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Zorluk: Çok zorInitial Stabilization and Triage

A university student is rushed to the resuscitation bay after being discovered seizing in a dormitory. Scattered empty bottles of amitriptyline and diphenhydramine were located nearby. The patient is currently exhibiting continuous generalized tonic-clonic movements. Physical examination reveals flushed, dry skin and symmetrically dilated pupils. Continuous monitoring displays a pulse of 142/min, blood pressure of 76/40 mm Hg, and oxygen saturation of 92% on room air. An electrocardiogram rhythm strip shows a wide-complex sinus tachycardia with a QRS duration of 165165 msec and a prominent terminal R wave in lead aVR.

Which of the following are the MOST appropriate simultaneous initial stabilization steps? (Select 2)

  1. Administration of intravenous sodium bicarbonateCevap
  2. Administration of intravenous lorazepamCevap
  3. C
    Administration of intravenous physostigmine
  4. D
    Administration of intravenous amiodarone
  5. E
    Acquisition of a stat non-contrast cranial computed tomography

Cevap

The most appropriate simultaneous initial stabilization steps are the administration of intravenous sodium bicarbonate and intravenous lorazepam.
The patient presents with severe tricyclic antidepressant (TCA) toxicity, characterized by anticholinergic symptoms, seizures, profound hypotension, and cardiac sodium channel blockade (indicated by the QRS duration >100>100 msec and the prominent terminal R wave in lead aVR). Initial stabilization must simultaneously address the seizures and the impending cardiac arrest. Seizures produce lactic acid, which lowers serum pH; acidemia significantly worsens the binding of the TCA to cardiac sodium channels, creating a lethal feedback loop. Therefore, rapid termination of the seizure with a benzodiazepine (e.g., lorazepam) is a critical stabilization step. Concurrently, intravenous sodium bicarbonate must be administered to overcome the sodium channel blockade. Bicarbonate achieves this via two mechanisms: providing a massive sodium concentration gradient to outcompete the drug at the receptor, and alkalinizing the serum to decrease the drug's binding affinity. Both of these pharmacological interventions are life-saving and represent the cornerstone of initial triage and stabilization for this presentation.

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1
Identify the life-threatening toxidrome and pathophysiology.
The clinical picture indicates a mixed anticholinergic and tricyclic antidepressant (TCA) overdose, complicated by active seizures and severe cardiotoxicity (hypotension, widened QRS, terminal R wave in aVR).
Recognizing the specific toxicological mechanism (fast sodium channel blockade) dictates the immediate choice of antidotes.
2
Address the active seizures immediately.
Intravenous lorazepam is indicated to terminate the generalized tonic-clonic activity.
Seizures generate lactic acid, lowering serum pH. Acidemia increases the fraction of ionized TCA, which binds more strongly to cardiac sodium channels, rapidly worsening cardiovascular collapse.
3
Stabilize the myocardium simultaneously.
Intravenous sodium bicarbonate is indicated to treat the wide-complex tachycardia.
Sodium bicarbonate provides a high sodium load to overcome the competitive channel blockade and alkalinizes the serum, which favors the un-ionized form of the TCA, decreasing its binding affinity to the sodium channels.

Anahtar Kavram

Initial stabilization of life-threatening tricyclic antidepressant (TCA) overdose requires simultaneous administration of sodium bicarbonate (to reverse sodium channel blockade and stabilize the myocardium) and benzodiazepines (to terminate seizures and prevent exacerbating acidemia), while strictly avoiding contraindicated agents like physostigmine and standard antiarrhythmics.
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Initial Stabilization and Triage

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