Incidence of late arrhythmias following tricyclic antidepressant overdose

Amitriptyline-induced ventricular tachycardia: a case report

Background

In Bangladesh, each emergency physician faces amitriptyline overdose nearly a day. An acute cardiovascular complication, one of the worst complications is mainly responsible for the mortality in tricyclic overdose. Recently, we managed ventricular tachycardia in a young female presented with an impaired consciousness 10 h after intentionally ingesting 2500 mg amitriptyline. Here, we report it, discuss how the electrocardiography is vital to acknowledge and predict it and its’ complications and also the recent update of the management of it.

Case presentation

A young married Bangladeshi-Bengali girl, 25-year-old, having a history of disharmony with her husband, came with an impaired consciousness after intentionally ingesting 2500 mg amitriptyline about 10 h before arrival. There was blood pressure 140/80 mmHg, heart rate 140 beats-per-min, temperature 103 °F, Glasgow coma scale 10/15, wide complex tachycardia with QRS duration of 178 ms in electrocardiography, blood pH 7.36. Initially, treated with 100 ml 8.4% sodium bicarbonate. After that, QRS duration came to 100 ms in electrocardiography within 10 min of infusion. To maintain the pH 7.50–7.55 over the next 24 h, the infusion of 8.4% sodium bicarbonate consisting of 125 ml dissolved in 375 ml normal saline was started and titrated according to the arterial blood gas analysis. Hence, a total dose of 600 mmol sodium bicarbonate was given over next 24 h. In addition to this, gave a 500 ml intravenous lipid emulsion over 2 h after 24 h of admission as she did not regain her consciousness completely. Afterward, she became conscious, though, in electrocardiography, ST/T wave abnormality persisted. So that, we tapered sodium bicarbonate infusion slowly and stopped it later. At the time of discharge, she was by heart rate 124/min, QRS duration 90 ms in electrocardiogram along with other normal vital signs.

Conclusion

Diagnosis of amitriptyline-induced ventricular tachycardia is difficult when there is no history of an overdose obtained. Nevertheless, it should be performed in the clinical background and classic electrocardiographic changes and wise utilization of sodium bicarbonate, intravenous lipid emulsion, and anti-arrhythmic drugs may save a life.

Tricyclic Antidepressants in the Intensive Care Unit

Tricyclic antidepressants (TCAs) are one of the most commonly prescribed classes of antidepressant medica tions, and they may account for more than 25% of all serious drug overdoses for persons admitted to adult intensive care units (ICUs). TCA overdose is the most common life-threatening drug ingestion in the United States, with an in-hospital mortality ranging from 0.6 to 15%. Manifestations of a significant overdose include anticholinergic effects (fever, mydriasis, tachycardia, and urinary retention), central nervous system toxicity (confusion, agitation, coma, hallucinations, and grand mal seizures), respiratory depression, and cardiovascu lar toxicity (ventricular tachycardia or fibrillation, hypotension, and conduction defects). The principal cardiovascular findings associated with therapeutic doses of TCAs are discussed and grouped into three categories: (1) electrocardiographic changes—sinus tachycardia, repolarization abnormalities, conduction disturbances, and ventricular arrhythmias; (2) mild depression of myocardial contractility; and (3) sudden cardiac death. The therapeutic feasibility and selection of a TCA for patients with preexisting cardiovascular disease is discussed, and current recommendations on the diagnosis and management of TCA overdoses are reviewed.

Clinical aspects of tricyclic antidepressant poisoning

Self-poisoning with antidepressant drugs was studied retrospectively in 225 patients admitted to an intensive care unit. Amitriptyline accounted for the overwhelming majority of cases (70%); 106 patients (47%) had taken two or more drugs, in 81 patients (36%) ethanol was found in the blood. Four patients (2%) died. On admission, 111 patients (49%) were unconscious (grade III). A further 30 patients (13%) were in grade IV coma, and of these 27 had taken amitriptyline. Twenty-four hours after admission, 22 patients (10%) remained in coma. Thirty-six patients (16%) required assisted ventilation. Nineteen patients (8%) had convulsions and 6 (3%) aspired stomach contents. Sixty-one patients (27%) had a widened QRS interval exceeding 100 msec, 18 (30%) of them required assisted ventilation, 21 (34%) were in stage IV coma and 15 (25%) had convulsions. This relationship between a widened QRS interval and the severity of intoxication should be considered in the initial assessment of patients with tricyclic antidepressant poisoning.

