How to thrombolysis with stk
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streptokinase thrombolysis protocol
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Thrombolysis with Streptokinase (STK)
Streptokinase (STK) is a first-generation fibrinolytic agent derived from beta-hemolytic streptococci. It activates plasminogen indirectly by forming a 1:1 complex with it, which then converts free plasminogen to plasmin - causing systemic fibrinolysis rather than clot-specific lysis.
Mechanism of Action
STK binds to circulating plasminogen, forming an STK-plasminogen activator complex. This complex cleaves other plasminogen molecules to plasmin, which hydrolyzes fibrin and dissolves the clot. Because it is not fibrin-specific, it causes a systemic lytic state (depletes fibrinogen, plasminogen, and clotting factors throughout the circulation).
Indications
| Condition | Role of STK |
|---|---|
| Massive PE (hemodynamic instability) | First-line fibrinolytic when PCI unavailable; approved agent |
| STEMI | Used when PCI cannot be performed within 120 min of first medical contact; within 6-12 hours of symptom onset |
| DVT (iliofemoral, massive) | Careful patient selection required |
| Peripheral arterial occlusion | Catheter-directed or systemic |
Dosing Regimens
For DVT / Pulmonary Embolism (systemic infusion)
Loading dose: 250,000 units IV bolus over 30 minutes Maintenance: 100,000 units/hour by continuous IV infusion for 24 hours (PE) to 72 hours (DVT)
- Tintinalli's Emergency Medicine confirms: "Streptokinase 250,000 units IV bolus, followed by 100,000 units/h continuous IV infusion for 1-3 d"
For STEMI (accelerated regimen)
1.5 million units IV over 60 minutes (via peripheral vein)
- Heparin is generally not co-administered with STK for STEMI (unlike with tPA); adding UFH to STK provides no additional mortality benefit and increases bleeding risk.
- Harrison's notes: "When UFH is added to a regimen of aspirin and a non-fibrin-specific thrombolytic agent such as streptokinase, additional mortality benefit is not achieved."
Contraindications
Absolute:
- Prior hemorrhagic stroke (any time)
- Ischemic stroke within the past 6 months
- CNS neoplasm
- Major trauma, surgery, or head injury within the past 3 weeks
- Active internal bleeding (excluding menses)
- Bleeding diathesis
- Aortic dissection
Relative:
- Systolic BP >180 mmHg or diastolic BP >110 mmHg
- Prior STK exposure within 5 days to 2 years (antibodies develop; repeat dosing is ineffective and increases allergic risk)
- Pregnancy
- Trauma/CPR >10 minutes
- INR >2 (on warfarin)
- Bacterial endocarditis
- Severe renal/hepatic disease
Pre-treatment Steps
- Confirm indication (massive PE with hemodynamic instability, STEMI without PCI access, etc.)
- Screen for all contraindications
- Establish large-bore IV access in a non-compressible site
- Stop heparin if running (check TT/aPTT before restarting anticoagulation post-infusion)
- No arterial punctures in non-compressible sites during and for several hours after infusion
- Pre-medicate with hydrocortisone 100-200 mg IV and an antihistamine (chlorphenamine 10 mg IV) to reduce allergic reactions
During Infusion - Monitoring
- Monitor for hypotension (4-10% incidence with STK; slow infusion rate or give IV fluids if BP drops)
- Monitor for anaphylaxis/allergy (2% incidence)
- Watch for bleeding at venipuncture sites, neurological changes (intracranial bleed)
- Do NOT perform unnecessary arterial punctures or IM injections during therapy
After Infusion
- Wait for TT/aPTT to fall to <80 seconds before restarting anticoagulation (typically 4-6 hours)
- Check fibrinogen level (if <1 g/L, do not restart heparin yet)
- Restart UFH (without bolus) or LMWH, then transition to oral anticoagulation
- Assess reperfusion: resolution of chest pain, normalization of ST segments, reperfusion arrhythmias (STEMI); hemodynamic stabilization, improved oxygenation (PE)
Advantages vs. Disadvantages vs. Alteplase (tPA)
| Feature | Streptokinase | Alteplase (tPA) |
|---|---|---|
| Cost | Low | High |
| Fibrin specificity | Non-specific (systemic lysis) | Fibrin-specific |
| Duration | 60 min (STEMI) or 24-72 h (PE/DVT) | 100 mg over 2 hours (PE) |
| Allergic reactions | ~2% (repeat dosing forbidden) | Minimal |
| Intracranial hemorrhage | ~0.5% (slightly lower than tPA) | ~0.9% |
| Re-use | Cannot repeat within 5 days-2 years | Can repeat |
The Sabiston Textbook notes: "The accelerated intravenous administration (100 mg over 2 hours) of rtPA is preferable to prolonged infusions of streptokinase and urokinase" for PE, reflecting current practice trend toward tPA. However, STK remains a valid and widely used option in resource-limited settings due to its lower cost.
Key Complications
- Major hemorrhage: ~20% risk with systemic use for PE
- Hemorrhagic stroke: 3-5% with systemic PE thrombolysis (all agents)
- Intracranial hemorrhage (STEMI context): ~0.5-0.9% with STK
- Hypotension/allergy: 2-10%; treat with slowing infusion, IV fluids, antihistamines, steroids
Sources: Tintinalli's Emergency Medicine, Ch. 239; Harrison's Principles of Internal Medicine 22E, Ch. 286; Sabiston Textbook of Surgery, Ch. (PE management)
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