Regarding Overdose With Antidepressants....

1. A 20-year-old female presents to the ED with an overdose. She has a history of depression, and there were empty bottles found at her bedside. The bottles had contained clonazepam and nortriptyline. The patient is unconscious with diminished breathing and is unable to protect her own airway.
The BEST next step is to:
A) Intubate the patient.
B) Begin gastric lavage and administer charcoal.
C) Administer flumazenil, a benzodiazepine antagonist,
to awaken her and improve her respirations.
D) Administer bicarbonate.
E) Any of the above.

Answer and Discussion

The correct answer is “A.” This patient should be intubated.

Remember in any emergency situation that the ABCs (airway, breathing, and circulation) are the priority.

“B” is incorrect because, patients who are lavaged have a higher incidence of pulmonary aspiration—an even greater concern in the obtunded patient. In fact, airway protection is MANDATORY before undertaking lavage.

“C” is incorrect. Flumazenil will reverse the benzodiazepine. However, we know from experience that seizures in patients who have had flumazenil are particularly difficult to control. This would be particularly problematic in a patient with a mixed overdose, such as with a tricyclic, where seizures are common. Thus, it is recommended that flumazenil be used only as a reversal agent after procedural sedation in patients who are not on chronic benzodiazepines.

2. You notice that the patient begins to have an abnormal ECG tracing.
Which of the following findings would you expect to find in a tricyclic overdose?
A) Normal QRS complex.
B) Second- and third-degree heart block.
C) Widened QRS complex.
D) Sinus tachycardia.
E) Any of the above.

Answer And Discussion
The correct answer is “E.”

All of the above findings can be seen with a tricyclic overdose. In fact, the most common presenting rhythm is a narrow-complex sinus tachycardia. As toxicity progresses, you can get a prolonged PR interval, a widened QRS complex, and a prolonged QT interval. Heart blocks (second and third degree) herald a poor outcome and may be seen late in the course. Asystole is not a primary rhythm in tricyclic overdose and tends to reflect the end stage of another arrhythmia.

3. The patient becomes unresponsive and you look at the monitor. You obtain an ECG shown below:

What is the patient’s rhythm?

A) Monomorphic ventricular tachycardia.

B) Sinus tachycardia with a bundle branch block.

C) Paroxysmal supraventricular tachycardia.

D) Torsade de pointes.

E) None of the above.

Answer And Discussion

The correct answer is “D.” Torsade de pointes.

This is torsades de pointes (literally “twisting of the points”), which is a subtype of polymorphic ventricular tachycardia. It can be recognized by the varying amplitude of the complex in

a somewhat regular pattern. “A” is incorrect because the complexes are not monomorphic. “B” is incorrect for two reasons. First, there are no P waves visible. Second, sinus tachycardia should not have varied amplitude. “C” is incorrect because, again, there are no P waves and the complexes are polymorphic.

4. After taking care of the ABCs, what is the ONE BEST drug for the treatment of this arrhythmia in a patient with a tricyclic overdose?

A) Beta-blockers.

B) Lidocaine.

C) Sodium bicarbonate.

D) Procainamide.

E) Amiodarone.

Answer And Discussion

The correct answer is “C.”  Sodium bicarbonate.

The treatment of choice for arrhythmias in patients with a tricyclic overdose is sodium bicarbonate. Raising the pH and administering sodium seem to “prime” the sodium channels in the heart reversing the toxicity of the tricyclic.

Procainamide and quinidine should not be used because they act in similar fashion to tricyclics and

may worsen the problem. Lidocaine can be used as can amiodarone, but they are not the best choices.

Beta-blockers can worsen hypotension and should be avoided.

5. This is not your patient’s lucky day. She begins to seize after the administration of the bicarbonate.
The treatment of choice for this seizing patient is:
A) Lorazepam.
B) Repeat the bolus of sodium bicarbonate and start a bicarbonate drip.
C) Phenytoin (Dilantin).
D) Fosphenytoin (Cerebryx).
E) None of the above.

Answer And Discussion
The correct answer is “A.”  Lorazepam

Benzodiazepines are the treatments of choice in tricyclic-induced seizures.
While most seizures are self-limited, it is important to control seizures because the resultant acidosis can worsen tricyclic toxicity.
“B” is incorrect. This patient is already alkalinized, and sodium bicarbonate is not particularly effective in tricyclic-induced seizures. Choice “C,” phenytoin, can be used, but benzodiazepines and phenobarbital should be administered first if possible. Phenytoin is not a particularly good antiepileptic drug in tricyclic overdose. “D” is incorrect for two reasons. First, since fosphenytoin is metabolized to phenytoin, the concern about efficacy applies. Second, fosphenytoin is a prodrug and requires adequate circulation and renal and hepatic function to be converted into active drug. If our patient becomes hypotensive with poor liver and renal perfusion, adequate drug levels might not be achieved. Finally, both phenytoin and fosphenytoin can cause hypotension— not what you need in this unstable patient.

Conclusion: The patient’s seizures stop and she is admitted to the intensive care unit.