Examkin

Question

Difficulty: HardInitial Stabilization and Triage

A 24-year-old female is rushed to the resuscitation bay by her college roommate, who discovered her in a highly lethargic state in their dormitory. An empty bottle of amitriptyline was found on her bedside table. Upon evaluation, the patient is somnolent and disoriented but spontaneously maintains a patent airway and localizes to painful stimuli. Her past medical history is notable for recurrent major depressive disorder and generalized anxiety. Current vital signs show a temperature of 38.2°C (100.8°F), heart rate of 138/min, blood pressure of 78/48 mm Hg, respirations of 14/min, and pulse oximetry of 96% on ambient air. Physical examination reveals mydriasis, dry oral mucosa, and a complete absence of bowel sounds. A stat electrocardiogram displays a wide-complex sinus tachycardia with a QRS duration of 145 ms and a prominent terminal R wave in lead aVR. Which of the following represents the most urgent initial step in the stabilization of this patient?

  1. Intravenous administration of sodium bicarbonateAnswer
  2. B
    Intravenous administration of physostigmine
  3. C
    Intravenous administration of amiodarone
  4. D
    Noncontrast computed tomography of the head
  5. E
    Urgent cardiology consultation

Answer

Intravenous administration of sodium bicarbonate
The correct answer is the administration of intravenous sodium bicarbonate. This patient presents with a severe tricyclic antidepressant (TCA) overdose, evidenced by the ingestion history and classic anticholinergic signs (altered mental status, tachycardia, mydriasis, absent bowel sounds). TCAs are highly toxic to the cardiovascular system because they competitively block fast sodium channels in the His-Purkinje system and the myocardium. This blockade leads to delayed depolarization, which manifests on an electrocardiogram as a widened QRS complex and a prominent terminal R wave in lead aVR. Clinical guidelines mandate the immediate administration of intravenous sodium bicarbonate for TCA toxicity when a patient experiences hypotension or has a QRS duration greater than 100 ms. Sodium bicarbonate provides a massive sodium gradient that overcomes the competitive receptor blockade, while concurrently alkalinizing the serum (target pH 7.45-7.55), which increases the non-ionized fraction of the TCA drug, further reducing its binding affinity to cardiac sodium channels. This critical step must be performed before any imaging studies or specialty consultations are requested.

Step-by-Step Solution

1
Identify the underlying toxidrome causing the patient's instability.
The patient presents with severe anticholinergic toxicity (mydriasis, dry mucosa, ileus, tachycardia) resulting from an overdose of amitriptyline, a tricyclic antidepressant (TCA).
Accurate identification of the specific ingestion directs the critical pathways for antidote administration and stabilization.
2
Analyze the electrocardiogram and vital signs for life-threatening complications.
The patient is in profound shock (blood pressure 78/48 mm Hg) and the ECG reveals a QRS duration of 145 ms with a terminal R wave in aVR.
TCAs block fast cardiac sodium channels, causing QRS widening and myocardial depression. A QRS duration greater than 100 ms or the presence of hypotension predicts a high risk for fatal ventricular arrhythmias.
3
Determine the most appropriate immediate stabilization step.
Administer intravenous sodium bicarbonate.
Sodium bicarbonate directly counters the sodium channel blockade and alkalinizes the serum to reduce TCA receptor binding, stabilizing the myocardium before any diagnostic imaging or specialist consultations occur.

Key Concept

Patients presenting with tricyclic antidepressant cardiotoxicity—indicated by hypotension or a QRS duration greater than 100 ms—require immediate stabilization with intravenous sodium bicarbonate to prevent fatal arrhythmias.
Rate this question

Topics

Initial Stabilization and Triage

More questions from this topic