What could happen in a Chronic Kidney Disease (CKD) patient undergoing hemodialysis (HD) when the vascular access site suddenly loses bruit and thrills after 46 minutes of treatment?

Sudden Loss of Bruit and Thrill During Hemodialysis: Access Thrombosis

The sudden absence of bruit and thrill during an ongoing hemodialysis session indicates acute access thrombosis, which requires immediate intervention within 24-48 hours to salvage the access and avoid permanent loss. 1, 2

Immediate Clinical Significance

The loss of thrill and bruit during active dialysis represents acute thrombotic occlusion of the vascular access, which is the most common and serious flow-related complication. 1 This is a dialysis emergency because:

• Thrombosis is the leading cause of access loss and occurs when underlying stenosis (typically at the venous anastomosis) progresses to complete occlusion, often precipitated by intradialytic hypotension or reduced blood flow. 1
• Episodes of hypotension during HD are contributory factors to thrombosis in the presence of underlying stenosis. 1
• The risk of delay is progressive thrombus growth, making interventional or surgical procedures more difficult and reducing long-term success rates. 1
• Prolonged thrombus contact with the vessel wall increases endothelial damage, favoring future stenosis and recurrent thrombosis. 1

What Happens Next: Immediate Assessment Algorithm

Step 1: Confirm Thrombosis (Perform Immediately)

• Palpate the entire access for thrill - complete absence confirms thrombosis. 1, 2
• Auscultate with stethoscope - absence of the normal low-pitch continuous diastolic and systolic bruit confirms occlusion. 1
• Check for pulse - presence of pulse without thrill suggests complete thrombosis. 1
• Assess hand perfusion - examine for pallor, coldness, cyanosis, or pain to rule out concurrent steal syndrome. 2

Step 2: Manage the Current Dialysis Session

• Continue the current dialysis session if possible with close monitoring, as the access may still allow some flow through collaterals, though this is uncommon with complete thrombosis. 2
• Assess adequacy of current treatment - if blood flow rates have dropped below 300 mL/min or cannot be maintained, the session may need early termination. 1, 3
• Monitor for complications - watch for signs of distal ischemia (hand pain, pallor, coldness) which would require immediate vascular surgery consultation. 2

Step 3: Arrange Urgent Intervention (Within 24-48 Hours)

The vascular access should be reopened as soon as possible to resume regular dialysis and avoid resorting to a temporary catheter. 1

Diagnostic and Therapeutic Approach:

• Fluoroscopy fistulography is the reference standard for both diagnosis and simultaneous therapeutic intervention, allowing visualization from arterial anastomosis to the heart. 1, 2
• Endovascular thrombectomy/thrombolysis has 75-94% clinical success when performed promptly. 2
• Surgical thrombectomy is an alternative if endovascular approaches fail or are unavailable. 1

Critical Pitfalls to Avoid

• Do not delay intervention beyond 48 hours - progressive thrombus organization makes salvage increasingly difficult and reduces long-term patency. 1
• Do not dismiss subtle preceding signs - patients often have warning signs in prior sessions including elevated venous pressures, difficulty achieving target blood flow, or changes in thrill quality that were missed. 1
• Do not assume the access is permanently lost - early thrombectomy can restore function in the majority of cases if performed within 24-48 hours. 1, 2
• Do not place a tunneled catheter immediately - attempt access salvage first, as catheter placement increases infection risk and future central vein stenosis. 4

Underlying Cause and Prevention

Thrombosis results primarily from progressive venous outflow stenosis caused by intimal and fibromuscular hyperplasia, typically at the venous anastomosis. 1 The stenosis causes:

• Increased intra-access pressure with decreased blood flow - when access flow drops below 600 mL/min in grafts or 450-500 mL/min in fistulas, thrombosis risk increases dramatically. 1
• Intradialytic hypotension as a precipitating factor - the combination of stenosis and hypotension during this session likely triggered the acute thrombosis. 1, 4

Prevention Strategy for Future:

• Physical examination before every cannulation to detect early warning signs (weak thrill, high-pitched systolic-only bruit, difficulty compressing access). 1
• Monitor for clinical indicators including elevated venous pressures, prolonged bleeding post-dialysis, difficulty achieving prescribed blood flow, or arm swelling. 1
• Intervene on stenosis before thrombosis occurs - stenosis ≥50% with clinical indicators should be treated with angioplasty to prevent thrombosis. 4

Temporary Access Needs

If thrombectomy fails or cannot be performed within 24-48 hours:

• Temporary non-tunneled catheter placement may be necessary for the next dialysis session. 1
• Avoid placing new permanent access until the current access is definitively deemed unsalvageable. 1
• Consider alternative access sites if this access cannot be salvaged - contralateral arm or lower extremity options. 1