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).

Tricyclic antidepressant poisoning : cardiovascular toxicity

Tricyclic antidepressants remain a common cause of fatal drug poisoning as a result of their cardiovascular toxicity manifested by ECG abnormalities, arrhythmias and hypotension. Dosulepin and amitriptyline appear to be particularly toxic in overdose. The principal mechanism of toxicity is cardiac sodium channel blockade, which increases the duration of the cardiac action potential and refractory period and delays atrioventricular conduction. Electrocardiographic changes include prolongation of the PR, QRS and QT intervals, nonspecific ST segment and T wave changes, atrioventricular block, right axis deviation of the terminal 40 ms vector of the QRS complex in the frontal plane (T 40 ms axis) and the Brugada pattern (downsloping ST segment elevation in leads V1-V3 in association with right bundle branch block). Maximal changes in the QRS duration and the T 40 ms axis are usually present within 12 hours of ingestion but may take up to a week to resolve. Sinus tachycardia is the most common arrhythmia due to anticholinergic activity and inhibition of norepinephrine uptake by tricyclic antidepressants but bradyarrhythmias (due to atrioventricular block) and tachyarrhythmias (supraventricular and ventricular) may occur. Torsade de pointes occurs uncommonly. Hypotension results from a combination of reduced myocardial contractility and reduced systemic vascular resistance due to alpha-adrenergic blockade. Life-threatening arrhythmias and death due to tricyclic antidepressant poisoning usually occurs within 24 hours of ingestion. Rapid deterioration is common. Level of consciousness at presentation is the most sensitive clinical predictor of serious complications. Although a QRS duration >100 ms and a rightward T 40 ms axis appear to be better predictors of cardiovascular toxicity than the plasma tricyclic drug concentration, they have at best moderate sensitivity and specificity for predicting complications.

A Meta‐Analysis of Prognostic Indicators to Predict Seizures, Arrhythmias or Death After Tricyclic Antidepressant Overdose

OBJECTIVES

To systematically review and summarize studies on the accuracy of ECG and tricyclic antidepressant (TCA) concentration as prognostic indicators of the risk of seizures, ventricular arrhythmia (VA) or death in patients with TCA overdose.

METHODS

Articles were identified with MedLine and Cochrane register of controlled clinical trials searches and review of medical toxicology textbooks. Quality of the included studies was assessed. Pooled estimates of sensitivity, specificity, likelihood ratios and Summary Receiver Operating Characteristics (SROC) curves were generated.

RESULTS

A total of 18 studies were included in the analysis. The pooled sensitivity (Se) and specificity (Sp) of the QRS for predicting seizures were 0.69 [95% CI 0.57-0.78] and 0.69 [95% CI 0.58-0.78] as compared to 0.75 [95% CI 0.61-0.85] and 0.72 [95% CI 0.61-0.81] for the TCA concentration. The Se and Sp of the QRS to predict VA were 0.79 [95% CI 0.58-0.91] and 0.46 [95% CI 0.35-0.59] compared to 0.78 [95% CI 0.56-0.90] and 0.57 [95% CI 0.46-0.67] for the TCA concentration. The Se and Sp of the QRS to predict death were 0.81 [95% CI 0.54-0.94] and 0.62 [95% CI 0.55-0.68] compared to 0.76 [95% CI 0.49-0.91] and 0.60 [95% CI 0.47-0.72] for the TCA concentration. Very few studies evaluated the accuracy of QTc, T 40 ms axis and the R/S ratio.

CONCLUSIONS

Overall, the studies suggested that the ECG and TCA concentration have similar but relatively poor performance for predicting complications, such as seizures, VA or death, associated with TCA overdose.

