A 45-year-old woman is brought to the emergency department by ambulance after a neighbor found her in an obtunded state and with an empty bottle of medication next to her. The patient had a tonic-clonic seizure en route to the hospital. Medical history is significant for major depression and chronic back pain. Temperature is 38.3 C (100.9 F), blood pressure is 90/70 mm Hg, pulse is 120/min, and respirations are 16/min. The patient responds to painful stimuli. Bilateral pupils are 8 mm. The skin is warm and flushed. The lungs are clear to auscultation. The abdomen is soft and nontender. Bowel sounds are decreased. There is no neck stiffness. ECG shows QRS duration of 130 msec, increased from a month ago. Which of the following is the most appropriate next step in management of this patient?

Question

A 45-year-old woman is brought to the emergency department by ambulance after a neighbor found her in an obtunded state and with an empty bottle of medication next to her.  The patient had a tonic-clonic seizure en route to the hospital.  Medical history is significant for major depression and chronic back pain.  Temperature is 38.3 C (100.9 F), blood pressure is 90/70 mm Hg, pulse is 120/min, and respirations are 16/min.  The patient responds to painful stimuli.  Bilateral pupils are 8 mm.  The skin is warm and flushed.  The lungs are clear to auscultation.  The abdomen is soft and nontender.  Bowel sounds are decreased.  There is no neck stiffness.  ECG shows QRS duration of 130 msec, increased from a month ago.  Which of the following is the most appropriate next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d1e0_7e6e_bc81_d516436578c9_MD0003_00 This patient's history of depression, coupled with her presenting symptoms, suggests she has overdosed on tricyclic antidepressants (TCAs). TCA overdose can cause anticholinergic effects (eg, hyperthermia, flushed skin, dilated pupils, decreased bowel sounds), seizures, and cardiac toxicity (eg, prolonged QRS interval, hypotension). TCA overdose blocks the cardiac fast sodium channels and decreases myocardial conduction velocity, leading to QRS prolongation and risk of ventricular arrhythmia. Cardiac toxicity and TCA-induced hypotension, which can be refractory to management, are the major causes of mortality in TCA overdose. Management of TCA overdose begins with supportive care (eg, securing airway, breathing, circulation) and cardiac monitoring. If cardiac toxicity is present, it is managed as follows: Hypotension is treated with isotonic saline boluses; refractory hypotension may require vasopressors (eg, norepinephrine). QRS prolongation or ventricular arrhythmias are treated with intravenous sodium bicarbonate. Sodium bicarbonate (recommended with QRS >100 msec) narrows the QRS complex and decreases the incidence of ventricular arrhythmia; it has also been shown to improve hypotension. The mechanism of action of sodium bicarbonate is thought to be due to the increased sodium load overcoming TCA blockade of cardiac sodium channels, as well as to the alkalinization of the serum, which makes the TCA less pharmacologically active. (Choice A) Atropine and pralidoxime are the proper antidotes for anticholinesterase toxicity, as seen in organophosphate poisoning. In contrast to this patient, those with cholinergic toxicity typically have bradycardia, miosis, and salivation. (Choice B) Calcium gluconate is cardioprotective in cases of hyperkalemia. Hyperkalemia presents on ECG as peaked T waves, followed by lengthening of the PR and QRS intervals, and eventually resulting in a sine wave. Bradycardia and muscle weakness, not present in this case, are commonly seen in hyperkalemia. (Choice C) Magnesium sulfate is used in patients who have torsade de pointes induced by a prolonged QT interval, not a prolonged QRS interval. (Choice D) Naloxone reverses opioid intoxication, which would cause miosis (rather than mydriasis) and is less likely to cause hyperthermia, skin flushing, or QRS prolongation as compared to TCA overdose. Educational objective: Tricyclic antidepressant overdose can cause anticholinergic symptoms, central nervous system toxicity (eg, seizures), and cardiac toxicity (eg, hypotension, QRS prolongation). Patients with QRS prolongation should receive sodium bicarbonate to narrow the QRS interval, prevent ventricular arrhythmia, and improve hypotension. References: Tricyclic antidepressant overdose: a review. (http://www.ncbi.nlm.nih.gov/pubmed/11435353) A literature review of the use of sodium bicarbonate for the treatment of QRS widening. (http://www.ncbi.nlm.nih.gov/pubmed/26159649) Tricyclic antidepressant toxicity. (http://www.ncbi.nlm.nih.gov/pubmed/28613681)

A 45-Year-Old Woman Is Brought to the Emergency Department by Ambulance