What causes high venous pressure in a Hemodialysis (HD) catheter?

Causes of High Venous Pressure in Hemodialysis Catheters

The most common cause of high venous pressure (>250 mmHg) in a hemodialysis catheter is thrombotic occlusion, which can occur as intraluminal thrombus, catheter tip thrombus, fibrin sheath formation, or fibrin tail development. 1

Primary Causes of High Venous Pressure

Thrombotic Complications

• Intraluminal thrombus - partial or complete occlusion within the lumen of the catheter 1
• Catheter tip thrombus - especially in catheters with side holes, where thrombus may act like a "ball valve" 1
• Fibrin sheath (fibrin sleeve) - fibrin adheres to external surface of catheter with thrombus trapped between sheath and catheter tip 1
• Fibrin tail (fibrin flap) - fibrin adheres to catheter end, creating a "ball valve" effect 1

Mechanical Issues

• Catheter malposition - improper tip location affected by patient position 1
• Kinking of the catheter - causing obstruction to flow 1
• Catheter damage - to external or internal portions 1
• Compression of the catheter between anatomical structures (pinch-off syndrome) 1

Other Causes

• Central venous stenosis - narrowing of the central veins can increase resistance to outflow 2
• Improper catheter length - catheters that are too short or improperly positioned 1
• Loss of anticoagulant lock solution - allowing blood to enter the catheter and form clots 1

Diagnostic Indicators of Catheter Dysfunction

• Venous pressure >250 mmHg is a clear sign of catheter dysfunction 1
• Blood pump flow rates <300 mL/min 1
• Arterial pressure <–250 mm Hg 1
• 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 (a late manifestation) 1
• Frequent pressure alarms not responsive to patient repositioning or catheter flushing 1

Assessment and Management Algorithm

For New Catheters (<2 weeks old):

1. Check for mechanical issues:

   • Evaluate for kinks in the catheter 1
   • Assess if Trendelenburg position is needed to achieve adequate flow (indicates improper placement) 1
   • Check for catheter malposition using imaging if suspected 1

2. If mechanical issues are ruled out:

   • Try patient repositioning and catheter flushing 1
   • Consider line reversal if flow is not restored (though this may increase recirculation) 1

For Older Catheters (>2 weeks old):

1. Suspect thrombotic occlusion as the primary cause 1

2. Implement thrombolytic therapy:

   • Use intraluminal interdialytic thrombolytic lock protocol between dialysis treatments 1
   • Consider tissue plasminogen activator (tPA) for clots 1

3. If thrombolytic therapy fails:

   • Refer for radiographic evaluation to diagnose the specific cause 1
   • Consider catheter exchange over a guidewire if appropriate 1

Prevention Strategies

• Ensure proper catheter placement initially with tip positioned in the mid-right atrium 1
• Use appropriate anticoagulant locking solutions between dialysis sessions 1
• Avoid using the catheter for purposes other than dialysis (blood draws, contrast media) 1
• Implement proper catheter care protocols to prevent damage to external portions 1
• Monitor catheter performance regularly to detect early signs of dysfunction 1

Important Considerations

• Early detection and treatment of catheter dysfunction is crucial as a dysfunctional catheter is easier to salvage than a nonfunctional one 1
• Catheter dysfunction leads to 17-33% of untimely catheter removals 1
• Thrombosis occurs in 30-40% of patients with catheter access 1
• Inadequate blood flow can result in underdialysis and negatively impact patient outcomes 1
• Venous pressure monitoring may be less effective for detecting needle dislodgement in arteriovenous fistulas compared to grafts due to lower baseline pressures 3