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Difficulty: MediumPharmacologic Interventions

Emergency medical services arrive at the resuscitation bay with an unresponsive adult found unconscious in an apartment. The roommate reports that multiple empty, unlabeled medication bottles were scattered on the bedside table. Initial vital signs show a blood pressure of 90/50 mmHg, a pulse of 112/min, and a respiratory rate of 6/min. Physical examination reveals miotic pupils, decreased bowel sounds, and generalized hyperreflexia. A 12-lead electrocardiogram is rapidly obtained, demonstrating sinus tachycardia with a QRS complex duration of 145 msec and a prominent terminal R wave in lead aVR. Based on the patient's presentation and diagnostic findings, which of the following pharmacologic interventions are indicated for immediate management? (Select all that apply)

  1. Intravenous naloxoneAnswer
  2. Intravenous sodium bicarbonateAnswer
  3. C
    Intravenous physostigmine
  4. D
    Intravenous flumazenil
  5. E
    Intravenous amiodarone

Answer

Intravenous naloxone and Intravenous sodium bicarbonate
The patient exhibits a mixed toxidrome characteristic of simultaneous opioid and tricyclic antidepressant (TCA) toxicity. The markedly depressed respiratory rate and miotic pupils strongly suggest opioid intoxication, warranting the administration of intravenous naloxone to reverse central respiratory depression. Simultaneously, the presence of tachycardia, generalized hyperreflexia, and a widened QRS complex (>100 msec) with a terminal R wave in lead aVR indicates TCA toxicity. TCAs cause competitive sodium channel blockade, which prolongs phase 0 of the myocardial action potential and widens the QRS complex, predisposing the patient to lethal ventricular arrhythmias. Intravenous sodium bicarbonate is indicated to overcome this blockade by providing a large sodium load and increasing the serum pH, thereby preventing or treating TCA-induced arrhythmias.

Step-by-Step Solution

1
Analyze the vital signs and physical examination findings to identify the toxidrome.
The respiratory rate of 6/min and miotic pupils are hallmark signs of opioid intoxication.
Recognizing severe respiratory depression prioritizes the immediate need for airway protection or reversal agents.
2
Interpret the electrocardiogram and remaining physical exam findings in the context of an unknown overdose.
Tachycardia, generalized hyperreflexia, and a QRS duration of 145 msec with a terminal R wave in aVR indicate concurrent tricyclic antidepressant (TCA) toxicity.
A widened QRS (>100 msec) in an overdose setting is a strong predictor of TCA-induced arrhythmias and seizures.
3
Select the appropriate targeted pharmacologic antidotes while avoiding contraindicated agents.
Naloxone is selected for the opioid-induced respiratory depression, and sodium bicarbonate is selected to treat the TCA-induced sodium channel blockade.
Simultaneous management of mixed life-threatening toxidromes requires specific antidotal therapy while avoiding medications that exacerbate the underlying poisonings.

Key Concept

Management of mixed opioid and tricyclic antidepressant overdose
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Topics

Pharmacologic Interventions

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