4.3 Thrombolytic Therapy (tPA/Alteplase/Tenecteplase) Protocols
Key Takeaways
- IV Alteplase (tPA) dosing for ischemic stroke is strictly 0.9 mg/kg, with a maximum absolute dose of 90 mg.
- Alteplase is administered with 10% of the total dose given as an IV bolus over 1 minute, and the remaining 90% infused over exactly 60 minutes.
- Blood pressure must be strictly maintained < 185/110 mmHg prior to thrombolytic initiation, and strictly < 180/105 mmHg for 24 hours post-administration.
- The standard therapeutic window for IV thrombolysis is within 3 hours of last known well (LKW), extended to 4.5 hours for highly specific, selected patient populations.
- Tenecteplase (TNKase) is emerging as a preferred alternative given as a single weight-based IV bolus (typically 0.25 mg/kg, max 25 mg), offering greater fibrin specificity.
Thrombolytic Therapy Protocols
Intravenous thrombolysis remains a fundamental cornerstone in the acute medical management of ischemic stroke. The primary agent historically utilized is Alteplase (recombinant tissue plasminogen activator, or rt-PA), though Tenecteplase (TNKase) is rapidly replacing it as the standard of care in many comprehensive stroke centers. These powerful medications work by converting endogenous plasminogen into plasmin, an enzyme that actively degrades the fibrin matrix of a thrombus, effectively dissolving the clot and restoring cerebral perfusion to the ischemic penumbra.
The Crucial Concept of "Last Known Well"
The administration of thrombolytics is completely dependent on determining the exact time the patient was "Last Known Well" (LKW). This is the precise date and time the patient was last witnessed to be at their neurological baseline. If a patient wakes up with stroke symptoms, the LKW is the time they went to sleep, completely excluding them from standard time-based IV thrombolytic windows.
- Standard Window: Within 3 hours of LKW for most eligible patients.
- Extended Window: Within 3 to 4.5 hours of LKW for highly selected patients (specifically excluding those >80 years old, those with a history of both prior stroke AND diabetes, those taking oral anticoagulants regardless of INR, and those with severe stroke NIHSS >25).
Strict Blood Pressure Parameters
Blood pressure management is the most critical physiological parameter the nurse must aggressively control prior to, during, and after thrombolytic therapy. Elevated blood pressure violently forces blood into the fragile, ischemic, and necrotic tissues of the stroke bed, drastically increasing the risk of severe symptomatic intracerebral hemorrhage (sICH).
- PRE-Thrombolytic Goal: BP MUST be steadily < 185/110 mmHg before the drug can be mixed or initiated. If BP exceeds this, antihypertensives (e.g., IV Labetalol, Nicardipine, or Clevidipine drips) must be administered. If the BP cannot be safely lowered below 185/110 mmHg, the patient is disqualified from receiving thrombolytics.
- POST-Thrombolytic Goal: BP MUST be maintained strictly < 180/105 mmHg for at least 24 hours after the initiation of the infusion. Frequent monitoring is mandatory.
Alteplase (tPA) Dosing and Administration
The dosing and administration protocol for Alteplase is rigid and unforgiving of errors. It requires a precise two-step administration process.
- Dosing Formula: 0.9 mg/kg of actual body weight.
- Maximum Absolute Dose: 90 mg (therefore, any patient weighing >100 kg simply receives the flat 90 mg dose).
Administration Protocol:
- The Bolus: Exactly 10% of the calculated total dose is drawn up and administered as an IV push over precisely 1 minute.
- The Infusion: The remaining 90% of the total calculated dose is administered as a continuous IV infusion over exactly 60 minutes via a dedicated infusion pump.
- The Flush: Because the IV tubing contains residual medication, a 50 mL normal saline flush must be programmed into the pump to run at the exact same rate as the infusion immediately after the medication bag empties, ensuring the patient receives the complete calculated dose.
Example Calculation: A patient weighs 80 kg.
- Total Dose: 80 kg x 0.9 mg/kg = 72 mg total
- Bolus Dose: 10% of 72 mg = 7.2 mg (given over 1 minute)
- Infusion Dose: 90% of 72 mg = 64.8 mg (infused over 60 minutes)
- Note: The nurse must actively "waste" or remove the excess medication from the 100 mg vial before hanging the bag to absolutely prevent accidental overdose.
Tenecteplase (TNKase): The Evolving Standard
Tenecteplase is a genetically modified variant of Alteplase. It features a significantly longer half-life, a substantially higher fibrin specificity, and a higher resistance to plasminogen activator inhibitor-1.
- Administration: The overwhelming advantage of Tenecteplase is its administration profile: it is given as a single, rapid IV bolus over 5 seconds. There is no subsequent 60-minute infusion.
- Dosing: The standard dose for acute ischemic stroke is 0.25 mg/kg, up to a maximum dose of 25 mg.
- This single-bolus approach radically accelerates door-to-needle times and greatly simplifies the logistical transfer of patients to the neuro-angiography suite for mechanical thrombectomy (the "drip and ship" model becomes "bolus and ship").
Nursing Care and Vital Sign Monitoring Parameters
Following the initiation of either Alteplase or Tenecteplase, the patient enters a high-acuity 24-hour observation period where they are at high risk for hemorrhagic transformation and other life-threatening complications.
Neurological and Vital Sign Assessment Frequency:
- Every 15 minutes during the 1-hour Alteplase infusion (or for the first hour after Tenecteplase bolus).
- Every 15 minutes for the 2 hours immediately following the infusion.
- Every 30 minutes for the next 6 hours.
- Every 1 hour for the remaining 16 hours (totaling 24 hours of strict monitoring).
Critical Complications to Monitor For:
- Symptomatic Intracerebral Hemorrhage (sICH): Suspect this immediately if there is a sudden severe headache, acute nausea/vomiting, severe hypertension, or a sudden neurological decline (NIHSS increase of 4+ points). Action: STOP the infusion immediately, stat head CT, check labs (PT, PTT, Fibrinogen), and prepare to administer cryoprecipitate and tranexamic acid (TXA).
- Orolingual Angioedema: A rare but potentially lethal complication, particularly in patients taking ACE inhibitors. It usually presents as asymmetrical swelling of the tongue and lips. Action: STOP the infusion immediately, maintain the airway (intubation may be required), and administer IV antihistamines, corticosteroids, and epinephrine.
- Systemic Bleeding: Monitor IV sites, foley catheters, and gums for excessive oozing. Avoid all invasive procedures (no NG tubes, no arterial lines, no urinary catheters) for 24 hours unless absolutely life-saving.
No antithrombotics (aspirin, clopidogrel) or anticoagulants (heparin) can be administered for a full 24 hours post-thrombolysis, and only after a follow-up head CT confirms the absence of intracranial hemorrhage.
A patient weighing 115 kg is ordered to receive IV Alteplase (tPA) for an acute ischemic stroke. What is the correct total dose, bolus dose, and infusion dose the nurse should prepare?
A patient is receiving an IV Alteplase infusion. Thirty minutes into the 60-minute infusion, the patient complains of a sudden, severe headache, and the nurse notes the patient's blood pressure has spiked to 195/115 mmHg. What is the priority nursing action?
Which of the following represents the correct blood pressure parameters required prior to initiating IV thrombolytic therapy, and the parameters required for the 24 hours following therapy?