A 34-year-old man is brought to the emergency department by police due to severe agitation… — USMLE Step 3

A 34-year-old man is brought to the emergency department by police due to severe agitation and aggressive behavior. He was found wandering in traffic, yelling at passing vehicles. In the emergency department, he is pacing rapidly, responding to internal stimuli, and attempting to strike staff members. He completely refuses to take any oral medications. His medical history is significant for schizophrenia, alcohol use disorder, and a recent hospital admission for an episode of syncope. Discharge records from that admission reveal a normal echocardiogram but a 12-lead ECG demonstrating sinus bradycardia with a corrected QT (QTc) interval of $540 \text{ ms}$ . Vital signs are temperature $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure $142/88 \text{ mmHg}$ , heart rate $94\text{/min}$ , and respiratory rate $18\text{/min}$ . Which of the following is the most appropriate initial pharmacologic intervention to manage this patient's acute agitation?

Intramuscular lorazepamAnswer
B
Intramuscular haloperidol
C
Intramuscular ziprasidone
D
Intramuscular chlorpromazine
E
Oral risperidone

Answer

Intramuscular lorazepam

This patient requires immediate chemical restraint due to severe agitation, aggressive behavior, and risk of harm to staff. However, his baseline QTc interval is

540 \text{ ms}

(normal is typically

< 440 \text{ ms}

in men), placing him at extreme risk for Torsades de pointes and sudden cardiac death if QTc-prolonging medications are administered. Benzodiazepines, such as intramuscular lorazepam, provide effective rapid sedation and have no effect on the QT interval. Therefore, lorazepam is the safest and most appropriate pharmacologic choice in this specific clinical scenario.

Step-by-Step Solution

Assess the clinical urgency and patient cooperation.

The patient requires immediate chemical restraint due to violence, and the intramuscular route is required because he refuses oral medications.

Ensures physical safety of the patient and staff while avoiding unfeasible delivery methods.

Review the patient's medical history for contraindications to standard therapies.

The patient has a documented baseline QTc interval of 540 ms.

Standard chemical restraints (antipsychotics) carry a risk of QTc prolongation and fatal arrhythmias.

Select an appropriate sedative agent that does not exacerbate the underlying cardiac risk.

Intramuscular lorazepam is chosen.

Benzodiazepines provide effective sedation for acute agitation without affecting ventricular repolarization (QT interval).

Key Concept

Management of acute agitation in patients with baseline prolonged QTc utilizing benzodiazepines to avoid fatal arrhythmias.

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