Cyclic antidepressant overdose: a review of current management strategies

Is there a Role for Hemoperfusion/Hemodialysis as a Treatment Option in Severe Tricyclic Antidepressant Intoxication?

Objective

Suicidal self-poisoning with tricyclic antidepressants like doxepin is a major therapeutic problem in emergency medicine with a high fatality rate. Deaths are mainly caused by cardiotoxicity with arrhythmias, intraventricular conduction disturbances and myocardial depression. For treatment, alkalinization and hypertonic saline are recommended. The role of extracorporeal treatment procedures is not clear. The possible benefit of hemoperfusion/hemodialysis is discussed in a case report with respect to the published literature.

Case Report

After ingestion of an amount of at least 5000 mg doxepin a 37-year-old man with endogenous depression developed cardiac arrest. After preclinical resuscitation with prolonged external cardiac massage, he was admitted to the intensive care unit with persistently severe hypotension and wide QRS complexes (230–260 ms). Despite fluid load, alkalinization, hypertonic saline and high-dose vasoactive substances the patient's condition did not improve. Hemoperfusion over hemoresin combined with hemodialysis led to an impressive clinical improvement with shortening of QRS duration (from 230 to 120 ms) and hemodynamic stabilization. The patient fully recovered without neurologic deficits.

Conclusion

We report a successful treatment with hemoperfusion over hemoresin and hemodialysis in a patient with life-threatening doxepin poisoning intractable with the generally recommended treatment. In such acute TCA intoxication with severe cardiotoxicity, hemoperfusion/hemodialysis should be considered a potential treatment option, as the “toxicokinetics” of drugs may totally differ from their usual pharmacokinetic behaviour. Experimental and clinical studies are needed to clarify the toxicokinetics of TCA in order to improve the therapeutic approach.

Toxicologic emergencies in the intensive care unit: management using reversal agents and antidotes

PURPOSE

To review the most common drugs implicated in overdoses admitted to the intensive care unit focusing on antidotes and reversal agents used in their management.

SUMMARY

Poisonings and overdoses due to pharmaceutical agents result in more than 100 000 critical care unit admissions each year. Ingestion of toxic alcohols, calcium channel blockers, beta-adrenergic antagonists, benzodiazepines, opioids, acetaminophen, tricyclic antidepressants, and salicylates are associated with a high rate of morbidity and mortality. Reviewing the mechanism of toxicity due to specific agents along with the mechanism of action, dosing, and adverse effects of appropriate antidotes is important for the successful management of these patients within the critical care unit.

CONCLUSION

Understanding the most prevalent overdoses and their management using reversal agents and antidotes is essential to the overall treatment of these critically ill patients.

Tricyclic antidepressant poisoning: an evidence-based consensus guideline for out-of-hospital management

