Demographic and electrocardiographic factors associated with severe tricyclic antidepressant toxicity

The role of QRS complex prolongation in predicting severe toxicity in single-xenobiotic overdose

OBJECTIVE

The QRS complex duration is commonly used to prognosticate severity, predict outcomes, and indicate treatment in overdose. However, literature to support this practice is mixed in tricyclic antidepressant overdoses and absent in non-tricyclic antidepressant overdoses. Our objective was to assess the validity of QRS complex duration as a prognostic marker in overdose.

METHODS

This was a secondary analysis of cases reported to the Toxicology Investigators Consortium between January 1, 2010, and December 31, 2022. Cases were assessed to determine the six xenobiotics most associated with QRS complex prolongation. All cases involving these six xenobiotics, regardless of QRS complex duration, constituted the study cohort. Inclusion criteria were cases of patients older than 12 years old with single-xenobiotic exposures. Clinical outcomes evaluated were seizure, ventricular dysrhythmia, metabolic acidosis, and death.

RESULTS

Of 94,939 total cases, diphenhydramine, amitriptyline, bupropion, quetiapine, nortriptyline, and cocaine were most associated with QRS complex prolongation. Inclusion criteria were met by 4,655 cases of exposure to these xenobiotics. QRS complex prolongation was associated with increased odds ratio of seizure in all included xenobiotics, of ventricular dysrhythmia in all included xenobiotics except nortriptyline, and of metabolic acidosis or death in all included xenobiotics except nortriptyline and quetiapine. A normal QRS complex duration had a negative predictive value of greater than or equal to 93.0 percent of developing metabolic acidosis and 98.0 percent of developing a ventricular dysrhythmia or death from the xenobiotics studied.

DISCUSSION

This study demonstrates that patients with QRS complex prolongation from all six xenobiotics studied had an increased prevalence and odds of developing severe outcomes. Furthermore, patients who did not develop QRS complex prolongation were unlikely to develop a ventricular dysrhythmia, metabolic acidosis, or death. These findings were noted in six xenobiotics that mechanistically can cause QRS complex prolongation through sodium channel or gap junction inhibition.

CONCLUSION

Identification of patients at risk for severe outcomes after overdose can be aided by measuring the QRS complex duration. If prospectively validated, these outcomes have implications on risk stratification, disposition level of care, and appropriateness of treatments.

Effect of intravenous midazolam on cardiac parameters in acute tricyclic antidepressants poisoning

BACKGROUND

Midazolam is commonly and safely used in poisoning management and intensive care for the control of agitated poisoned patients. Despite the introduction of newer and safer antidepressants, tricyclic antidepressants (TCAs) are still prescribed and used in many countries due to their cost-effectiveness. Severe morbidity and mortality associated with these drugs arises largely from their well-documented cardiovascular toxicity. In this study we aimed to investigate the probable effect of midazolam on some hemodynamic indices in TCAs-poisoned patients.

METHODS

In this clinical trial, we have evaluated some cardiovascular and hemodynamic indices of 100 TCAs-poisoned patients whom were randomly allocated for receiving midazolam with a first loading dose of 0.1 mg/kg (2 mg/minute) followed by a 6-hour maintenance infusion of 0.1 mg/kg/h of the drug in dextrose-saline (3.33% of dextrose and 0.33% of NaCl) or placebo (dextrose-saline infusion without midazolam). Pulse rate, systolic/diastolic blood pressure, respiratory rate, neurologic status and the outcome of therapy for all patients were recorded at the time of admission and hourly for the next 6 hours.

RESULTS

There was a statistically significant reduction in the heart rate of the midazolam treated group after the first hour of hospital admission. There were no significant differences in the respiratory rate, central nervous system manifestations and other indices between the two groups.

CONCLUSION

Midazolam may reduce tachycardia (and its fatal consequences) in the first hour of admission in TCAs-poisoned patients.