Treatment of severe tricyclic antidepressant overdose with extracorporeal sorbent detoxification

Tricyclic overdose can be a medical emergency, and therapy with intravenous bicarbonate is not always successful in preventing cardiac toxicity or coma. Mortality in patients developing these complications is from 1% to 15%. Extracorporeal detoxification with sorbents has been used in treatment of patients with very high drug levels and declining clinical condition. Ten patients with serious drug overdose caused by tricyclics failed to respond quickly to standard therapy and were in stage 3-4 encephalopathy. Nine of these patients were on respirator support, 5 had hypotension, and 6 had QRS widening. Average level was 1,423 microg/L at presentation. Enteral activated charcoal and intravenous (IV) bicarbonate were initiated in the emergency room. The patients were treated for 3 to 4 hours with the Liver Dialysis Unit, a hemodiabsorption device using a cellulosic plate dialyzer and sorbent suspension as dialysate. Inflow and outflow blood levels indicated that the hemodetoxifier removed modest amounts of the tricyclics, metabolites, and other consumed drugs. The clinical improvement of the patients was dramatic, with patients reaching stage 0 or 1 encephalopathy during the treatment. Ventilator support was removed at the end of treatment for 3 patients who had not already developed pneumonia, and for others was prolonged up to 48 hours because of pneumonia, rather than mental status. Average length of stay in the intensive care unit (ICU) was 4.8 days (range 1 to 7 days). None of the patients died despite their high risk for ventricular arrhythmias, seizures, and death. Clinical improvement may have been attributable to removal of free drug from the blood or to removal of drug metabolites.

Tricyclic antidepressant overdose: a review

Overdoses of tricyclic antidepressants are among the commonest causes of drug poisoning seen in accident and emergency departments. This review discusses the pharmacokinetics, clinical presentation and treatment of tricyclic overdose.

Selected tricyclic antidepressant ingestions involving children 6 years old or less

OBJECTIVE

According to the annual report of the American Association of Poison Control Centers, tricyclic antidepressant (TCA) ingestions accounted for 15,708 exposures in 1998, of which 70% (all age groups) were treated at health care facilities (HCFs), with an estimated 2,022 children less than 6 years of age exposed. The study objective was to evaluate the manifestations, referral patterns, HCF management, and medical outcomes in pediatric patients 6 years old or less with TCA ingestions reported to a regional poison control center.

METHODS

All TCA (amitriptyline, clomipramine, desipramine, doxepin, imipramine, nortriptyline) ingestions from January 1, 1993, to December 31, 1997, involving patients aged 6 years or less managed by the poison control center were evaluated for dose, symptoms, treatments, disposition, and outcome.

RESULTS

Forty-four of 48 patients (92%) were asymptomatic. All were single-drug exposures. Forty-three patients (90%) ingested a TCA dose that was less than the normally prescribed pediatric dose (5 mg/kg). Of the five children ingesting >5 mg/kg (range 5-9.4 mg/kg), only one (5.3 mg/kg) was mildly symptomatic (drowsy) prior to admission. Thirty-one of the 48 (65%) were sent to the emergency department (dose range 0.59-9.4 mg/kg). Fourteen of the 31 were admitted for 12-24-hour observation and none subsequently developed symptoms. Twenty-three (74%) received activated charcoal (AC). There was no difference in outcome between the children who did and did not receive AC.

CONCLUSIONS

No case of significant toxicity occurred in the children who experienced unintentional TCA ingestions in this study population. None of the children in the study had toxicity at doses <5 mg/kg. Further study is necessary to develop clinical guidelines for the appropriate referral of unintentional ingestions of TCA involving children.

Delayed toxidromes

Some toxins do not result in clinical manifestations until several hours after exposure. This article reviews those agents that may cause delayed-onset toxicity. They are organized into four classes: specific pharmaceuticals, biologicals, pharmaceutical dosage forms, and chemicals. There are five basic mechanisms for delayed toxicity: delayed absorption, distribution factors, metabolic factors, cellular and organ capacity effects, and unknown. Scientific evidence for delayed-onset of effects varies considerably among the individual toxins.