A review of U.S. poison center data for 2004 showed over 12,000 exposures to tricyclic antidepressants (TCAs). A guideline that determines the conditions for emergency department referral and prehospital care could potentially optimize patient outcome, avoid unnecessary emergency department visits, reduce healthcare costs, and reduce life disruption for patients and caregivers. An evidence-based expert consensus process was used to create the guideline. Relevant articles were abstracted by a trained physician researcher. The first draft of the guideline was created by the lead author. The entire panel discussed and refined the guideline before distribution to secondary reviewers for comment. The panel then made changes based on the secondary review comments. The objective of this guideline is to assist poison center personnel in the appropriate prehospital triage and management of patients with suspected ingestions of TCAs by 1) describing the manner in which an ingestion of a TCA might be managed, 2) identifying the key decision elements in managing cases of TCA ingestion, 3) providing clear and practical recommendations that reflect the current state of knowledge, and 4) identifying needs for research. This guideline applies to ingestion of TCAs alone. Co-ingestion of additional substances could require different referral and management recommendations depending on their combined toxicities. This guideline is based on the assessment of current scientific and clinical information. The panel recognizes that specific patient care decisions may be at variance with this guideline and are the prerogative of the patient and the health professionals providing care, considering all the circumstances involved. This guideline does not substitute for clinical judgment. Recommendations are in chronological order of likely clinical use. The grade of recommendation is in parentheses. 1) Patients with suspected self-harm or who are the victims of malicious administration of a TCA should be referred to an emergency department immediately (Grade D). 2) Patients with acute TCA ingestions who are less than 6 years of age and other patients without evidence of self-harm should have further evaluation including standard history taking and determination of the presence of co-ingestants (especially other psychopharmaceutical agents) and underlying exacerbating conditions, such as convulsions or cardiac arrhythmias. Ingestion of a TCA in combination with other drugs might warrant referral to an emergency department. The ingestion of a TCA by a patient with significant underlying cardiovascular or neurological disease should cause referral to an emergency department at a lower dose than for other individuals. Because of the potential severity of TCA poisoning, transportation by EMS, with close monitoring of clinical status and vital signs en route, should be considered (Grade D). 3) Patients who are symptomatic (e.g., weak, drowsy, dizzy, tremulous, palpitations) after a TCA ingestion should be referred to an emergency department (Grade B). 4) Ingestion of either of the following amounts (whichever is lower) would warrant consideration of referral to an emergency department: an amount that exceeds the usual maximum single therapeutic dose or an amount equal to or greater than the lowest reported toxic dose. For all TCAs except desipramine, nortriptyline, trimipramine, and protriptyline, this dose is >5 mg/kg. For despiramine it is >2.5 mg/kg; for nortriptyline it is >2.5 mg/kg; for trimipramine it is >2.5 mg/kg; and for protriptyline it is >1 mg/kg. This recommendation applies to both patients who are naïve to the specific TCA and to patients currently taking cyclic antidepressants who take extra doses, in which case the extra doses should be added to the daily dose taken and then compared to the threshold dose for referral to an emergency department (Grades B/C). 5) Do not induce emesis (Grade D). 6) The risk-to-benefit ratio of prehospital activated charcoal for gastrointestinal decontamination in TCA poisoning is unknown. Prehospital activated charcoal administration, if available, should only be carried out by health professionals and only if no contraindications are present. Do not delay transportation in order to administer activated charcoal (Grades B/D). 7) For unintentional poisonings, asymptomatic patients are unlikely to develop symptoms if the interval between the ingestion and the initial call to a poison center is greater than 6 hours. These patients do not need referral to an emergency department facility (Grade C). 8) Follow-up calls to determine the outcome for a TCA ingestions ideally should be made within 4 hours of the initial call to a poison center and then at appropriate intervals thereafter based on the clinical judgment of the poison center staff (Grade D). 9) An ECG or rhythm strip, if available, should be checked during the prehospital assessment of a TCA overdose patient. A wide-complex arrhythmia with a QRS duration longer than 100 msec is an indicator that the patient should be immediately stabilized, given sodium bicarbonate if there is a protocol for its use, and transported to an emergency department (Grade B). 10) Symptomatic patients with TCA poisoning might require prehospital interventions, such as intravenous fluids, cardiovascular agents, and respiratory support, in accordance with standard ACLS guidelines (Grade D). 11) Administration of sodium bicarbonate might be beneficial for patients with severe or life-threatening TCA toxicity if there is a prehospital protocol for its use (Grades B/D). 12) For TCA-associated convulsions, benzodiazepines are recommended (Grade D). 13) Flumazenil is not recommended for patients with TCA poisoning (Grade D).

Do Adenosine Receptors Play a Role in Amitriptyline‐Induced Cardiovascular Toxicity in Rats?

OBJECTIVE

The aim of the our study was to investigate the role of adenosine receptors on cardiovascular toxicity induced by amitriptyline, a tricyclic antidepressant agent. Therefore, the hypothesis of this study was that adenosine receptor antagonists would improve and/or prevent amitriptyline-induced hypotension and conduction abnormalities in an anesthetized rat model of amitriptyline intoxication.

METHODS

Two separate experimental protocols were performed. Amitriptyline intoxication was induced by the infusion of amitriptyline 0.94 mg/kg/min until 40-45% reduction of mean arterial pressure (MAP). Sodium cromoglycate (10 mg/kg) was injected i.v. to inhibit the A3 receptor-mediated activation of mast cells. In protocol 1, after amitriptyline infusion, while control animals (n=8) were given dextrose solution, treatment groups received a selective adenosine A1 antagonist DPCPX (8-cyclopentyl-1,3-Dipropylxanthine, 20 microg/kg/min, n=8) or a selective A2a antagonist CSC (8-(3-chlorostyryl) caffeine, 24 microg/kg/min, n=8) for 60 minutes. In protocol 2, after the sodium cromoglycate, while control group of rats (n=8) recevied a dextrose solution, treatment groups of rats were administered DPCPX (20 microg/kg/min, n=8) or CSC (24 microg/kg/min, n=8) infusion to block adenosine A1 and A2a receptors for 20 minutes before amitriptyline infusion. After pretreatment with adenosine antagonists, all rats were given a dose of 0.94 mg/kg/min of amitriptyline infusion during 60 minutes. Outcome measures were mean arterial pressure (MAP), heart rate (HR), QRS duration and survival rate.

