20.4: Thrombolytics
By the end of this section, you should be able to:
- 20.4.1 Identify the characteristics of the thrombolytic drugs used to treat thrombus formation.
- 20.4.2 Explain the indications, actions, adverse reactions, and interactions of the thrombolytic drugs used to treat thrombus formation.
- 20.4.3 Describe nursing implications of thrombolytic drugs used to treat thrombus formation.
- 20.4.4 Explain the client education related to thrombolytic drugs used to treat thrombus formation.
Thrombolytics to Break Down an Existing Clot
Anticoagulant and antiplatelet medications work in the clotting cascade to prevent clotting in clients without a thromboembolism or to prevent worsening of an existing clot while the body breaks the clot down over time. Conversely, thrombolytics work to quickly break down an existing clot, which is often needed when the clot is blocking blood flow to a major organ. They work by facilitating conversion of plasminogen to plasmin. Plasmin then initiates fibrinolysis, or fibrin clot breakdown.
Safety Alert
Alteplase
Alteplase is frequently referred to as tPA as an abbreviation for tissue plasminogen activator (which refers to the mechanism of action). However, this can be confused with TNK, an abbreviation sometimes used for tenecteplase, or TPN, the abbreviation for total parenteral nutrition, which has led to medication errors and/or medication delays in circumstances where timing is crucial. The nurse should avoid using tPA as an abbreviation for alteplase.
See this Institute for Safe Medication Practices (ISMP) report for more information on potential medication errors associated with alteplase .
Alteplase
Alteplase is an intravenous thrombolytic drug that is approved to treat acute ischemic stroke, acute myocardial infarction, and pulmonary embolism. Alteplase works quickly upon administration, and the half-life is less than 5 minutes. It requires reconstitution prior to administration, which is somewhat complicated and further explained in the product labeling and manufacturer website . Because of the high risk of bleeding, the risks and benefits must be carefully weighed prior to administration. Alteplase has many contraindications, which are listed in Table 20.8. These contraindications are clinical characteristics or disease states that put the client at an unacceptable risk for bleeding complications. For example, severe uncontrolled hypertension increases the risk of intracranial hemorrhage in clients receiving alteplase. Thus, alteplase should be avoided in those clients. Prior to administering alteplase, the nurse should confirm that the client does not have any contraindications to therapy.
In small doses, alteplase can also be used as an agent to restore function of central venous access devices that are unable to draw blood due to thrombus formation. For this use, it is known by the brand name Cathflo Activase.
Tenecteplase
Tenecteplase is approved for treatment of ST-elevation myocardial infarction (STEMI). The most common adverse effects are bleeding and hypersensitivity. Like alteplase, it has many contraindications that would put the client at an unacceptable risk of bleeding: active internal bleeding, history of cerebrovascular accident, intracranial or intraspinal surgery or trauma within 2 months, intracranial neoplasm, arteriovenous malformation, or aneurysm, known bleeding diathesis, and severe uncontrolled hypertension. Although not FDA approved, off-label use of tenecteplase for acute ischemic stroke is gaining popularity and is listed as an option in the guidelines for treatment of acute ischemic stroke (Powers, 2019). Some of the practical advantages of tenecteplase as compared to alteplase are that it is quicker to prepare, does not require a dedicated intravenous line or pump, and can be administered as an IV bolus.
Table 20.7 lists common thrombolytics and typical routes and dosing for adult clients. Protocols are usually site specific and should be utilized accordingly.
| Drug | Routes and Dosage Ranges |
|---|---|
|
Alteplase
( Activase , Cathflo Activase ) |
Acute ischemic stroke:
0.9 mg/kg (not to exceed 90 mg total) IV over 60 minutes, with 10% of the dose administered as an initial bolus over 1 minute.
Acute myocardial infarction: Weight-based dosing up to maximum of 100 mg. Acute massive pulmonary embolism: 100 mg IV infusion over 2 hours. Restoration of function of central venous access devices (Cathflo Activase): Instill 2 mg/2 mL into the dysfunctional catheter. |
|
Tenecteplase
( TNKase ) |
Acute ST elevation myocardial infarction:
Weight-based dosing; 30–50 mg administered as a single IV bolus based on the client’s weight.