The etiology of cardiac arrest in children and young adults: special considerations for ED management

Children and young adults rarely present to the emergency department (ED) in cardiac arrest. This review examines published series on nontraumatic, cardiac arrest for patients aged 1 to 45 years and discusses the differential diagnosis for cardiovascular collapse. Among the most common entities encountered are cardiac diseases (hypertrophic cardiomyopathy, myocarditis), airway diseases (pneumonia, epiglottitis, and asthma), epilepsy, hemorrhage (gastrointestinal bleeding, ectopic pregnancy), and drug toxicity (tricyclic antidepressants, cocaine). ED management of children and young adults in cardiac arrest requires an understanding of the heterogeneous pathophysiologic mechanisms and etiologies leading to cardiopulmonary dysfunction in these patients. The emergency physician should give particular focus to airway management for toddlers and preadolescents, because respiratory diseases predominate. When treating an adolescent or young adult, the resuscitation team should also consider toxic causes as well as occult hemorrhage. Management considerations unique to this patient population are discussed.

Cardiovascular repercussions of seizures during cyclic antidepressant poisoning

Cyclic antidepressant overdose involves a risk of generalized seizures and cardiovascular disturbances. We have conducted a retrospective study to test the hypothesis of a relationship between generalized seizures and the onset of arrhythmia, hypotension or cardiac arrest during cyclic antidepressant intoxication. Patients who had seizures after ingestion of toxic amounts of tri- or tetracyclic antidepressants were included. Limb-lead QRS complex duration and systolic blood pressure were recorded before and after seizure. Twenty-four of the 388 patients (6.2%) who were admitted to our ICU over a four-year period had seizures (2.3 +/- 2 seizures/patient). Cardiac repercussions of cyclic-induced seizure were frequent and severe. In the postictal period, broadening of the QRS duration or hypotension occurred or were exacerbated in at least 41% and 29% of cases, respectively. In three patients (12.5%), the seizure-induced cardiovascular state was life-threatening and required massive alkalinization therapy and vasopressors, and two of the three required cardiac massage or cardioversion. Prior to seizure, these three patients had severe intoxications characterized by QRS duration > or = 120 ms and systolic blood pressure < or = 80 mm Hg. The results of this work confirm the potential risk of cardiovascular deterioration after cyclic antidepressant-induced seizure and raise the question of a prophylactic approach especially towards the subgroup with unstable hemodynamic status.

Cyclic antidepressant overdose: a review of current management strategies

Cyclic antidepressant (CA) overdose can produce life-threatening seizures, hypotension, and dysrhythmias. It accounts for up to half of all overdose-related adult intensive care unit admissions and is the leading cause of death from drug overdose in patients arriving at the emergency department alive. Several factors contribute to the significant morbidity and mortality associated with CA overdose. First, CAs are widely prescribed and are dispensed to patients at increased risk for attempting suicide. Second, drugs of this class generally have a low therapeutic toxic ratio. Third, in the majority of fatal cases, the patient dies before reaching a hospital. Finally, and of greatest significance for the clinician, the presenting signs and symptoms of CA overdose may be missed by the physician, even in cases of severe toxicity. Therefore, CAs must be considered early in any case of suspected overdose, and all such cases should be managed as potentially fatal ones. The following case demonstrates the current approach to the patient with significant CA toxicity.

Tricyclic antidepressant poisoning

OBJECTIVE

To review poisoning with tricyclic antidepressants.

DATA SOURCE

English language literature search using Australian Medlars Service (1977-1989), manual search of journals and review of bibliographies in identified articles.

STUDY SELECTION

Approximately 250 articles, abstracts and book chapters were selected for analysis.

DATA EXTRACTION

The literature was reviewed and 93 articles were selected as representative of important advances.

DATA SYNTHESIS

The major features of overdose are neurological, cardiac, respiratory and anticholinergic. Life-threatening complications develop within six hours of overdose or not at all. All patients seen within six hours of overdose should have their stomachs emptied. All patients should receive activated charcoal. Coma, convulsions, respiratory depression and hypotension are treated with standard resuscitation techniques and drugs. Treat patients with significant cardiotoxicity or cardiac arrest with alkalinisation by sodium bicarbonate or hyperventilation, aiming for an arterial pH of 7.45-7.55. Lignocaine is used for ventricular arrhythmias. Other antiarrhythmic drugs are contraindicated (Class 1A, Class 1C), potentially lethal (Class II), of no benefit (phenytoin) or of unproven efficacy (Class III and Class IV). Physostigmine has no role at all. Haemodialysis and haemoperfusion are of no benefit.