RESULTS

In protocol 1, amitriptyline infusion significantly reduced MAP and prolonged QRS within 15 minutes. HR was not changed significantly during the experiments. While dextrose did not improve MAP and QRS prolongation, DPCPX or CSC administration developed a significant improvement in MAP compared to the dextrose group within 10 min (88.5 +/- 2.8%, 75.6 +/- 4.7% and 50.1 +/- 14.7%, p<0.01, p<0.05, respectively). Both DPCPX and CSC decreased QRS prolongation (p<0.05) and increased median survival time significantly (log-rank test, p<0.00001). In protocol 2, pretreatment with DPCPX or CSC prevented the reduction in MAP due to amitriptyline toxicity compared to rats administered dextrose infusion (99.5 +/- 2.6%, 102.4 +/- 2.6%, 81.8 +/- 5.4, p<0.01 at 30 min; 98.0 +/- 2.9%, 93.5 +/- 6.0%, 64.9 +/- 4.7, p<0.001, p<0.01 at 40 min, respectively). Pretreatment with DPCPX or CSC also prevented the QRS prolongation (p<0.05) and increased median survival time significantly (log-rank test, p<0.0001).

CONCLUSION

Adenosine antagonists were found to be effective in improving hypotension, QRS prolongation and survival time in our rat model of amitriptyline toxicity. Additionally, amitriptyline-induced cardiotoxicity was abolished by pretreatment with adenosine receptor antagonists. These results suggest that adenosine receptors may have a role in the pathophysiology of amitriptyline-induced cardiovascular toxicity. Adenosine A1 and A2a receptor antagonists may be promising agents for reversing amitriptyline-induced cardiovascular toxicity.

Review of prehospital sodium bicarbonate use for cyclic antidepressant overdose

OBJECTIVE

To describe the clinical presentation of patients with cyclic antidepressant (CA) and use of sodium bicarbonate (NaHCO(3)) in the treatment of this overdose in the prehospital setting.

METHODS

A three year retrospective observational review of records was performed using the San Diego County Quality Assurance Network database for prehospital providers. All adult patients who were treated with NaHCO(3) by paramedics for a CA overdose were included. Demographic data, presenting cardiovascular and neurological symptoms, paramedic treatments, and any changes in status were reviewed.

RESULTS

Twenty one patients were treated by paramedics with NaHCO(3) for CA overdose. Seventeen patients (80%) presented with mental status changes, including 11 presenting with a GCS<8. Seven of the 21 (33%) presented with a cardiac arrhythmia expected to possibly respond to NaHCO(3) treatment. Seven of the 21 (33%) were hypotensive, and five (24%) patients had reported seizure activity. Only 2 of the 21 patients (10%) treated with NaHCO(3) had recorded improvements after administration of the drug, while the other 19 remained stable without any deterioration. Sixteen of 21 patients (76%) were given NaHCO(3) for indications on standing order, while five patients were treated outside the standing order indications by base physician order with none of the five patients having any change in status ater treatment.

CONCLUSIONS

After prehospital NaHCO(3) use in patients with CA overdose, there were no complications reported, two patients improved in status and the others remained unchanged. Base hospital physician orders of NaHCO(3) for indications beyond the standing orders were not associated with changes in patient status.

Extracorporeal therapies for acute intoxications

Intoxications frequently perturb acid-base and electrolyte status, intravascular volume, and renal function. In selected cases, extracorporeal techniques effectively restore homeostasis and augment intoxicant removal. The use of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, is a new and effective treatment for patients exposed to toxic alcohols. In this section, practical approaches to commonly encountered intoxicants and the use of extracorporeal techniques are critically reviewed.

Serial electrocardiographic changes as a predictor of cardiovascular toxicity in acute tricyclic antidepressant overdose

Tricyclic antidepressant agents continue to be a leading cause of significant morbidity and mortality in reported poisonings involving pharmaceutical agents. Although the history and physical examination play an important role in the assessment of patients with tricyclic antidepressant overdose, the presence of anticholinergic features on examination cannot predict the severity of the overdose. Several clinical variables, in particular electrocardiographic (ECG) changes, have been proposed as a guide to determine the severity of the tricyclic antidepressant poisoning. The authors describe a patient with tricyclic antidepressant overdose who presented with altered mental status and whose serial ECG changes played a significant role in diagnosing and predicting the impending cardiovascular toxicity. The role of ECG changes in making the diagnosis and assessing the severity of the tricyclic antidepressant overdose is reviewed.

