What is the recommended dosage for direct intra‑fistular injection of streptokinase to treat an arteriovenous fistula thrombus?

Streptokinase Direct Injection into AV Fistula Thrombus Dosage

For direct intra-fistular injection of streptokinase to treat arteriovenous fistula thrombosis, administer 250,000 to 1,500,000 units over 40-90 minutes directly into the thrombus site, with treatment initiated within 6-8 hours of thrombosis onset for optimal results.

Evidence-Based Dosing Regimen

The most specific evidence for direct streptokinase injection into thrombosed AV fistulas comes from clinical experience showing a dose range of 250,000 to 1,500,000 units administered over 40-90 minutes directly to the thrombus site 1. This approach differs fundamentally from systemic thrombolysis protocols used for other indications.

Critical Timing Considerations

• Treat within 6-8 hours of thrombosis for best functional recovery 1
• Beyond this window, success rates decline significantly
• Early intervention is essential to minimize temporary catheter dependence

Administration Technique

The procedure involves:

• Ultrasound-guided direct percutaneous injection using a 20-22 gauge spinal needle 2
• Direct delivery into the thrombus under imaging guidance
• May require plasminogen donors in selected cases 1

Alternative Thrombolytic Agents

While the question specifically asks about streptokinase, it's important to note that urokinase has become the more commonly used agent for AV fistula thrombolysis in contemporary practice 2, 3. The evidence shows:

• Urokinase is frequently used for direct percutaneous thrombolysis with high technical success rates (84-100%) 2, 3
• For comparison, systemic urokinase dosing for other vascular thrombosis is 4,400 U/kg bolus over 10 minutes followed by 4,400 U/kg/hour 4, 5

Important Caveats and Pitfalls

Major Limitation: Rethrombosis Risk

The primary problem following successful thrombolysis is immediate rethrombosis 1. This necessitates:

• Concurrent anticoagulation consideration
• Addressing underlying stenosis if present
• Close monitoring in the immediate post-procedure period

When Thrombolysis Alone Is Insufficient

Many thrombosed fistulas have underlying venous stenosis requiring additional intervention:

• Combine thrombolysis with percutaneous transluminal angioplasty (PTA) when stenosis is present 2, 3
• Technical success rates improve to 88-97% when PTA follows thrombolysis 3
• Ultrasound-guided PTA can dissolve residual thrombi regardless of initial thrombolytic success

Contraindications to Consider

Standard thrombolytic contraindications apply 6:

• Active internal bleeding
• Recent stroke or intracranial pathology
• Uncontrolled severe hypertension (>200/120 mmHg)
• Recent major surgery (<2 weeks)
• Known bleeding diathesis
• Previous streptokinase exposure within 6 months (due to antibody formation and allergic risk) 7, 4

Clinical Decision Algorithm

1. Confirm thrombosis via ultrasound within 6-8 hours of onset
2. Assess for contraindications to thrombolysis
3. Evaluate for underlying stenosis on imaging
4. If no stenosis: Direct percutaneous thrombolysis alone may suffice 2
5. If stenosis present: Plan for thrombolysis followed by angioplasty 2, 3
6. Administer streptokinase: 250,000-1,500,000 units over 40-90 minutes under ultrasound guidance 1
7. Monitor for complications: Bleeding, hematoma formation (occurs in ~13-16% of cases) 2
8. Address residual thrombus: Consider PTA if needed 3

Expected Outcomes

• Thrombolytic success rates: 79.5% for acute thrombosis (<72 hours), declining to 42.9% for subacute thrombosis (72 hours to 7 days) 3
• Overall technical success: 84-100% when combined with adjunctive procedures 2, 3
• Primary patency at 6 months: Approximately 64-68% 3