A retrospective analysis of antidepressant poisonings in the emergency department: 11-year experience

Between 1993 and 2004, patients with antidepressant poisoning admitted to an emergency department (ED) were analysed retrospectively with regard to demographics, clinical findings and treatment attempts. Age, gender, suicide attempts, classification of antidepressants, Glasgow Coma Scale (GCS) score, ECG findings, need for endotracheal intubation, follow-up period and Antidepressant Overdose Risk Assessment (ADORA) criteria were analysed by SPSS software. A total of 356 antidepressant poisoning cases were evaluated. Tricyclic antidepressants (TCA), especially opipramol and amitriptyline, were the most common agents (58.4%). The most frequent ECG finding was sinus tachycardia (40.7%, n=145). Endotracheal intubation was required in 9.6% of cases. Patients with TCA ingestion had a longer observation time in the ED, abnormal ECG findings, abnormal physical examination findings and more ADORA criteria, than patients who ingested selective serotonin re-uptake inhibitors (SSRI) (P=0.008, P=0.008, P<0.001, P<0.001). It was found that the patients who ingested TCA (P=0.001), poisoned with amitriptyline (P=0.001), patients with GCS scores of 8 and less (P=0.001), patients with two or more ADORA criteria (P=0.001), with seizures (P=0.001), with abnormal ECG (P=0.012), and patients with a history of two or more suicide attempts were intubated more frequently. Suicide attempts, classification of the antidepressant, ECG findings, seizure, GCS score and number of detected ADORA criteria affect the need for intubation in patients with antidepressant poisoning.

Acute amitriptyline intoxication: an analysis of 44 children

The tricyclic antidepressant agents, particularly amitriptyline and dothiepin, are recognized for their potentially lethal cardiovascular and neurological effects in poisoned patients. In this article, the clinical and laboratory findings of 44 children with amitriptyline intoxication are reviewed. Our purpose was to investigate amitriptyline intoxication in childhood. Of 44 patients, 21 (47.7%) were boys, 23 (52.3%) were girls, and the ages ranged from 12 months to 14 years (mean9 / SD; 4.099 / 2.9 years). All children except one who took an overdose of amitriptyline to decrease his pain accidentally ingested an overdose of amitriptyline. The amount of amitriptyline ingested was between 2 mg/kg and 97.5 mg/kg (mean9 / SD; 13.69 / 17.7 mg/kg per dose) (the drug dosage was not known in 13 children). The most commonly observed clinical and laboratory findings were lethargy, tachycardia, convulsion, hyperglycemia and leukocytosis. In all patients except for two children who died the abnormal clinical and laboratory findings returned to normal within a few days after admission and they were discharged from the hospital in good health within the fourth day of admission. One of the children ingested 97.5 mg/kg amitriptyline and probably died due to status epilepticus and another child who died ingested 36 mg/ kg amitriptyline and died due to cardiopulmonary arrest. In conclusion, our findings showed that initial symptoms and signs of acute amitriptyline intoxication appeared severe, but they disappeared with only supportive care required in most children except for cases that ingested high doses of drug within a few days. In contrast to adults, we infrequently noted respiratory insufficiency, arrhythmia and hypotension in children with acute amitriptyline intoxication.

Amitriptyline overdose in emergency department of university hospital: evaluation of 250 patients

OBJECTIVE

The purpose of this study was to evaluate the patients with acute amitriptyline poisoning and investigate predictive factors for the development of life-threatening complications.

METHODS

Demographics, clinical, laboratory, and electrocardiographic (ECG) findings of 250 patients were evaluated retrospectively. Predictive parameters for the development of serious complications were studied.