Acute-ischemic stroke (off-label)*: 0.25 mg/kg IV; maximum dose: 25 mg. |
Adverse Effects and Contraindications
The main adverse effect of thrombolytic therapy is bleeding, which is sometimes severe and can be fatal. This is especially frequent at arterial and venous puncture sites, which leads to nursing implications regarding vascular access described in the next section. Hypersensitivity reactions are also possible. When used to treat coronary thrombus in a client with an acute myocardial infarction, there is an increased risk of dysrhythmias after blood flow is restored. The specific contraindications to thrombolytics are discussed within the content for the specific drugs but are mostly related to bleeding risk.
Table 20.8 is a drug prototype table for thrombolytics featuring alteplase. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.
|
Drug Class
Thrombolytic Mechanism of Action Converts plasminogen to plasmin, which breaks down clot-bound fibrin |
Drug Dosage
Acute ischemic stroke: 0.9 mg/kg (not to exceed 90 mg total) IV over 60 minutes, with 10% of the dose administered as an initial bolus over 1 minute. Acute myocardial infarction: Weight-based dosing up to maximum of 100 mg. Acute massive pulmonary embolism: 100 mg IV infusion over 2 hours. Restoration of function of central venous access devices (Cathflo Activase): Instill 2 mg/2 mL into the dysfunctional catheter. |
|
Indications
Acute ischemic stroke Acute myocardial infarction Acute massive pulmonary embolism Therapeutic Effects Breaks down thrombus to restore blood flow |
Drug Interactions
Anticoagulants Antiplatelets ACE inhibitors Food Interactions No significant interactions |
|
Adverse Effects
Bleeding, including severe bleeding and fatal bleeding |
Contraindications
General: Active internal bleeding Recent intracranial or intraspinal surgery or serious head trauma Intracranial conditions that may increase risks for bleeding Current severe uncontrolled hypertension Acute ischemic stroke: Current intracranial hemorrhage Subarachnoid hemorrhage Acute myocardial infarction or pulmonary embolism: History of recent stroke Caution: Increased risk for bleeding Monitor for hypersensitivity Reembolization risk from lysis of DVT Cholesterol embolism (rare) |
Nursing Implications
The nurse should do the following for clients who are taking thrombolytics:
- Obtain baseline vital signs.
- Avoid intramuscular injections, internal jugular, and subclavian venous punctures during infusion. If an arterial puncture is necessary during infusion, the nurse should use an upper extremity blood vessel that can be compressed and should apply pressure applied for 30 minutes afterward. The nurse should also monitor the puncture site closely.
- Ensure clients remain on bedrest following thrombolytic administration to reduce falls and subsequent bleeding risk.
- Monitor the client for bleeding via a complete blood count and monitoring for other signs/symptoms.
- Notify the provider immediately if signs or symptoms of bleeding occur; treatments such as cryoprecipitate (blood-derived clotting factors) or antifibrinolytic medications (medications that prevent fibrin breakdown, such as aminocaproic acid or tranexamic acid) may be warranted.
- Monitor for hypersensitivity reactions.
- Initiate an additional IV line for clients receiving alteplase because alteplase requires a dedicated IV line.
- Monitor for changes in the client’s condition depending on the indication for use.
- Administer thrombolytic therapy promptly; there are specific time frames that the drug must be administered for full therapeutic effect, depending on the disease state being treated.
- Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.
Client Teaching Guidelines
The client taking a thrombolytic should:
- Recognize the signs/symptoms of bleeding as described under adverse effects. Providers should be notified immediately if any of these signs and symptoms occur.
- Recognize the signs/symptoms of therapeutic failure, depending on the disease state being treated.
- Remain on bedrest after thrombolytic administration to reduce falls and subsequent bleeding risk.
- Follow drug-specific dietary guidelines.
The client taking a thrombolytic should not:
- Discontinue therapy unless following specific instructions from the health care provider.
- Schedule any invasive procedure without direct communication with the health care provider, including but not limited to dental procedures.