CONCLUSION

The death rate of those who reach hospital is 2%-3%. Most of these deaths are cardiac in origin, and are caused by direct depression of myocardial function rather than cardiac arrhythmias.

Drug-induced supraventricular tachycardia: a case report of fluoxetine

We report the occurrence of supraventricular tachycardia and hypotension in a 54-year-old woman after maintenance therapy with fluoxetine. Although cases of tachycardia and palpitations have been reported, supraventricular tachycardia and hypotension have not been directly attributed to fluoxetine.

Tricyclic antidepressant toxicosis

Accidental ingestions of TCAs by companion animals often occur. During the past 4 years, over 450 cases have been reported to the IAPIC. At least 7% of the animals that displayed clinical signs of toxicosis eventually died. Overdoses of TCAs adversely affect the cardiovascular, parasympathetic, and central nervous systems. The cardiovascular system is involved most seriously and ventricular arrhythmias with severe hypotension are believed to be the primary cause of death. Animals that ingest a potentially lethal dose (over 15 mg/kg) may die within 1 to 2 hours if appropriate treatment is not administered. Treatment involves the use of initial life-supportive measures (control of seizures, maintenance of an airway, ventilation, and so on), detoxification of the animal (enterogastric lavage, activated charcoal, etc.), and the intravenous use of sodium bicarbonate (2-3 mEq/kg) to control signs of acidosis, hypotension, tachycardia, bradycardia, and other cardiac conduction abnormalities. The animal must then be monitored closely for the return of the clinical signs and sodium bicarbonate therapy should be repeated as needed. In addition, to enhance removal of the TCAs from the gastrointestinal tract and, ultimately, from the body, activated charcoal should be repeated at 3-hour intervals until the animal is asymptomatic.

The cardiovascular effects of antidepressants

This monograph comprises a review of the cardiovascular effects of the various types of antidepressant drugs in clinical use. The frequency, severity and clinical importance of these effects are placed in perspective. Most antidepressants can cause changes in blood pressure. Both the tricyclic type (TCA) and the monoamine oxidase inhibitors (MAOIs) can produce postural hypotension which may be dose-limiting. In addition, the MAOIs may be associated with severe hypertension when amine-containing foods or medicines are ingested. It is unlikely that therapeutic doses of any available antidepressant drug could impair cardiac contractility. Typical TCAs can cause abnormalities of cardiac conduction and arrhythmias, but this affects less than 5% of patients, mostly to a clinically insignificant extent. Newer compounds such as lofepramine, mianserin, trazodone and viloxazine seem safer in this respect. Reports of an association between therapeutic use of TCAs and sudden death are far from convincing. Overdosage with the MAOIs, lithium and carbamazepine is dangerous but not common; overdose with a TCA is a major source of morbidity and mortality. Lofepramine, mianserin and trazodone are relatively safe in overdose. The use of various antidepressants in patients with hypertension, cardiac failure, angina pectoris, myocardial infarction, or cardiac arrhythmias is discussed and guidelines suggested for the selection and use of antidepressant medication.

Hypotension in severe tricyclic antidepressant overdose

Sixty four patients who presented to the emergency department following severe acute tricyclic antidepressant (TCA) overdose (defined as an antidepressant ingestion associated with a QRS interval greater than or equal to 0.10 seconds, TCA level greater than or equal to 500 ng/mL, or grade IV coma) were prospectively evaluated to determine the incidence of hypotension and the factors associated with its development. Among these patients, the mean antidepressant level was 1,094 ng/mL. The overall frequency of admission hypotension (systolic BP less than 95 mmHg) was 34% (22 of 64 patients). Using regression analysis, systolic BP showed poor correlation with TCA level (r = -.37) and maximal QRS interval (r = -.17) following severe TCA overdose. Using multivariate analysis with a logistic regression model, the influence of BP (as well as TCA level, QRS interval, and coingestion of another drug) was evaluated on four clinical outcomes: seizures, arrhythmias, aspiration pneumonia, and pulmonary edema. The occurrence of arrhythmias and pulmonary edema was significantly associated (inversely) with hypotension (P less than .01). Seizures and aspiration pneumonia were unrelated to admission BP. These results suggest that hypotension is common after severe TCA overdose and occurs independently of TCA level and prolongation of the QRS interval. Hypotension is strongly associated with the development of arrhythmias and pulmonary edema. Seizures and aspiration pneumonia may occur regardless of initial BP.

