins to clot.…”

“…In addition, the patient's hemodynamic status may become unstable because of the loss of blood, and increased fluid administration may be needed. 4,6,8 Another important consideration when the CRRT circuit is changed more often than usual because of clotting is the potential for central catheter-associated bloodstream infections. This potential increases every time the CRRT blood tubing is disconnected from the catheter, because the dialysis catheters are central blood catheters.…”