ECG abnormalities in tricyclic antidepressant ingestion

The tricyclic antidepressant (TCA) agents are recognized for their potentially lethal cardiovascular and neurological effects in poisoned patients. The 12-lead electrocardiogram (ECG) has emerged as a popular bedside tool in the evaluation of TCA toxicity. Although the history and physical examination play a key role in the assessment of the patient with potential TCA poisoning, the presence or absence of features of the TCA toxidrome are not sufficient to detect or exclude toxicity from this class of drugs. A variety of ECG findings occur with TCA toxicity. Aside from the sinus tachycardia due principally to anticholinergic effects, TCA-toxic changes seen on the ECG are attributable primarily to the sodium channel blockade caused by these agents. The majority of patients at significant risk for developing cardiac or neurological toxicity will have a QRS complex greater than 0.10 seconds or a rightward shift of the terminal 40 ms of the frontal plane QRS complex vector. The majority of these patients will also display these changes early in their emergency department stay. However, the appearance of these findings, either alone or in combination, does not mean the patient will develop significant cardiac or neurological toxicity. The ECG can neither unequivocally rule in nor rule out impending toxicity; recognizing these limitations, the emergency physician can use this bedside tool in combination with other clinical data during the assessment of the poisoned patient.

Life-threatening dysrhythmias in severe thioridazine poisoning treated with physostigmine and transient atrial pacing

OBJECTIVES

To describe clinical, electrocardiographic, and blood chemistry findings in a case of high-dosage thioridazine self-poisoning, focusing on the cellular mechanisms of the cardiovascular toxicity.

DESIGN

Case report and literature review.

SETTING

Intensive care unit (ICU) of a district hospital in Germany.

PATIENT

A 68-yr-old male patient admitted to the ICU for treatment of a severe thioridazine intoxication.

INTERVENTIONS

Prevention of absorption (gastric lavage), mechanical ventilation, fluids, alkalinization, catecholamines, drugs (physostigmine, neostigmine), direct current cardioversion/defibrillation, and transient pacemaker (atrial stimulation).

MEASUREMENTS AND MAIN RESULTS

Central nervous, cardiovascular, and gastrointestinal systems indicated the adverse side effects of thioridazine intoxication over a period of 9 days. During high toxic thioridazine plasma concentrations (6061 to 6480 ng/mL), a life-threatening crisis occurred due to malignant ventricular arrhythmias followed by bradycardia (e.g., sinus node arrest). The electrocardiogram showed delays in all parts of the conduction system of the heart, including prolonged repolarization for several days, which disappeared completely when thioridazine plasma concentrations were within the therapeutic range.

CONCLUSIONS

An individual therapeutic approach is needed in cases of thioridazine overdose. The primary aim is to stabilize the cardiac rhythm and the circulation.

Approach to the poisoned patient

Routine poison management involves the following: (1) stabilization, (2) toxidrome recognition, (3) decontamination, (4) antidote administration, (5) enhanced elimination of toxin, and (6) supportive care. Stabilization involves airway, ventilation, and circulation support. In the patient with altered mental status, oxygen, naloxone, glucose, and thiamine should be administered. Symptom complexes that relate to specific classifications of toxins are referred to as toxidromes. Emesis by means of syrup of ipecac is rarely used for in-hospital gastric decontamination. Activated charcoal is a useful adsorbent for gastric decontamination. Whole bowel irrigation is useful for iron, lead, and lithium poisoning and for the body packer phenomenon. Enhancement of elimination may involve multiple doses of activated charcoal, hemodialysis, or charcoal hemoperfusion.

Intentional drug overdose: predictors of clinical course in the intensive care unit

OBJECTIVE

To examine the characteristics of patients admitted to the Medical Intensive Care Unit (MICU) after intentional drug overdose.

DESIGN

Retrospective chart review, descriptive.

SETTING

Midwestern teaching hospital.

SUBJECTS

Convenience sample of 43 patients admitted to the MICU after intentional drug overdose.

OUTCOME MEASURES

Survival and disposition of those patients who survived and were discharged from the MICU.

RESULTS

Ninety-five percent of the patients survived and were discharged from the MICU; Acute Physiology and Chronic Health Evaluation II scores ranged from 1 to 29 (mean, 8); Glascow Coma Scale scores ranged from 3 to 15 (mean 12.5); five patients were intubated and two patients had serious electrocardiograph changes requiring pharmacologic intervention for dysrhythmia.

CONCLUSIONS

Neurologic findings were the best indicators of serious complications after drug overdose. THerefore, patients with a Glascow Coma Scale score of more than six, and who are not intubated, may not need admission to an intensive care unit.