Thrombolysis in Emergency Settings

Thrombolysis in Emergency Settings

Thrombolysis in Emergency Settings

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Thrombolysis Basics - Clot Busters 101

  • Goal: Rapidly dissolve intravascular thrombi (clots) to restore perfusion & limit infarct size.
  • Mechanism: Convert inactive Plasminogen $\rightarrow$ active Plasmin.
    • Plasmin degrades fibrin (clot matrix) $\rightarrow$ Fibrin Degradation Products (FDPs).
  • "Clot Busters": Drugs that achieve this enzymatic conversion.
  • Key Principle: "Time is tissue" - earlier administration yields better outcomes. Fibrinolysis pathway diagram

⭐ The primary goal of thrombolysis is the rapid restoration of blood flow to ischemic tissue, thereby minimizing organ damage.

The Drug Arsenal - Clot-Dissolving Crew

These drugs dissolve clots by activating plasminogen to plasmin, which degrades fibrin. Common agents: 📌 SUART (Streptokinase, Urokinase, Alteplase, Reteplase, Tenecteplase).

AgentGenerationFibrin SpecificityHalf-life (IV) & DosingAntigenicityCost
Streptokinase (SK)1stLow (non-specific, systemic lysis)~20-30 min (infusion)High (allergic reactions, prior exposure issues)Lowest
Urokinase (UK)1stLow (non-specific, systemic lysis)~15-20 min (infusion)Low (human source, less than SK)Moderate
Alteplase (t-PA)2ndHigh (clot-specific)~4-6 min (bolus + infusion)Low (recombinant human t-PA)High
Reteplase (r-PA)3rdModerate (better fibrin penetration)~13-16 min (double bolus)Low (recombinant)High
Tenecteplase (TNK-tPA)3rdHigher (most specific, PAI-1 resistant)~20-24 min (single bolus)Low (recombinant)Highest

When to Bust Clots - Emergency Go-Signals

Key indications for thrombolysis:

  • ST-Elevation Myocardial Infarction (STEMI)
    • Symptom onset <12 hours (ideal: <3 hours).
    • ECG: ST ↑ in ≥2 contiguous leads.
  • Acute Ischemic Stroke (AIS)
    • Symptom onset <4.5 hours.
    • Disabling neurological deficit.
    • CT excludes hemorrhage.
    • BP <185/110 mmHg.
  • Massive Pulmonary Embolism (PE)
    • Life-threatening: Sustained hypotension (e.g., SBP <90 mmHg).
    • Or cardiac arrest.

⭐ 'Time is Brain' in acute ischemic stroke and 'Time is Muscle' in STEMI; efficacy of thrombolysis is highly time-dependent.

Thrombolysis Timelines for STEMI and AIS

AIS Thrombolysis Pathway:

Danger Zones & Pitfalls - Clot Busting Risks

Brain CT showing intracranial hemorrhage Key Risks: Bleeding (ICH most feared), allergic reactions, hypotension.

  • Absolute Contraindications (⚠️ High Risk):

    • Any prior Intracranial Hemorrhage (ICH); known cerebral AVM/neoplasm
    • Ischemic stroke within 3 months (unless current acute stroke <4.5h)
    • Suspected aortic dissection
    • Active bleeding (excluding menses); significant bleeding disorder
    • Significant head/facial trauma within 3 months
    • Intracranial/intraspinal surgery within 2 months
    • Severe uncontrolled hypertension (e.g., BP >185/110 mmHg for stroke; >180/110 mmHg for MI/PE if unresponsive)
  • Relative Contraindications (Caution Advised):

    • Age >75 years
    • Current anticoagulant use (e.g., Warfarin with INR >1.7)
    • Recent major surgery (<3 weeks)
    • Recent internal bleeding (2-4 weeks)
    • Pregnancy
    • Severe, chronic, poorly controlled hypertension history

⭐ Intracranial hemorrhage (ICH) is the most feared and life-threatening complication of thrombolytic therapy.

High‑Yield Points - ⚡ Biggest Takeaways

  • Thrombolytics (e.g., Alteplase, Tenecteplase) convert plasminogen to plasmin, dissolving fibrin clots.
  • Key indications: STEMI (within 12h), ischemic stroke (within 3-4.5h), massive PE.
  • Major contraindications: Active bleeding, recent major surgery/trauma, prior ICH, severe uncontrolled HTN.
  • Most feared complication: Intracranial Hemorrhage (ICH); monitor for neurological changes.
  • Streptokinase: Antigenic, risk of hypotension and allergic reactions.
  • Observe for reperfusion signs (e.g., arrhythmias in MI) and bleeding manifestations post-administration.

Practice Questions: Thrombolysis in Emergency Settings

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