Tricyclic Antidepressant Toxicity in Emergency Medicine Workup

  • Author: Vivian Tsai, MD, MPH; Chief Editor: Asim Tarabar, MD   more...
 
Updated: Mar 26, 2010
 

Laboratory Studies

  • Studies have shown that serum cyclic antidepressant (CA) level does not correlate well with severity of CA toxicity and is a poor predictor of clinical outcome.
  • Because multisubstance ingestion is common, routine screening for other potentially treatable toxins is recommended (eg, acetaminophen). Request for the other serum toxicologic levels should be guided based on the clinical picture. For example, in patients with acidosis, assess for aspirin, ethylene glycol, and methanol.
  • Assess the following:
    • Electrolyte, BUN, and creatinine levels
    • Anion gap
    • CBC count
    • Alcohol level
    • ABGs for evaluation of acidosis or hypoxia
  • Point-of-care qualitative urine immunoassays are available. They detect the presence of CA in the body. Test results are positive for most TCAs in the subtherapeutic-to-toxic range, with the exception of clomipramine. False-positive results due to cross-reactivity occur in patients who are also taking cyclobenzaprine. These tests are helpful when patients' medication lists are unknown and CA toxicity is suspected based on history, clinical presentation, and ECG findings. However, in patients known to take TCAs, the urine immunoassays are of limited use because the result does not correlate with serum CA levels.[4]
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Imaging Studies

  • Chest radiography should be performed in cases of suspected aspiration or when respiratory symptoms are noted and may be used to rule out other causes of fever, tachycardia, and altered mental status.
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Other Tests

Sinus tachycardia is the most common ECG finding in CA toxicity.

  • Measurement of limb-leads QRS duration can be used to assess the severity of CA exposure. A QRS interval greater than 100 milliseconds is the basis for treatment with bicarbonate (alkalinization).
  • Patients with a QRS interval less than 100 milliseconds are unlikely to develop seizures and arrhythmias. Patients with a QRS interval greater than 100 milliseconds have up to a 34% chance of developing seizures and up to a 14% chance of developing a life-threatening cardiac arrhythmia. With a QRS complex greater than 160 milliseconds, the chance of ventricular arrhythmias increases to 50%.
  • The amplitude of the R wave in lead aVR and the ratio of the R/S waves in aVR are greater in patients who developed seizures or dysrhythmias.
  • According to Liebelt et al, when the R wave in aVR equals 3 mm or more, the sensitivity and specificity for subsequent development of seizures or arrhythmias are 81% and 73%, respectively.[5]
  • ECG findings that can be observed in CA toxicity include sinus tachycardia; prolongation of the PR, QRS, and QTc intervals; nonspecific ST-segment and T-wave changes; AV block; right-axis deviation of the terminal 40-millisecond vector of the QRS complex in the frontal plane; and the Brugada pattern (downsloping ST-segment elevation in leads V1-V3 in association with right bundle branch block).[6]
  • A Brugada pattern was seen using ECG in 17% of patients with TCA toxicity in a retrospective study completed by Monteban-Kooistra et al.[7] The ECG finding abnormalities resolved after administration of sodium bicarbonate.
  • A study of 98 consecutive cases of CA intoxication in France found that the mortality rate was 6.7% among patients with the Brugada electrocardiographic pattern and 2.4% among patients without it. However, the result is not statistically significant (p=0.39).[8]
  • Early recognition of conduction disturbances is important in suspected CA poisoning.
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Procedures

  • GI decontamination may be helpful within the first several hours postingestion because CAs can slow gastric emptying through the anticholinergic activity.
    • Gastric lavage may be helpful in recovering and identifying the CA ingested. However, one study that compared the use of gastric lavage and activated charcoal versus charcoal alone showed no benefit in clinical outcome.[9] Usually, lavage is recommended for patients who developed significant toxicity requiring endotracheal intubation and who presented after relatively recent ingestion (several hours).
    • Activated charcoal reduces the absorption of CAs. It may also be beneficial in cases of multisubstance ingestion. It should be administered only in patients who are able to protect the airway.
  • Endotracheal intubation is indicated if the patient cannot adequately maintain a safe airway.
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Contributor Information and Disclosures
Author

Vivian Tsai, MD, MPH  Assistant Professor at Mount Sinai School of Medicine, Queens Hospital Center

Vivian Tsai, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Coauthor(s)

Mark A Silverberg, MD, FACEP, MMB  Assistant Professor, Assistant Residency Director, Department of Emergency Medicine, State University of New York Downstate College of Medicine; Consulting Staff, Department of Emergency Medicine, Staten Island University Hospital, Kings County Hospital, University Hospital, State University of New York Downstate at Brooklyn

Mark A Silverberg, MD, FACEP, MMB is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, Council of Emergency Medicine Residency Directors, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Mark Biittner, MD  Consulting Staff, Department of Emergency Medicine, Sutter Roseville Medical Center

Mark Biittner, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

Specialty Editor Board

Miguel C Fernandez, MD, FAAEM, FACEP, FACMT, FACCT  Associate Clinical Professor, Department of Surgery/Emergency Medicine and Toxicology, University of Texas School of Medicine at San Antonio; Medical and Managing Director, South Texas Poison Center

Miguel C Fernandez, MD, FAAEM, FACEP, FACMT, FACCT is a member of the following medical societies: American Academy of Emergency Medicine, American College of Clinical Toxicologists, American College of Emergency Physicians, American College of Medical Toxicology, American College of Occupational and Environmental Medicine, Society for Academic Emergency Medicine, and Texas Medical Association

Disclosure: Nothing to disclose.

John T VanDeVoort, PharmD  Regional Director of Pharmacy, Sacred Heart and St Joseph's Hospitals

John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists

Disclosure: Nothing to disclose.

John G Benitez, MD, MPH  Associate Professor, Department of Medicine, Medical Toxicology, Vanderbilt University Medical Center; Managing Director, Tennessee Poison Center

John G Benitez, MD, MPH is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, American College of Medical Toxicology, American College of Preventive Medicine, Society for Academic Emergency Medicine, Undersea and Hyperbaric Medical Society, and Wilderness Medical Society

Disclosure: Nothing to disclose.

John D Halamka, MD, MS  Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center

John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Asim Tarabar, MD  Assistant Professor, Director, Medical Toxicology, Department of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital

Disclosure: Nothing to disclose.

References

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