RESULTS

Median age of patients was 14.6 years, of which, 70% of patients were female and 66% were in pediatric age group. The most common pathological clinical finding and laboratory abnormality were alteration of consciousness and hyponatremia. The rate of convulsive seizure, arrhythmia, and respiratory depression were 17 (6.8%), 16 (6.4%), and 11 (4.4%), respectively. These complications were more seen in pediatric patients than adults (15.8% and 1.2%). The incidence of hyponatremia was more in pediatric patients and severe poisoning groups (38.8 and 53.4%, respectively). The levels of amitriptyline and nortriptyline were significantly higher in the group with complications than the group without complications (p < 0.05). All adult patients were discharged with good prognosis. In pediatric age group, one patient was discharged with severe neurological sequelae and one patient died. QRS duration >100 ms, long corrected QT duration interval, and low Glasgow Coma Score (GCS) at admission were identified as independent risk factors for the development of life-threatening complications (odds ratio: 69.4, 1.9, and 1383, respectively; p < 0.05).

CONCLUSION

Amitriptyline poisoning may be associated with life-threatening complications, especially in pediatric age group and in patients with hyponatremia. Low GCS, presence of hyponatremia, high serum drug levels, and pathological ECG findings on admission may be helpful in predicting the development of complications and poor prognosis.

Antidepressant overdose-induced seizures

Treating patients with psychiatric problems can present numerous challenges for clinicians. The deliberate self-ingestion of antidepressants is one such challenge frequently encountered in hospitals throughout the United States. This review focuses on 1) the classes of antidepressants, their pharmacologic properties, and some of the proposed mechanism(s) for antidepressant overdose-induced seizures; 2) the evidence for seizures caused by antidepressants in overdose; 3) management strategies for patients who have intentionally or unintentionally overdosed on an antidepressant, or who have experienced an antidepressant overdose-induced seizure.

Acute drug overdose: clinical profile, etiologic spectrum and determinants of duration of intensive medical treatment

OBJECTIVES

Acute drug overdosing is an important cause of organ dysfunction and metabolic derangements and the patients often require intensive care. This study aims to determine the clinical pattern of severe drug overdose as well as the factors influencing the duration of intensive care

METHODS

The clinical characteristics and course of consecutive adult patients admitted with a diagnosis of acute drug poisoning in the ICU of a tertiary hospital in Oman from January 2007 to December 2008 were reviewed retrospectively from the electronic case records.

RESULTS

Acute drug poisoning (n=29) constituted 3.9% of admissions to the ICU. Mean age was 29.38±7.9 years. They were brought in by their relatives (72%) or the state services (24%). Accidental poisoning was noted in 21 patients (72%) and suicidal overdosing in 6 (21%). The commonest drug was an opioid (65.5%). Glasgow Coma Scale score of ≤8 was recorded in 18 (62.1%). Sixty two percent of patients required mechanical ventilation. The prominent complications were hypotension in 9 (31%), pulmonary in 19 (65.5%), hepatic in 18 (62.1%) and renal in 12 (41.4%) patients. The major electrolytes abnormalities were low bicarbonate in 11 (37.9%), hyponatremia in 5 (17.2%) and hypokalemia in 4 (13.8%). Patients stayed in the ICU for 1 to 20 days (median-2 days). Factors associated with a longer ICU stay included hypotension upon arrival (p=0.048) and the need for mechanical ventilation on the first (p=0.001) and second (p=0.001) days of hospitalization. There was no mortality.

CONCLUSION

Early and prompt intensive medical therapy in acute drug poisoning can favorably influence the outcome. In addition, the presence of hypotension and requirement of mechanical ventilation on the first two days of hospitalization were responsible for prolonged ICU stay.

Is nurse interpretation of the ECG QRS width reliable?

Electrocardiogram (ECG) data are critical in formulating management strategies following sodium channel antagonist overdose. Poison centers frequently rely on verbal reports of the ECG obtained from bedside nurses. No previous study has addressed the quality of ECG data obtained in this manner. Therefore, we sought to test the ability of nurses to recognize and measure a widened QRS complex, the hallmark of myocardial sodium channel toxicity. Thirty-six emergency department and critical care nurses employed at a tertiary care hospital participated in this prospective study. The study subjects were divided into three groups and asked to interpret 12 ECGs (five normal and seven wide QRS). For each ECG, participants (1) determined if the QRS was narrow or wide and (2) measured the QRS duration. The groups differed in delivery of instruction regarding QRS measurement. Group 1 received visual instructions; group 2 received scripted verbal instructions, and group 3 served as controls, receiving no specific QRS measurement instructions. The nurse data was compared with physician interpretation (consensus of three physicians). Between-group analysis tested for impact of potential real-time educational intervention. Overall, the nurses identified a wide QRS complex most of the time (77%), but had difficulty in accurately measuring the QRS duration (44%). Real-time visual or verbal instruction did not improve accuracy (p = NS between groups). The results suggest that verbal ECG data from nurse callers is not sufficient to make an accurate clinical assessment in the setting of sodium channel poisoning.

