How do I administer epinephrine by direct myocardial injection during an emergency department thoracotomy, and how is open‑heart defibrillation performed?

Direct Myocardial Epinephrine and Open-Heart Defibrillation During ED Thoracotomy

During emergency department thoracotomy, administer epinephrine by direct intramyocardial injection at a dose of 1 mg (1 mL of 1:10,000 solution) injected directly into the left ventricular myocardium, and perform open-heart defibrillation using internal paddles at 10-20 joules for the initial shock, increasing to 50 joules if needed.

Direct Intramyocardial Epinephrine Administration

Technique and Dosing

When performing resuscitative thoracotomy with the heart exposed, direct intramyocardial injection provides immediate drug delivery to the myocardium:

• Dose: 1 mg of epinephrine (1 mL of 1:10,000 concentration) 1
• Injection site: Inject directly into the left ventricular myocardium using a small-gauge needle (typically 22-25 gauge)
• Technique: Insert the needle perpendicular to the myocardial surface to a depth of approximately 5-10 mm into the ventricular wall
• Frequency: Repeat every 3-5 minutes as needed during ongoing resuscitation 1, 2

Critical Considerations

The standard cardiac arrest algorithm applies even during open-chest CPR, with epinephrine remaining the cornerstone vasopressor 1, 2. While the 2020 AHA guidelines specify IV/IO dosing of 1 mg every 3-5 minutes for standard ACLS 1, this same dose applies to direct intramyocardial injection during thoracotomy. The intramyocardial route provides more direct myocardial delivery compared to IV administration, though research shows that even with open-chest CPR, pulmonary artery blood flows are only approximately 20% of normal cardiac output 3.

Important pitfall: Do not administer repeated injections at the same site, as vasoconstriction may cause tissue necrosis 4. Rotate injection sites around the left ventricular myocardium with each dose.

Open-Heart Defibrillation

Energy Dosing and Technique

For direct cardiac defibrillation with internal paddles on the exposed heart:

• Initial energy: 10-20 joules
• Subsequent shocks: Increase to 30-50 joules if initial attempts fail
• Maximum: Generally not to exceed 50 joules for internal defibrillation

Paddle Placement

• Place internal defibrillation paddles directly on the myocardium
• Position one paddle on the right atrium or right ventricular surface
• Position the other paddle on the left ventricular apex or posterior left ventricular wall
• Ensure good contact with the myocardium but avoid excessive pressure that could cause injury
• Use saline-moistened gauze between paddles and myocardium if available to improve contact

Defibrillation Sequence

Following standard ACLS algorithms adapted for open-chest scenario 1:

1. Verify VF/pulseless VT on the monitor
2. Charge the defibrillator to 10-20 joules (internal paddles)
3. Ensure all personnel are clear of the patient and metal operating table
4. Deliver shock with paddles firmly applied to myocardium
5. Immediately resume direct cardiac compressions for 2 minutes
6. Check rhythm after 2 minutes
7. If VF/pVT persists, increase energy to 30-50 joules and repeat

Integration with CPR and Medications

During open-chest resuscitation:

• Continue direct cardiac massage (manual compression of the ventricles) between rhythm checks
• Minimize interruptions in compressions to <10 seconds 1
• Administer epinephrine intramyocardially during compressions, not during rhythm checks
• Consider amiodarone 300 mg or lidocaine 1-1.5 mg/kg IV/IO for refractory VF/pVT after the third shock 1

Key Differences from Closed-Chest Resuscitation

Energy requirements: Internal defibrillation requires dramatically lower energy (10-50 joules) compared to transthoracic defibrillation (120-200 joules biphasic or 360 joules monophasic) 1 because the paddles are in direct contact with the myocardium without chest wall impedance.

Drug delivery: Intramyocardial injection provides more direct delivery than IV/IO routes, though the same 1 mg dose is used 1, 2. Research indicates that epinephrine's hemodynamic effects may diminish with repeated doses during prolonged CPR 5, 6, so prioritize high-quality direct cardiac compressions.

Compression technique: With the chest open, perform direct cardiac massage by compressing the ventricles between your hands rather than external chest compressions.

Common Pitfalls to Avoid

• Do not use transthoracic energy levels for internal defibrillation—this will cause severe myocardial injury
• Do not inject epinephrine into the same myocardial site repeatedly—rotate injection locations to prevent tissue necrosis 4
• Do not delay defibrillation to administer epinephrine in shockable rhythms—prioritize shock delivery first 2, 7
• Do not forget to continue CPR immediately after each defibrillation attempt—resume direct cardiac massage within seconds 1