Introduction to Streptokinase and Thrombolytic Therapy
Streptokinase is a potent thrombolytic agent used to dissolve dangerous blood clots in vessels. It works by activating plasminogen, which becomes plasmin, an enzyme that breaks down blood clots. This makes it a critical treatment for conditions like heart attack (STEMI), pulmonary embolism, and deep vein thrombosis.
Despite its effectiveness, streptokinase can cause side effects, notably hypotension (low blood pressure). Understanding the mechanisms behind this is crucial for safe administration.
The Mechanisms of Streptokinase-Induced Hypotension
Streptokinase-induced hypotension is complex, involving several pathways, although the primary mechanism is a reduction in total peripheral resistance (TPR).
Reduction in Total Peripheral Resistance (TPR)
A significant decrease in TPR is the main driver of hypotension. This can be attributed to:
- Systemic Fibrinolysis: Streptokinase's non-specific activation of plasminogen leads to widespread breakdown of fibrinogen, reducing blood viscosity and TPR.
- Widespread Vasodilation: The medication can cause widespread widening of blood vessels, directly lowering TPR.
Complement System Activation
Streptokinase's bacterial origin can trigger the complement system.
- Anaphylatoxin Release: This immune response releases anaphylatoxins like C3a, which have been linked to transient hypotension and vasodilation shortly after infusion.
Other Potential Contributors
Less conclusive mechanisms include potential kallikrein system activation and bradycardia.
Clinical Manifestations and Risk Factors
Hypotension with streptokinase is common, often dose-dependent, and more likely with rapid infusions.
Typical Presentation
- Onset and Duration: The blood pressure drop is typically rapid, occurring within 15-30 minutes, and usually transient, lasting only a few minutes.
- Severity: While often mild, severe or persistent hypotension can occur, especially in patients with existing heart conditions.
Key Risk Factors
Factors increasing the risk include:
- Rate of Infusion: Faster rates are linked to greater and more rapid blood pressure drops.
- Patient History: Hypertension and early administration after chest pain are associated with higher incidence.
Management and Clinical Considerations
Managing hypotension is crucial during streptokinase administration. Monitoring is essential.
Standard Management Protocol
- Infusion Adjustment: Slowing or stopping the infusion is a primary step.
- Positioning and Fluids: Trendelenburg position and IV fluid boluses help increase blood pressure.
- Vasopressors: In rare, severe cases, vasopressors may be needed.
Comparison with other Thrombolytics
Newer agents like alteplase are often preferred due to a better safety profile. Here's a comparison:
| Feature | Streptokinase | Alteplase (tPA) |
|---|---|---|
| Antigenicity | High | Low |
| Repeat Use | Not recommended soon after initial use | Can be re-administered |
| Hypotension | More common | Less common |
| Cerebral Hemorrhage | Lower incidence | Higher incidence |
| Fibrin Specificity | Non-specific | Fibrin-specific |
| Cost | Generally more cost-effective | More expensive |
Conclusion
Streptokinase can cause hypotension, primarily through reduced total peripheral resistance and complement activation. This effect is usually transient and managed by adjusting the infusion, positioning, and fluids. While newer agents like alteplase have largely replaced streptokinase in many settings, streptokinase remains valuable in certain situations. Understanding its potential for hypotension is vital for safe use.