Antidepressant overdose-induced seizures

Antidepressants are the most commonly prescribed class of medications in the United States. The clinician should be mindful of the many antidepressants that can produce seizures following an accidental exposure or an overdose. A broader understanding of the seizure potential of antidepressants, combined with the ability to recognize individuals at risk for a seizure after an overdose, can aid clinicians in determining the need for inpatient monitoring, and help facilitate their treatment decisions.

QTc intervals in drug poisoning patients with tricyclic antidepressants and selective serotonin reuptake inhibitors

Commonly used agents of drug poisoning among patients who come to the emergency services are tricyclic antidepressants (TCAs). These drugs may cause defect in cardiac conduction due to the slowdown in the cardiac depolarization and expansions in the QT interval. Selective serotonin reuptake inhibitors (SSRIs) are less expansion of the QT period and lower cardio toxic side effects. The aim of this study was to investigate QTc intervals and prognosis of the patients who come to the emergency service due to TCA and SSRI group antidepressant drug poisoning. In a study of 96 patients, 75 of whom were diagnosed to be poisoned by TCAs (TCA group) and 21 by SSRIs (SSRI group) were examined. Electrocardiographic alterations and QTc intervals all of patients were evaluated. QTc intervals of patients in TCA group were determined to be slightly more than those in SSRI group and it was not statistically significant. In the SSRI group, only one patient had QTc period more than 500 milliseconds (520 milliseconds); however, TCA overdose showed 9 (12%) patients with QTc interval over 500 milliseconds, and QTc values of 2 patients were over 600 milliseconds. In our study, it was determined that SSRI group drugs caused similar expansion of the QTc period as TCA drugs but they did not reach high values like TCA drugs, and their OTc intervals stayed in more innocent levels.

Risk assessment of severe tricyclic antidepressant overdose

Prognostic factors for severe complications in tricyclic antidepressant (TCA) overdose remain unclear. We therefore evaluated the value of clinical characteristics and electrocardiograph (ECG) parameters to predict serious events (seizures, arrhythmia, death) in severe TCA overdose of 100 patients using logistic regression models for risk assessment. The overall fatality rate was 6%, arrhythmia occurred in 21% and 31% of the patients developed seizures. Using an univariable logistic regression model, the maximal QRS interval (OR 1.22; 95% CI 1.06-1.41; p = .005), the time lag between ingestion and occurrence of first symptoms of overdose (OR 1.13; 95% CI 0.99-1.29; p = .072) and the age (OR 0.73; 95% CI 0.55-0.98; p = .038) were determined as the solely predictive parameters. In the multivariable logistic regression model, the QRS interval could not be established as independent predictor, however, the terminal 40-ms frontal plane QRS vector (T40) reached statistical significance regarding prediction of serious events (odds ration [OR] 1.70; 95% confidence interval [CI] 1.02-2.84; p = .041), along with age and time lag between ingestion and onset of symptoms of overdose with a sensitivity and specificity of 71% and 70%, respectively. Evaluation of both clinical characteristics and ECG-parameters in the early stage of TCA overdose may help to identify those patients who urgently need further aggressive medical observation and management.

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.

