Mechanism of Action

Thrombolytics (fibrinolytics) dissolve an existing clot by converting plasminogen to plasmin, which breaks down the fibrin mesh. Unlike anticoagulants such as heparin, which prevent new clot formation, thrombolytics actively lyse a clot already present. This creates a systemic lytic state, so the dominant risk is hemorrhage, especially intracranial.

Thrombolysis: screen, give, watch

Screen for absolute contraindicationsactive bleeding, hemorrhagic stroke, recent surgery <14 days
Confirm within treatment windowbest <3 h; little benefit >12 h from onset
Administer thrombolyticdoor-to-needle 30 min or less
Plasmin lyses fibrin clotrestores coronary flow
Monitor reperfusion + bleedingneuro checks; watch for hemorrhage

Common Medications

alteplasePrototype

tPA

reteplase

tenecteplase

Indications

STEMI when PCI unavailable

or transfer >120 min from first medical contact

treatment within 12 hours of onset

benefit greatest within first 3 hours

Side Effects

minor bleeding or bruising

minor oozing/bruising is expected; major or internal bleeding is a red flag (below)

Contraindications & Interactions

Contraindications

active internal bleeding

history of hemorrhagic stroke

any time, absolute

ischemic stroke within 3 months

intracranial neoplasm

suspected aortic dissection

head or facial trauma within 3 months

major surgery within 14 days

disrupted tissue planes bleed uncontrollably

Interactions

concurrent anticoagulant loading

compounds hemorrhage risk

Administration & Monitoring

two large-bore IVs

type and crossmatch

avoid IM injections

avoid arterial sticks

hold puncture-site pressure 20 minutes

Monitor

baseline coagulation studies

PT/INR, aPTT, platelets, fibrinogen

neuro checks every 15 minutes

for 2 h, then q30 min for 6 h

ST-segment resolution

sign reperfusion achieved

reperfusion dysrhythmias

expected SIGN of successful reperfusion (clot lysis) — not an adverse effect; usually transient

accelerated idioventricular rhythm

classic reperfusion rhythm; monitor, typically self-limited

Patient Teaching

report headache immediately

report any bleeding

gums, urine, stool, IV sites

avoid bumping or injury

remain on bed rest

Report Nowescalate immediately

intracranial hemorrhage Hallmark

sudden severe headache during infusion = ICH until proven otherwise

active internal bleeding

sudden severe headache

stop infusion, notify provider immediately

overt bleeding

occult bleeding

guaiac-positive stool, falling H&H

Clinical Pearl

Thrombolytics bust the clot, but you can't unlyse a brain bleed — screen every contraindication before the needle goes in.

Thrombolytic Therapy