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Difficulty: HardPharmacologic Interventions

Emergency medical services transport a 29-year-old female to the resuscitation bay following an intentional pharmaceutical ingestion. Empty pill bottles for amitriptyline and sustained-release diltiazem were found beside her. On arrival, she is lethargic and responds only to painful stimuli. Vital signs include a temperature of 36.8°C (98.2°F), blood pressure of 78/40 mm Hg, heart rate of 52/min, and respiratory rate of 14/min. Physical examination is notable for dry mucous membranes, mydriasis, and delayed capillary refill. An electrocardiogram reveals sinus bradycardia with a PR interval of 240 ms, a QRS duration of 145 ms, and a QTc interval of 510 ms. Bedside capillary blood glucose is 142 mg/dL. Intravenous fluid resuscitation is commenced. Which of the following pharmacologic interventions are most appropriate to initiate next? (Select all that apply)

  1. Intravenous sodium bicarbonateAnswer
  2. Intravenous high-dose insulin and glucoseAnswer
  3. C
    Intravenous physostigmine
  4. D
    Intravenous flumazenil
  5. E
    Intravenous amiodarone

Answer

The most appropriate interventions are intravenous sodium bicarbonate and intravenous high-dose insulin and glucose.
This patient presents with a life-threatening mixed overdose of a tricyclic antidepressant (amitriptyline) and a non-dihydropyridine calcium channel blocker (diltiazem). The electrocardiogram shows a QRS of 145 ms, which is highly predictive of imminent ventricular dysrhythmias in TCA toxicity. Intravenous sodium bicarbonate is the standard of care to overcome the sodium channel blockade and narrow the QRS. Concurrently, the profound hypotension and bradycardia indicate severe calcium channel blocker toxicity. Intravenous high-dose insulin (with glucose to prevent hypoglycemia) acts as a robust positive inotrope, bypassing the blocked calcium channels by improving myocardial carbohydrate utilization and restoring cardiac output.

Step-by-Step Solution

1
Identify the primary pathophysiologic derangements based on the ingested agents.
The patient exhibits anticholinergic toxicity and sodium channel blockade (wide QRS) from amitriptyline, alongside cardiogenic shock and conduction delay (bradycardia, prolonged PR) from diltiazem.
Recognizing the dual toxidrome dictates the need for simultaneous, targeted antidotal therapies.
2
Determine the appropriate intervention for the tricyclic antidepressant (TCA) toxicity.
Intravenous sodium bicarbonate is indicated.
A QRS duration >100 ms in the setting of TCA overdose is a strong predictor of ventricular dysrhythmias; sodium bicarbonate provides a sodium load and alkalization to overcome the channel blockade.
3
Determine the appropriate intervention for the calcium channel blocker (CCB) toxicity.
Intravenous high-dose insulin and glucose is indicated.
The patient is in distributive and cardiogenic shock refractory to initial fluids. High-dose insulin serves as a powerful inotrope by facilitating myocardial glucose uptake, which is impaired during CCB toxicity.

Key Concept

Management of mixed pharmaceutical overdoses requires identifying specific life-threatening electrocardiographic and hemodynamic derangements (e.g., wide QRS, cardiogenic shock) and utilizing targeted antidotes while strictly avoiding agents that exacerbate the underlying toxicities.
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Topics

Pharmacologic Interventions

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