Acute poisoning: understanding 90% of cases in a nutshell

The acutely poisoned patient remains a common problem facing doctors working in acute medicine in the United Kingdom and worldwide. This review examines the initial management of the acutely poisoned patient. Aspects of general management are reviewed including immediate interventions, investigations, gastrointestinal decontamination techniques, use of antidotes, methods to increase poison elimination, and psychological assessment. More common and serious poisonings caused by paracetamol, salicylates, opioids, tricyclic antidepressants, selective serotonin reuptake inhibitors, benzodiazepines, non-steroidal anti-inflammatory drugs, and cocaine are discussed in detail. Specific aspects of common paediatric poisonings are reviewed.

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.

The limited utility of electrocardiography variables used to predict arrhythmia in psychotropic drug overdose

OBJECTIVE

The aim of the present study was to examine the relationship between serious arrhythmias in patients with psychotropic drug overdose and electrocardiography (ECG) findings that have been suggested previously to predict this complication.

METHODS

Thirty-nine patients with serious arrhythmias (ventricular tachycardia, supraventricular tachycardia or cardiac arrest) after tricyclic antidepressant overdose or thioridazine overdose were compared with 117 controls with clinically significant overdose matched to each case for the drug ingested. These patients with psychotropic drug overdose had presented for treatment to the Department of Clinical Toxicology, Newcastle and to the Princess Alexandra Hospital, Brisbane. The heart rate, the QRS width, the QTc and QT intervals, the QT dispersion, and the R wave and R/S ratios in aVR on the initial ECGs were compared in cases and controls.

RESULTS

The cases had taken dothiepin (16 patients), doxepin (six patients), thioridazine (five patients), amitriptyline (five patients), nortriptyline (three patients), imipramine (one patient) and a combination of dothiepin and thioridazine (three patients). In 20 of the 39 patients with arrhythmias, the arrhythmia had been a presumed ventricular tachycardia. Of the other 19 patients, 15 patients had a supraventricular tachycardia, two patients had cardiac arrests (one asystole, one without ECG monitoring) and two patients had insufficient data recorded to make classification of the arrhythmias possible. The QRS was >/= 100 ms in 82% of cases but also in 76% of controls. QRS >/= 160 ms had a sensitivity of only 13% and occurred in 2% of controls. QRS > 120 ms, QTc > 500 and the R/S ratio in aVR appeared to have a stronger association with the occurrence of arrhythmia: QRS > 120 ms (odds ratio [OR], 3.56; 95% confidence interval [CI], 1.46-8.68), QTc > 500 (OR, 3.07; 95% CI, 1.33-7.07), and R/S ratio in aVR > 0.7 (OR, 16; 95% CI, 3.47-74). Excluding thioridazine overdoses and performing the analysis for tricyclic antidepressant overdoses alone gave increased odds ratios for QRS > 120 ms (OR, 4.83; 95% CI, 1.73-13.5) and QTc > 500 (OR, 4.5; 95% CI, 1.56-13) but had little effect on that for the R/S ratio in aVR > 0.7 (OR, 14.5; 95% CI, 3.10-68).

CONCLUSION

ECG measurements were generally weakly related to the occurrence of arrhythmia and should not be used as the sole criteria for risk assessment in tricyclic antidepressant overdose. The frequently recommended practice of using either QRS >/= 100 ms or QRS >/= 160 ms to predict arrhythmias is not supported by our study. R/S ratio in aVR > 0.7 was most strongly related to arrhythmia but had estimated positive and negative predictive values of only 41% and 95%, respectively. The use of these specific predictors in other drug overdoses is not recommended without specific studies.

Antidepressants, old and new. A review of their adverse effects and toxicity in overdose

The newer antidepressants are as efficacious as the older agents in the treatment of depression. They have a side effect profile that is different from the older drugs and are generally better tolerated. Drug-drug interactions do exist with some of these agents and can usually be predicted from knowledge of their metabolism. When taken in overdose as the sole agents they are rarely fatal; seizures, nausea, vomiting, decreased level of consciousness, and tachycardia are common. In combination with other drugs, toxicity can be more severe. The serotonin syndrome can occur with many of these drugs, and the emergency physician must be vigilant in the evaluation of the overdose patient. CAs and older MAOIs are still in use and remain dangerous when taken in overdose. Patients asymptomatic after a period of observation in the ED usually can be discharged after psychiatric evaluation, when it is required.