Amoxapine cardiotoxicity

Prolongation of the QRS interval, cardiopulmonary arrest, and death in a 31-year-old woman following an overdose of 2 g amoxapine, a tricyclic antidepressant, is reported. The patient's QRS interval prolonged to beyond 100 ms throughout hospitalization. Thirty-three hours after admission she suffered a bradycardiac-hypotensive event, followed by electromechanical dissociation and subsequent death. Cardiotoxicity has not been directly related to amoxapine; a 2-g acute ingestion is the lowest reported lethal dose.

Level of consciousness as a predictor of complications following tricyclic overdose

In order to determine whether patients at low risk for complications following tricyclic antidepressant (TCA) overdose can be identified, we analyzed the records of all admissions for TCA overdose from 1975 to 1985. Of the 92 patients reviewed, 37 had serious complications including hypoventilation, loss of protective airway reflexes, seizures, hypotension, hemodynamically significant arrhythmias, or death. Patients with complications had increased heart rate, depressed level of consciousness, depressed Glasgow Coma Scale, and prolonged QRS interval, as compared to patients without complications. All 37 patients with serious complications required intubation in the emergency department. A Glasgow Coma Scale of less than 8 was the most sensitive predictor of serious complications (sensitivity = .86; specificity = .89). This was significantly better than the QRS interval (QRS greater than or equal to 100 msec; sensitivity = 59; specificity = .76). We conclude that level of consciousness is a better predictor of risk of complications and need for ICU admission than the QRS interval. Patients who are responsive to verbal stimuli on leaving the ED are at very low risk of developing complications.

QRS interval in tricyclic antidepressant overdosage: inaccuracy as a toxicity indicator in emergency settings

Emergency department treatment and disposition of tricyclic antidepressant (TCA)-overdose patients remains a common and difficult problem. Various clinical findings have been proposed as toxicity indicators. To study the performance of QRS duration as a predictor of toxicity in our patient population, we retrospectively reviewed the cases of all patients presenting to our ED with TCA overdosage. The charts of 102 patients with quantitative or qualitative laboratory confirmation of TCA ingestion were reviewed for ED findings and hospital course with specific attention to the occurrence of ventricular arrhythmias (VAs) or seizures. The ED ECG revealed that 57 patients had a maximal 12-lead ECG QRS interval duration (QRS) of less than .10 seconds (Group 1). The remaining 45 patients had QRS greater than or equal to .10 seconds (Group 2). Three patients (5%) in Group 1 and three (6%) in Group 2 experienced VAs. Four patients (7%) in Group 1 and five (11%) in Group 2 experienced seizures. There was no significant difference in the rate of occurrence of VAs or seizures between the two groups. Of note was the fact that five of eight VAs and nine of 11 seizures occurred in the ED setting. We conclude that determination of QRS duration is not an accurate indicator of VA or seizure risk for all TCA-overdose populations. In particular, risk of toxic events during the emergency phase of TCA overdose does not appear to be indicated by evaluation of the QRS duration in the ED.

