Tricyclic Antidepressant Overdose

: Audience: Emergency medicine residents and medical students on emergency medicine rotations.


Linked objectives and methods:
TCA overdose is a rare occurrence but an essential diagnosis which can be effectively taught through the oral board or simulation format. The oral board format allows faculty to observe the learner in real time to ensure that critical information is gained in order to ensure the learner can differentiate between causes of altered mental status and use critical information in the case to arrive at a toxidrome as the cause of altered mental status.
In the initial evaluation, the learner should initiate a detailed workup of the broad differentials of a patient with altered mental status (objective 1). Early in the case, the learner should order and review the ECG, recognizing the classic ECG findings of TCA overdose (objective 2 and 3). The learner should identify the TCA overdose toxidrome and discuss the appropriate urgent management and treatment (objective 4). Lastly, the learner should provide appropriate disposition of the patient to an intensive care unit (objective 5). Debriefing will ensure that the learner can assimilate all of the sources data in a coherent picture to deduce the correct diagnosis and will review any missed points or concepts.
Recommended pre-reading for instructor: •

Results and tips for successful implementation:
This case is best used for oral board testing and assessment. It can be part of a single-case or implemented into a triple-case setting. It is challenging for interns and junior residents due to the rarity of the pathophysiology. It is appropriate for the testing of higher-level differential diagnoses in an altered patient, and for rapid-decision-making in an ongoing resuscitation. The case has been trialed on 20 learners as a single-case. Junior and senior learners alike had difficulty with the appropriate diagnosis based on lack of familiarity with the diagnosis. Senior learners tended to understand the pathophysiology and were able to successfully progress to case resolution. Medical students and interns did not have complete understanding, and often the progression led to an assessment of their advanced cardiac life support (ACLS) knowledge. This was also useful, and the examiners were able to redirect most of the cases to a TCA diagnosis. All learners appreciated seeing this case in a simulation-type setting, and the feedback was positive. We recommend using this case in conjunction with a toxicology module to reinforce the broad differential diagnoses associated with altered mental status and potential overdose.

Objectives:
By the end of this oral boards session, learners will be able to: 1. Discuss the appropriate laboratory testing and workup for a patient with undifferentiated altered mental status 2. Discuss the importance of obtaining an ECG in a timely manner in order to investigate the broad differential of altered mental status 3. Identify the classic ECG findings of a patient with TCA overdose 4. Review the treatment of TCA overdose 5. Discuss the appropriate disposition of a patient with TCA overdose Case Summary: This is a 31-year-old male patient who was found to be altered and incoherent in his parked car. He had been found by coworkers, babbling to himself. He had recently been complaining of "not feeling well" and "not enjoying his job." He had been married and divorced, all within the last year. His coworkers told emergency medical services (EMS) that he was withdrawn at work, and they knew very little about him. He needs early and aggressive care, which includes an emergent ECG, which clinches the diagnosis of TCA overdose. He requires sodium bicarbonate boluses and drip, and will need toxicology consultation and ICU admission.

Order of Case:
This is a case of intentional tricyclic antidepressant overdose. The patient is initially altered and the only history can be obtained from EMS. The patient has undifferentiated altered mental status, and the key is obtaining a challenging history and using the early ECG interpretation to elicit the diagnosis.
If the ECG pattern of TCA overdose is not recognized early, the patient will decompensate, have worsening ECG changes, and require aggressive hemodynamic resuscitation that can only be recovered with sodium bicarbonate therapy. The examiner should provide worsening vital signs, including profound hypotension and tachycardia, and the patient will become unresponsive. Stimulus #9 should be offered to the examinee, spontaneously obtained by the nurse. If TCA-overdose is still unrecognized, the patient should deteriorate into cardiac arrest (the nurse can announce that the patient no longer has a pulse or a blood pressure). The examinee should be required to perform ACLS; however, the patient will not have return of spontaneous circulation until at least two ampules of sodium bicarbonate are given.
If recognized early, the overdose can be treated appropriately; the patient will improve, and can be safely admitted to the hospital. Toxicology should be consulted but will not be able to provide the precise diagnosis or assistance in treatment because this is a bedside diagnosis that should be made by the emergency physician.
Disposition: Admit to medical intensive care unit (MICU).

Historical Information Chief Complaint: Confusion
History of present illness: This is a previously healthy 31-year-old male patient who presents with chief complaint of confusion. The patient was found by his coworkers in the parking lot at work and EMS was called. Learner should request that EMS remain to provide further history. If EMS remains, they may relate that per coworkers the patient has been married and divorced, all within the last year. He has been withdrawn and kept to himself at work. He previously attended social events, but lately has not been interested in any social activities. He is otherwise unable to provide any information and babbles incoherently while in the examination room.