What is the role of tranexamic acid (TXA) in cardiac anesthesia?

Role of Tranexamic Acid in Cardiac Anesthesia

Tranexamic acid (TXA) is strongly recommended in cardiac anesthesia as an antifibrinolytic agent to reduce perioperative blood loss and transfusion requirements, with a typical dosing regimen of 10-15 mg/kg loading dose followed by 1-5 mg/kg/hour infusion during surgery. 1

Mechanism of Action

Tranexamic acid is a synthetic lysine amino acid derivative that works by:

• Inhibiting fibrinolysis by blocking lysine binding sites on plasminogen
• Preventing plasmin from binding to fibrin, thus preserving and stabilizing fibrin's matrix structure
• Competitively inhibiting plasminogen activation 2

This antifibrinolytic effect helps maintain clot stability during and after cardiac surgery, when fibrinolysis is often activated.

Dosing Recommendations in Cardiac Surgery

Standard Dosing

• Loading dose: 10-15 mg/kg IV after anesthesia induction
• Maintenance: 1-5 mg/kg/hour infusion throughout the operation 1
• Some protocols include adding TXA to the cardiopulmonary bypass pump prime (1-2 mg/kg) 3

Dose Adjustment for Renal Dysfunction

Dose reduction is essential in patients with renal impairment as TXA is primarily eliminated via the kidneys:

Serum Creatinine (mg/dL)	TXA Dosage Adjustment
1.36 to 2.83	10 mg/kg twice daily
2.83 to 5.66	10 mg/kg daily
>5.66	10 mg/kg every 48 hours or 5 mg/kg every 24 hours

2, 4

Clinical Benefits in Cardiac Surgery

1. Reduced Blood Loss:

   • 29-54% reduction in postoperative blood loss compared to placebo 5
   • Significant reduction in mediastinal drainage (649 ± 391 mL with TXA vs. 923 ± 496 mL with placebo) 6

2. Decreased Transfusion Requirements:

   • Reduces the need for allogeneic red blood cell transfusions 5, 6
   • Meta-analyses confirm TXA significantly reduces the number of patients requiring blood transfusions after cardiac surgery with cardiopulmonary bypass 5

3. Mortality Benefit:

   • May contribute to reduced mortality by minimizing bleeding complications 1

Safety Considerations

Contraindications

• Active intravascular clotting
• Subarachnoid hemorrhage
• Hypersensitivity to tranexamic acid 2

Potential Adverse Effects

1. Thromboembolic Risk:

   • Theoretical concern, but clinical trials have not demonstrated increased thrombotic events 1, 7
   • Avoid concomitant use with pro-thrombotic medications 2

2. Seizures:

   • Associated with high doses, particularly in patients over 50 years of age
   • ISMICS recommends maximum total dose of 100 mg/kg 7
   • Consider EEG monitoring in patients with history of seizures 2

3. Other Adverse Effects:

   • Hypersensitivity reactions (including anaphylaxis)
   • Visual disturbances (rare)
   • Dizziness
   • Gastrointestinal disturbances (nausea, vomiting, diarrhea) 2

Special Considerations

1. Timing of Administration:

   • Start administration early, before surgical incision
   • Continue throughout the procedure 1

2. High-Risk Cardiac Procedures:

   • Higher doses may be considered for complex procedures (redo surgery, multiple valve, aortic surgery)
   • Example regimen: 30 mg/kg loading dose, 16 mg/kg/h maintenance, 2 mg/kg in pump prime 3, 4
   • However, higher doses increase seizure risk, so balance risk/benefit

3. Monitoring:

   • Consider thromboelastometry to guide therapy if available 1
   • Discontinue once adequate hemostasis is achieved 1

Implementation in Practice

1. Include TXA in cardiac surgery protocols and checklists
2. Administer before surgical incision
3. Adjust dose based on renal function and bleeding risk
4. Continue infusion throughout surgery
5. Monitor for adverse effects, particularly seizures
6. Consider discontinuation once bleeding is controlled

TXA represents a cost-effective, evidence-based intervention that should be incorporated into standard cardiac anesthesia practice to improve patient outcomes by reducing bleeding complications and transfusion requirements.