Pulmonary consequences of severe tricyclic antidepressant ingestion

We prospectively studied 56 consecutive patients with severe tricyclic antidepressant ingestion to determine the incidence of associated pulmonary complications. Among the patients meeting the entrance criteria, the mean antidepressant level was 1136 ng/ml. Other characteristics were a QRS duration of greater than or equal to 0.1 seconds in 35 (63%) and seizures in 19 (34%). Seventeen patients (30%) developed 18 abnormal chest X-ray findings which included pulmonary edema in 8 cases and aspiration pneumonia in 10. Using logistic regression, we evaluated the influence of tricyclic antidepressant level, blood pressure, QRS interval, seizures, drug co-ingestion and the use of gastric lavage vs. ipecac-induced emesis on pulmonary complications. For patients with pulmonary edema, the only significantly associated factor was hypotension on emergency department presentation. For aspiration pneumonia, no significant associations were found. Co-ingestion of another drug had no apparent influence on the development of pulmonary abnormalities. Our findings suggest that pulmonary edema and aspiration pneumonia are frequent complications of severe ingestions of tricyclic antidepressants. Pulmonary edema appears to result from hypotension or its treatment. The etiology of aspiration pneumonia is unclear. A chest X-ray should be obtained in all victims of tricyclic antidepressant overdose.

Tricyclic antidepressant overdose: emergency department findings as predictors of clinical course

There is controversy regarding the appropriate utilization of health care resources in the management of tricyclic antidepressant overdosage. Antidepressant overdose patients presenting to the emergency department (ED) are routinely admitted to intensive care units, but only a small proportion develop cardiac arrhythmias or other complications requiring such an environment. The authors reviewed the findings in 165 patients presenting to an ED with antidepressant overdose. They found that major manifestations of toxicity on ED evaluation (altered mental status, seizures, arrhythmias, and conduction defects) were commonly associated with a complicated hospital course. Patients with the isolated findings of sinus tachycardia or QTc prolongation had no complications. No patient experienced a serious toxic event without major evidence of toxicity on ED evaluation and continued evidence of toxicity during the hospital course. These data support the concept that proper ED evaluation can identify a large body of patients with trivial ingestions who may not require hospital observation.

Poisoning due to tricyclic antidepressant overdosage. Clinical presentation and treatment

Tricyclic antidepressants are among the commonest causes of both non-fatal and fatal drug poisoning in the world. Their toxicity is due to effects on the brain, the heart, the respiratory system and the parasympathetic nervous system. Symptoms usually appear within 4 hours of an overdose and all but the most seriously poisoned patients recover within 24 hours. The most common clinical features are dry mouth, blurred vision, dilated pupils, sinus tachycardia, pyramidal neurological signs, and drowsiness. In severe poisoning, there may be coma, convulsions, respiratory depression, hypotension and a wide range of electrocardiographic (ECG) abnormalities. The most frequent findings on the ECG are prolongation of the PR and QT intervals; the tracing may resemble bundle branch block or supraventricular or ventricular tachycardias. Treatment of poisoning due to the tricyclic antidepressants is essentially supportive, there being insufficient evidence at present to recommend the use of methods to increase elimination of the drug from the body. Gastric aspiration and lavage should be performed if more than 750 mg of drug have been taken. There must be regular monitoring for hypoxia, acidosis and hypokalaemia and these complications should be corrected enthusiastically. Convulsions should be treated with diazepam or chlormethiazole. Muscular paralysis and artificial ventilation should be employed if anticonvulsants are ineffective. Hypotension should be treated firstly by fluid replacement and then with sympathomimetic agents (dopamine or dobutamine). Antiarrhythmic drugs should only be employed if there is evidence of circulatory failure which fails to respond to correction of hypotension. Sodium bicarbonate infusions should be given to cardiotoxic patients who are acidotic and are worth trying even if the patient is not acidotic. Although physostigmine salicylate will reverse most of the features of tricyclic antidepressant poisoning, its effects are short-lived in serious toxicity and it can produce dangerous side effects; physostigmine should therefore be reserved for those patients who have complications of coma or who have resistant cardiotoxicity or convulsions. Drug screening and quantitative determination of tricyclic antidepressant serum concentrations are useful in a minority of patients who have severe, unusual or prolonged symptoms.

Tricyclic antidepressant overdose

Overdose of a tricyclic antidepressant is a serious and all-too-frequent occurrence. The diagnosis must be considered in known or suspected overdoses, and signs such as a dry axilla, tachycardia, and wide QRS must be specifically sought. Management depends upon support of vital functions and a thorough understanding of the pharmacology of the drug. Emptying the gastrointestinal tract with ipecac or lavage and hastening elimination with activated charcoal and a cathartic are extremely important measures. Cardiac arrhythmias generally respond to sodium bicarbonate, and seizures respond to intravenous diazepam. Neither physostigmine nor dialysis are considered to be treatments of choice. As in other overdoses, counseling to prevent ingestions is more than worth "a pound of the cure."

