A Patient Is In Pulseless Ventricular Tachycardia. Two Shocks

Ventricular tachycardia (VT) is a rapid, life-threatening heart rhythm originating in the ventricles. When VT leads to pulselessness, it becomes a critical emergency requiring immediate intervention. Two shocks are a crucial part of the treatment algorithm in such cases. This article explores the steps, rationale, and considerations involved in managing a patient experiencing pulseless ventricular tachycardia with two shocks.

Understanding Pulseless Ventricular Tachycardia

Ventricular tachycardia is characterized by a heart rate exceeding 100 beats per minute, with the electrical activity originating from the ventricles instead of the sinoatrial (SA) node, the heart's natural pacemaker. This rapid and abnormal electrical activity impairs the heart's ability to pump blood effectively. When VT results in the absence of a palpable pulse, it signifies that the heart is not generating sufficient cardiac output to perfuse the body. This condition is termed pulseless VT and is a form of cardiac arrest.

Recognizing Pulseless VT

The recognition of pulseless VT relies on a combination of clinical signs and electrocardiographic (ECG) findings:

• Absence of Pulse: The most critical indicator is the absence of a palpable pulse in major arteries like the carotid or femoral arteries.
• Unresponsiveness: The patient will be unresponsive, as the brain is not receiving adequate blood flow.
• Apnea or Agonal Breathing: Breathing may be absent or reduced to infrequent, gasping breaths.
• ECG Findings: The ECG will show a wide QRS complex tachycardia, indicating ventricular origin. The QRS complexes are typically bizarre and irregular.

Causes of Ventricular Tachycardia

Several factors can trigger VT, including:

• Ischemic Heart Disease: Coronary artery disease, leading to myocardial infarction (heart attack), is a common cause.
• Cardiomyopathy: Diseases affecting the heart muscle, such as hypertrophic or dilated cardiomyopathy, can predispose to VT.
• Electrolyte Imbalances: Abnormal levels of potassium, magnesium, or calcium can disrupt the heart's electrical activity.
• Drug Toxicity: Certain medications, such as antiarrhythmics or tricyclic antidepressants, can induce VT.
• Long QT Syndrome: A genetic condition characterized by prolonged QT interval on the ECG, increasing the risk of ventricular arrhythmias.

Initial Management: The ACLS Algorithm

The management of pulseless VT follows the guidelines established by the American Heart Association (AHA) and other international resuscitation councils. The cornerstone of treatment is the Advanced Cardiovascular Life Support (ACLS) algorithm, which emphasizes a systematic approach to resuscitation.

1. Activate Emergency Response System

The first step is to immediately activate the emergency response system. This ensures that additional resources, including advanced medical personnel and equipment, are en route.

2. Initiate Cardiopulmonary Resuscitation (CPR)

CPR is the foundation of resuscitation efforts. High-quality CPR involves:

• Chest Compressions: Compressing the chest at a rate of 100-120 compressions per minute, with a depth of at least 2 inches (5 cm) but no more than 2.4 inches (6 cm).
• Ventilation: Providing rescue breaths at a rate of 10-12 breaths per minute, ensuring adequate chest rise.
• Minimize Interruptions: Limiting interruptions to chest compressions to less than 10 seconds.

3. Rhythm Analysis

Simultaneously with CPR, the patient's cardiac rhythm should be assessed using a defibrillator. The defibrillator analyzes the rhythm and determines if it is shockable (ventricular fibrillation or pulseless VT) or non-shockable (asystole or pulseless electrical activity).

Delivering the First Shock

If the rhythm is identified as pulseless VT, the immediate next step is to deliver a shock.

1. Preparation

• Confirm Pulselessness: Before delivering a shock, ensure that the patient is indeed pulseless.
• Ensure Safety: Verify that no one is touching the patient or the equipment. Call out "Clear!" loudly before delivering the shock to ensure everyone's safety.
• Select Energy Level: Follow the manufacturer's recommendations for the appropriate energy level. For biphasic defibrillators, the initial recommended dose is typically 120-200 joules. For monophasic defibrillators, the recommended dose is 360 joules.

2. Shock Delivery

• Apply Pads: Apply the defibrillator pads to the patient's chest in one of two positions:
  • Anterolateral: One pad is placed below the right clavicle, and the other pad is placed at the left mid-axillary line, below the armpit.
  • Anteroposterior: One pad is placed on the anterior chest, and the other pad is placed on the posterior chest between the scapulae.
• Deliver Shock: Press the "discharge" button to deliver the electrical shock.
• Resume CPR Immediately: Do not delay CPR to reassess the rhythm. Immediately resume chest compressions, starting with the first compression.

Post-Shock Management and Rhythm Reassessment

Following the first shock, it is crucial to continue CPR without interruption for two minutes before reassessing the rhythm.

1. Continue CPR

Continue high-quality CPR for two minutes. This allows for myocardial perfusion and increases the chances of successful defibrillation.

2. Rhythm Analysis After Two Minutes

After two minutes of CPR, pause briefly to reassess the patient's rhythm. If the rhythm remains pulseless VT, proceed to the second shock.

