What to do if a dialyzer (artificial kidney) clots twice during the same hemodialysis treatment?

Management of Dialyzer Clotting Twice During Same Hemodialysis Treatment

When a dialyzer clots twice during the same hemodialysis session, terminate the treatment and investigate the underlying cause of inadequate anticoagulation rather than attempting a third dialyzer, as recurrent clotting indicates systemic anticoagulation failure that compromises dialysis adequacy and patient safety. 1

Immediate Actions During the Session

First Priority: Assess Adequacy Impact

• Recognize that dialyzer clotting reduces effective dialyzer surface area and compromises the delivered dose of hemodialysis below prescribed levels. 1
• Document the exact treatment time lost during each dialyzer replacement, as interruptions for dialyzer replacement secondary to clotting reduce actual dialysis time and effective treatment delivery. 1
• Calculate whether the patient can still achieve minimum adequate Kt/V of 1.2 (or URR ≥65%) given the time lost and reduced clearance from partial clotting before complete occlusion. 1

Second Priority: Decision to Continue or Terminate

• If two dialyzers have clotted during the same session, strongly consider terminating the treatment rather than attempting a third dialyzer, as this pattern indicates inadequate systemic anticoagulation that is unlikely to be corrected mid-session. 1
• The rationale is that repeated clotting events suggest either insufficient heparin dosing, heparin resistance, or a hypercoagulable state that requires systematic evaluation rather than repeated attempts. 2, 3
• Document all interruptions meticulously, as failure to account for treatment interruptions due to dialyzer replacement is a common cause of inadequate delivered dialysis dose. 1

Root Cause Investigation (Post-Session)

Anticoagulation Assessment

• Review the heparin protocol used: verify the initial bolus dose (typically 5,000 units IV for full-dose anticoagulation) and maintenance infusion rate (typically 1,000-2,000 units/hour). 4
• For extracorporeal dialysis specifically, a dose of 25-30 units/kg followed by an infusion rate of 1,500-2,000 units/hour is suggested if manufacturer recommendations are unavailable. 4
• Consider whether the patient has risk factors for heparin resistance, including active infection, recent surgery, or inflammatory states. 2

Technical and Equipment Factors

• Check blood flow rate adequacy from the vascular access, as inadequate blood flow is a primary cause of compromised clearance and increased clotting risk. 1
• Verify blood pump calibration, as errors result in actual blood flow rates that are less than assumed and reported, promoting stasis and clotting. 1
• Review extracorporeal pressures during the session, particularly pre-pump arterial pressure for values ≤-200 mmHg, which indicate access flow problems. 1
• Assess for access recirculation using slow flow/stop pump sampling technique if hydraulic compression testing suggests problems. 1

Patient-Specific Factors

• Evaluate for hypercoagulable states: recent thrombotic events, malignancy, antiphospholipid syndrome, or heparin-induced thrombocytopenia. 2, 5
• Recognize that hemodialysis patients are inherently pro-thrombotic, with baseline activation of platelets and the clotting cascade even before dialysis begins. 5
• Review medications: aspirin or coumarin use for fistula thrombosis prevention may paradoxically contribute to clotting through platelet activation. 2

Prevention Strategies for Future Sessions

Anticoagulation Modification

• For patients with recurrent clotting, increase heparin dosing: consider a higher initial bolus (up to 10,000 units) and increased maintenance infusion (up to 2,000 units/hour for standard patients). 4
• Alternative strategies for high-risk clotting patients include regional heparin anticoagulation or minimal heparinization protocols. 2
• For patients actively bleeding or at extreme bleeding risk, consider heparin-free hemodialysis, peritoneal dialysis, or regional anticoagulation with citrate. 2

Dialyzer and Circuit Optimization

• Ensure mandatory preprocessing of all new dialyzers before first patient use to remove manufacturing residuals that can promote clotting. 6
• Measure total cell volume (TCV) before first use to establish baseline dialyzer function and account for variability among dialyzers. 1, 6
• During reprocessing, check TCV after each use; dialyzers with TCV <80% of original measured value should not be reused, as fiber loss from clotting reduces clearance. 1

Blood Flow and Access Management

• Optimize blood flow rates to the maximum tolerated by the vascular access (typically 350-450 mL/min for adequate clearance). 1
• Address any access dysfunction promptly, as inadequate access flow is a primary driver of both inadequate dialysis and circuit clotting. 1

Common Pitfalls to Avoid

• Do not assume that absence of visible red clots at session end means adequate anticoagulation occurred, as subclinical fiber clotting can reduce clearance without obvious macroscopic thrombus. 1, 7
• Avoid relying solely on pre-/post-dialyzer pressure difference (ΔP) monitoring to detect clotting, as urea clearance may not change significantly until minutes before complete circuit occlusion. 7
• Do not continue attempting multiple dialyzer replacements in the same session without addressing the underlying anticoagulation failure, as this wastes resources and delays definitive treatment. 1
• Recognize that continuous monitoring of ΔP during intermittent hemodialysis does not significantly help unmask inefficient sessions, unlike in continuous renal replacement therapy. 7

Documentation Requirements

• Record exact times of dialysis initiation, each interruption for dialyzer replacement, and treatment termination to calculate true effective treatment time. 1
• Document visual inspection of each clotted dialyzer to characterize the extent and pattern of clotting. 1
• Calculate and report the delivered Kt/V or URR for the session, accounting for reduced treatment time and compromised clearance. 1