Abnormal ventricular repolarization mimicking myocardial infarction after heterocyclic antidepressant overdose

In 2 young adult women who experienced acute heterocyclic antidepressant intoxication, we found a quite unusual electrocardiographic pattern characterized by abnormal ST-tract elevation in the right precordial leads associated with a marked QRS widening (right bundle branch block and left anterior fascicular block type). Because serum electrolyte imbalance and acute myocardial ischemic events were excluded, the mechanism by which antidepressant overdose may produce such elevation of the ST tract remains unclear.

Decreased R-R variation: a criterium for overdosage of tricyclic psychotropic drugs

OBJECTIVE

Since intoxication with tricyclic antidepressants is common, a supplementary screening method for differentiation between therapeutic and supratherapeutic ranges would be a valuable diagnostic tool, particularly in delirious and unconscious patients.

SETTING

108 patients treated with amitriptyline, 8 patients treated with doxepin, 10 patients treated with clozapine, and 72 normal control subjects matched for age and sex were tested for heart rate variability while resting.

RESULTS

Considering time and frequency derived measures, which are rather independent of heart rate, the patients showed significantly decreased heart rate variability parameters (p < 0.0001), as compared with the normal subjects. Of the patients presenting delirious symptoms 6 showed coefficients of variation more than 4 standard deviations below the mean control value.

CONCLUSIONS

As heart rate variability can be easily calculated, this measurement is suggested as a useful tool to quickly exclude or support the diagnosis of chronic intoxication with tricyclic antidepressants or clozapine.

Cardiovascular effects of carbamazepine toxicity

STUDY OBJECTIVE

To evaluate the cardiovascular effects of carbamazepine in patients presenting to the emergency department.

DESIGN

A retrospective case series from February 1, 1985, to July 30, 1993.

SETTING

Six urban EDs.

PARTICIPANTS

Seventy-two adult and pediatric patients with serum carbamazepine concentrations greater than 12 micrograms/mL and concurrent 12-lead ECGs.

RESULTS

The mean carbamazepine level was 24 micrograms/mL (range, 12.6 to 55 micrograms/mL). Minor ECG abnormalities were noted but no clinically significant arrhythmias were found. No correlation was found between carbamazepine concentration and heart rate or PR, QRS, or corrected QT intervals. Four adult patients had transient hypotension.

CONCLUSION

Clinically significant cardiovascular toxicity occurs rarely in patients with toxic carbamazepine concentrations. ECG findings do not correlate with serum carbamazepine concentration.

Cyclic antidepressant toxicity in children and adolescents

We retrospectively evaluated the clinical and laboratory findings of all patients admitted to our facility during a 6.5-year period with a history of cyclic antidepressant ingestion (CAD). Outcome parameters [admission CAD concentration, arterial pH, and corrected QT (QTc) and QRS intervals] used in adult populations to predict morbidity after CAD ingestion were applied to our study population. During the study period, 45 patients (mean +/- SD age of 11.8 +/- 5.6 years) were admitted with CAD ingestion. Conduction delays were present in 17 patients, 9 of whom had QTc intervals greater than 0.43 seconds. Seven patients had generalized seizures; 7 required mechanical ventilation; 14 had Glasgow Coma Scores of 8 or lower on presentation; and one required pharmacologic support for hypotension. In our cohort, the mean admission serum CAD concentration was 461.5 +/- 477.4 ng/mL. Correlations were found between the arterial pH, the QRS interval, the QTc interval, and the admission CAD serum concentration. In an analysis of three subsets of patients (i.e., those with seizures, coma, and respiratory insufficiency), only patients who presented with seizures were found to have a significant prolongation in the QRS and QTc intervals. Pediatric patients who have ingested CADs and present with seizures would appear to be at increased risk for having conduction delays, cardiac dysrhythmias, and, presumably, attendant morbidity and mortality associated with an ingestion.

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.