What is the maximum blood flow rate (BFR) for hemodialysis via a central venous catheter (CVC)?

Maximum Blood Flow Rate for Hemodialysis Central Venous Catheters

The maximum blood flow rate (BFR) for hemodialysis via a central venous catheter (CVC) should be 300-400 mL/min, with dysfunction defined as failure to maintain a BFR of at least 300 mL/min at a prepump arterial pressure more negative than -250 mmHg. 1

Definition of Adequate Blood Flow for Hemodialysis CVCs

• The American Journal of Kidney Diseases defines adequate blood flow for hemodialysis CVCs as the ability to attain and maintain an extracorporeal blood flow of 300 mL/min or greater at a prepump arterial pressure more negative than -250 mmHg 1
• For high-efficiency dialysis as practiced in the United States, dialyzer-delivered BFRs greater than 300 mL/min are required to achieve the target single-pool Kt/V of 1.2 1
• Newer catheters are capable of achieving rates of 400 mL/min or greater when properly placed 1
• The exception to this standard is for pediatric or smaller adult catheters that are not designed to have flows in excess of 300 mL/min 1

Signs of CVC Dysfunction

• Blood pump flow rates <300 mL/min 1
• Arterial pressure <-250 mmHg 2
• Venous pressure >250 mmHg 2
• Conductance <1.2 (ratio of blood pump flow to absolute value of prepump pressure) 1
• Progressive decrease in URR <65% (or Kt/V <1.2) 1
• Inability to aspirate blood freely (late manifestation) 1
• Frequent pressure alarms not responsive to patient repositioning or catheter flushing 2

Factors Affecting Maximum Blood Flow

• Catheter position: Recirculation in femoral catheters is significantly greater than in internal jugular catheters (13.1% versus 0.4%) 1
• Catheter length: Femoral catheters shorter than 20 cm have significantly greater recirculation (26.3%) than those longer than 20 cm (8.3%) 1
• Catheter design: Newer catheters can achieve higher flow rates of 400 mL/min or greater when properly placed 1
• Thrombotic occlusion: The most common cause of catheter dysfunction, which can significantly reduce blood flow 2
• Catheter malposition or kinking can obstruct flow and reduce maximum achievable BFR 2

Clinical Implications of Inadequate Blood Flow

• A dysfunctional catheter is easier to salvage than a nonfunctional catheter, making early detection and treatment crucial 1
• Low BFRs during hemodialysis extend treatment times and often result in underdialysis due to unrecognized recirculation 1
• A BFR less than 300 mL/min was noted in 15% of treatments with catheters 1
• Catheter dysfunction leads to 17% to 33% of untimely catheter removals 1
• Thrombosis of the catheter occurs in 30% to 40% of patients with catheter access 1

Important Considerations

• Waiting until blood flow decreases to 300 mL/min may be too late to avoid loss of the catheter and unnecessary loss of the access site 1
• Reversal of tubing lines (inversion of inlet and outlet lumens) may temporarily increase urea clearance by increasing blood flow, but it usually results in a BFR less than 300 mL/min and should be avoided 1
• Some research suggests that mean blood flows <300 mL/min are not commonly associated with dialysis inadequacy, and setting a single blood flow cut point of <300 mL/min to define the need for intervention may result in unnecessary interventions 3
• However, the most recent guidelines still maintain that 300 mL/min is the threshold for defining catheter dysfunction 1

Management of Catheter Dysfunction

• Thrombolytics can be used for treating a dysfunctional catheter, using either an intraluminal lytic, intradialytic lock protocol, or an intracatheter thrombolytic infusion or interdialytic lock 1
• If initial treatments fail, a radiographic study using catheter contrast injection should be performed to identify other correctable problems 1
• Regular assessment of dialysis performance is strongly recommended to ensure dialysis adequacy 1