The role of the laboratory in acute poisoning: case histories

We describe case histories and management of four patients poisoned with different compounds. The role of the laboratory, particularly of toxicological analysis, in the management of poisoned patients is examined.

Tricyclic antidepressant poisoning. Management of arrhythmias

Deaths from tricyclic antidepressant (TCA) overdose are usually due to arrhythmias and/or hypotension. Tricyclic antidepressant toxicity is due mainly to the quinidine-like actions of these drugs on cardiac tissues. Slowing of phase 0 depolarisation of the action potential results in slowing of conduction through the His-Purkinje system and myocardium. Slowed impulse conduction is responsible for QRS prolongation and atrioventricular block, and contributes to ventricular arrhythmias and hypotension. Therapies that improve conduction, e.g. hypertonic sodium bicarbonate, are useful in treating these toxic effects. Other mechanisms contributing to arrhythmias include abnormal repolarisation, impaired automaticity, cholinergic blockade and inhibition of neuronal catecholamine uptake. Toxicity may be worsened by acidaemia, hypotension or hyperthermia. Sinus tachycardia is due to the anticholinergic effects of the tricyclic antidepressants as well as blockade of neuronal catecholamine reuptake. Sinus tachycardia is generally well-tolerated and requires no therapy. Sinus tachycardia with QRS prolongation may be difficult to distinguish from ventricular tachycardia. Electrocardiograms obtained using oesophageal or atrial electrodes may be useful in determining the relationship of atrial and ventricular activity. Although QRS prolongation alone is not compromising, it is a marker for patients at highest risk of developing seizures, arrhythmias or hypotension. Ventricular tachycardia (monomorphic) is a consequence of impaired myocardial depolarisation and impulse conduction. Hypertonic sodium bicarbonate may partially correct impaired conduction and be of benefit in treating ventricular tachycardia. Since hypertonic sodium bicarbonate appears to act by increasing the extracellular sodium concentration as well as by increasing extracellular pH, hyperventilation may be less effective. Hypertonic sodium bicarbonate is of particular benefit in patients who are acidotic, since acidosis aggravates cardiac toxicity. However, administration of hypertonic sodium bicarbonate is beneficial even when blood pH is normal. Lignocaine (lidocaine) may be useful in treating ventricular tachycardia but should be administered cautiously to avoid precipitating seizures. Ventricular bradyarrhythmias are due to impaired automaticity or depressed atrioventricular conduction and can be treated by placement of a temporary pacemaker, or with a chronotropic agent, e.g. isoprenaline (isoproterenol), with or without concomitant vasoconstrictors.(ABSTRACT TRUNCATED AT 400 WORDS)

Epidemiology of fatal tricyclic antidepressant ingestion: implications for management

Although there is a large body of literature documenting the lethal cardiotoxic complications of tricyclic antidepressant (TCA) overdose, the absence of reliable predictive signs has led to a policy of admitting even trivial-appearing overdoses for inpatient observation. A study of 18 fatal cases revealed that with the exception of two that received clearly inadequate medical care, all fatal ingestions developed major signs of toxicity mandating admission within two hours of arrival at the hospital, and the mean time from arrival to death was only 5.43 hours. All patients who died of direct TCA toxicity did so within 24 hours of arrival. In addition, half the fatal cases presented with only trivial signs of poisoning, but deteriorated catastrophically within one hour. These data lead to an algorithm to guide admission of serious cases.

Arrhythmias in patients with drug toxicity, electrolyte, and endocrine disturbances

The common rhythm disturbances related to electrolyte imbalance are due predominantly to abnormalities of potassium. An understanding of the mechanism underlying these abnormalities is facilitated by a brief review of normal electrical activity during impulse propagation in cardiac tissue. Also discussed are the actions of all cardioactive and antiarrhythmic drugs on membrane permeability to ions. Lastly, the nonspecific arrhythmias associated with endocrine disturbances are outlined.