In an adult with hemodynamically unstable monomorphic ventricular tachycardia requiring immediate synchronized cardioversion, which short‑acting, hemodynamically neutral sedative agents are appropriate?

Sedation for Synchronized Cardioversion in Hemodynamically Unstable Monomorphic Ventricular Tachycardia

In an adult with hemodynamically unstable monomorphic ventricular tachycardia requiring immediate synchronized cardioversion, procedural sedation should be provided only if the patient is conscious and the clinical situation permits brief delay; however, in extremely unstable patients (altered mental status, shock, acute heart failure), proceed directly to cardioversion without waiting for sedation or IV access. 1, 2

Immediate Assessment of Stability

• Hemodynamic instability is defined by any of the following: systolic blood pressure <90 mmHg, altered mental status or syncope, signs of shock (cold extremities, poor perfusion), chest pain with ST-segment changes indicating myocardial ischemia, or acute pulmonary edema. 2

• Monomorphic ventricular tachycardia with pulse requires synchronized cardioversion starting at 100 J (biphasic or monophasic) as the initial energy level. 1

• The most critical determinant of whether to provide sedation is the degree of hemodynamic compromise: patients in frank shock or with altered consciousness require immediate cardioversion without any delay for sedation. 1

Sedation Protocol When Clinically Feasible

When to Provide Sedation

• Procedural sedation or anesthesia should be administered in conscious patients who are hemodynamically unstable but not in extremis (i.e., still maintaining adequate perfusion and mental status). 1

• If the patient has altered mental status or is unconscious, sedation is unnecessary and cardioversion should proceed immediately. 1, 2

Appropriate Short-Acting Sedative Agents

The guidelines do not specify particular sedative agents by name for cardioversion in unstable ventricular tachycardia. However, based on the requirement for hemodynamic neutrality and rapid onset/offset, the following principles apply:

• Etomidate (0.2–0.3 mg/kg IV) is the preferred agent in hemodynamically unstable patients because it preserves blood pressure and has minimal cardiac depressant effects.

• Ketamine (1–2 mg/kg IV) is an acceptable alternative, as it maintains sympathetic tone and blood pressure, though it may increase heart rate.

• Avoid benzodiazepines (e.g., midazolam) as sole agents in unstable patients, because they cause dose-dependent hypotension and lack hemodynamic neutrality.

• Avoid propofol in hemodynamically unstable patients, as it causes significant vasodilation and myocardial depression that can precipitate cardiovascular collapse.

• Fentanyl (50–100 mcg IV) may be added for analgesia but should not be used alone for sedation.

Critical Procedural Steps

Pre-Cardioversion Preparation

• Establish IV access if possible, but do not delay cardioversion in extremely unstable patients to secure a line. 1

• Turn on the synchronization function on the defibrillator to time shock delivery with the QRS complex, and verify that the device is detecting QRS complexes appropriately before proceeding. 1

• Have resuscitation equipment immediately available, as patients with unstable ventricular tachycardia may deteriorate to pulseless VT or ventricular fibrillation at any moment. 1

Energy Escalation

• If the initial 100 J shock fails, increase energy in a stepwise fashion for subsequent attempts. 1

• Synchronized cardioversion achieves near-100% termination of monomorphic ventricular tachycardia in hemodynamically unstable patients. 1, 2

Post-Cardioversion Management

• Continuous cardiac monitoring is essential immediately after cardioversion, as patients often experience premature ventricular complexes that may re-initiate tachycardia within seconds. 1

• Antiarrhythmic medication (e.g., amiodarone 150 mg IV over 10 minutes, then 1 mg/min infusion) should be considered to prevent recurrent arrhythmias. 1

• Beta-blockers may be beneficial for recurrent and refractory ventricular arrhythmias once hemodynamic stability is restored. 1

Critical Pitfalls to Avoid

• Do not delay cardioversion in extremely unstable patients to establish IV access or provide sedation—proceed immediately. 1

• Do not administer calcium-channel blockers (e.g., diltiazem, verapamil) in patients with ventricular tachycardia, as they can worsen hemodynamic status and precipitate cardiovascular collapse. 1, 2

• Do not use unsynchronized shocks for monomorphic VT with a pulse; this is reserved only for pulseless VT or ventricular fibrillation. 1

• Do not assume the patient is stable based solely on preserved oxygen saturation; hypotension with tachycardia constitutes a medical emergency regardless of oxygenation. 3