Delivering the Second Shock

If the rhythm persists as pulseless VT after the first shock, a second shock is indicated.

1. Preparation

• Ensure Safety: As before, ensure that no one is touching the patient or the equipment. Call out "Clear!" before delivering the shock.
• Select Energy Level: Use the same energy level as the first shock. If the first shock was effective in converting the rhythm but the patient reverted back to VT, consider increasing the energy level for the second shock.

2. Shock Delivery

• Deliver Shock: Press the "discharge" button to deliver the second electrical shock.
• Resume CPR Immediately: Do not delay CPR to reassess the rhythm. Immediately resume chest compressions, starting with the first compression.

Post-Second Shock Management

Following the second shock, continue CPR for another two minutes before reassessing the rhythm. During this period, additional interventions should be initiated.

1. Continue CPR

Continue high-quality CPR for two minutes.

2. Establish Intravenous (IV) Access

Establish IV access to administer medications.

3. Administer Medications

The ACLS algorithm recommends administering medications during CPR.

• Epinephrine: Administer epinephrine 1 mg intravenously every 3-5 minutes. Epinephrine is a vasopressor that increases coronary and cerebral blood flow.
• Antiarrhythmics: Consider administering an antiarrhythmic medication such as amiodarone or lidocaine.
  • Amiodarone: The recommended dose is 300 mg IV bolus, followed by a second dose of 150 mg IV if needed.
  • Lidocaine: The recommended dose is 1-1.5 mg/kg IV bolus.

4. Address Reversible Causes

Identify and treat any reversible causes of cardiac arrest, often referred to as the "Hs and Ts":

• Hypovolemia: Low blood volume
• Hypoxia: Low oxygen levels
• Hydrogen ion (acidosis): Acid-base imbalance
• Hypokalemia or Hyperkalemia: Potassium imbalance
• Hypothermia: Low body temperature
• Tension pneumothorax: Air accumulation in the chest cavity
• Tamponade (cardiac): Fluid accumulation around the heart
• Toxins: Drug overdose or poisoning
• Thrombosis (coronary or pulmonary): Blood clot in the heart or lungs

5. Rhythm Analysis After Two Minutes

After two minutes of CPR, pause briefly to reassess the patient's rhythm. If the rhythm remains pulseless VT, continue alternating between CPR, defibrillation, and medication administration.

Subsequent Shocks and Advanced Interventions

If the patient remains in pulseless VT after the second shock, continue the ACLS algorithm. Subsequent shocks should be delivered with the same energy level as the first two shocks. Consider increasing the energy level if the rhythm is refractory to initial shocks.

Advanced Airway Management

Consider advanced airway management techniques, such as endotracheal intubation or the use of a supraglottic airway device, to optimize ventilation.

Transcutaneous Pacing

If the patient converts to a perfusing rhythm but is bradycardic (slow heart rate), transcutaneous pacing may be necessary to maintain adequate cardiac output.

Consultation with Specialists

Consultation with cardiology or critical care specialists may be beneficial in managing complex cases of pulseless VT.

Factors Affecting Defibrillation Success

Several factors can influence the success of defibrillation:

• Time to Defibrillation: The sooner defibrillation is performed, the higher the chances of successful conversion to a perfusing rhythm.
• CPR Quality: High-quality CPR improves myocardial perfusion and increases the likelihood of successful defibrillation.
• Electrode Placement: Proper placement of defibrillation pads is essential to ensure adequate current flow through the heart.
• Energy Level: Using the appropriate energy level is crucial for successful defibrillation.
• Patient Factors: Factors such as body weight, chest size, and underlying cardiac conditions can affect defibrillation success.

Potential Complications

While defibrillation is a life-saving intervention, it is not without potential complications:

• Skin Burns: Defibrillation can cause skin burns at the site of electrode placement.
• Myocardial Damage: In rare cases, defibrillation can cause myocardial damage, particularly with repeated shocks.
• Arrhythmias: Defibrillation can sometimes induce other arrhythmias, such as asystole or bradycardia.
• Embolic Events: Defibrillation can dislodge blood clots, leading to embolic events such as stroke or pulmonary embolism.

Ethical Considerations

In some cases, resuscitation efforts may be futile. Ethical considerations should guide decisions regarding the continuation or termination of resuscitation. Factors to consider include:

• Patient's Wishes: If the patient has expressed wishes regarding resuscitation, these should be respected.
• Underlying Medical Conditions: The presence of severe, irreversible medical conditions may make resuscitation futile.
• Duration of Arrest: Prolonged cardiac arrest with no response to treatment may indicate a poor prognosis.

Conclusion

Pulseless ventricular tachycardia is a life-threatening emergency requiring immediate and coordinated intervention. Two shocks are a critical component of the ACLS algorithm for managing this condition. High-quality CPR, prompt defibrillation, medication administration, and identification of reversible causes are essential for improving patient outcomes. Understanding the rationale behind each step in the algorithm and the factors that influence defibrillation success is crucial for healthcare professionals involved in resuscitation efforts. Continuous training and adherence to established guidelines are necessary to optimize the management of pulseless VT and increase the chances of survival.