Value of the QRS duration versus the serum drug level in predicting seizures and ventricular arrhythmias after an acute overdose of tricyclic antidepressants

Utility of the electrocardiogram in drug overdose and poisoning: theoretical considerations and clinical implications

The ECG is a rapidly available clinical tool that can help clinicians manage poisoned patients. Specific myocardial effects of cardiotoxic drugs have well-described electrocardiographic manifestations. In the practice of clinical toxicology, classic ECG changes may hint at blockade of ion channels, alterations of adrenergic tone, or dysfunctional metabolic activity of the myocardium. This review will offer a structured approach to ECG interpretation in poisoned patients with a focus on clinical implications and ECG-based management recommendations in the initial evaluation of patients with acute cardiotoxicity.

Heart rate variability in children with tricyclic antidepressant intoxication

The aim of this study was to evaluate HRV in children requiring intensive care unit stays due to TCA poisoning between March 2009 and July 2010. In the time-domain nonspectral evaluation, the SDNN (P < 0.001), SDNNi (P < 0.05), RMSDD (P < 0.01), and pNN50 (P < 0.01) were found to be significantly lower in the TCA intoxication group. The spectral analysis of the data recorded during the first 5 minutes after intensive care unit admission showed that the values of the nLF (P < 0.05) and the LF/HF ratio (P = 0.001) were significantly higher in the TCA intoxication group, while the nHF (P = 0.001) values were significantly lower. The frequency-domain spectral analysis of the data recorded during the last 5 minutes showed a lower nHF (P = 0.001) in the TCA intoxication group than in the controls, and the LF/HF ratio was significantly higher (P < 0.05) in the intoxication group. The LF/HF ratio was higher in the seven children with seizures (P < 0.001). These findings provided us with a starting point for the value of HRV analysis in determining the risk of arrhythmia and convulsion in TCA poisoning patients. HRV can be used as a noninvasive testing method in determining the treatment and prognosis of TCA poisoning patients.

Hemodiafiltration: a novel approach for treating severe amitriptyline intoxication

Tricyclic antidepressant overdose is one of the most common cause of serious drug poisonings. Sometimes amitriptyline intoxication can be difficult to treat with standard treatments. At that case hemodiafiltration (HD) can be an eligible choice. We report a successful treatment of severe case using hemodiafiltration in addition to the supportive measures. Management with gastric lavage, activated charcoal, alkalinization and supportive care is the common approach and not enough for patients in deep coma. We satisfied that HD may have a beneficial role in lethal doses of amitriptyline as an additional therapy.

Rhabdomyolysis as a manifestation of clomipramine poisoning

CONTEXT

Tricyclic antidepressive agents are widely used in suicide attempts and present a variety of deleterious effects. Rhabdomyolysis is a rare complication of such poisoning.

CASE REPORT

A 55-year-old woman ingested 120 pills of 25 mg clomipramine in a suicide attempt two days before admission. After gastric lavage in another emergency department on the day of intake, 80 pills were removed. On admission to our department, she was disoriented, complaining of a dry mouth and tremors at the extremities. An electrocardiogram showed a sinus rhythm with narrow QRS complexes. Laboratory results showed high creatine phosphokinase (CK = 15,094 U/l on admission; normal range = 26 to 140 U/l), hypocalcemia, slightly increased serum transaminases and mild metabolic acidosis. The patient's medical history included depression with previous suicide attempts, obsessive-compulsive disorder, hypothyroidism and osteoporosis. She presented cardiac arrest with pulseless electric activity for seven minutes and afterwards, without sedation, showed continuous side-to-side eye movement. She developed refractory hypotension, with need for vasopressors. Ceftriaxone and clindamycin administration was started because of a hypothesis of bronchoaspiration. The patient remained unresponsive even without sedation, with continuous side-to-side eye movement and a decerebrate posture. She died two months later. Rhabdomyolysis is a very rare complication of poisoning due to tricyclic drugs. It had only previously been described after an overdose of cyclobenzaprine, which has a toxicity profile similar to tricyclic drugs.

CONCLUSIONS

Although arrhythmia is the most important complication, rhabdomyolysis should be investigated in cases of clomipramine poisoning.

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.

Detection and quantification of tricyclic antidepressants and other psychoactive drugs in urine by HPLC/MS/MS for pain management compliance testing

A sensitive, specific, and rapid high-pressure liquid chromatography/mass spectrometry/mass spectrometry method was developed for the quantitation of 11 tricyclic antidepressants and/or their metabolites; fluoxetine and norfluoxetine; cyclobenzaprine; and trazodone in urine. Samples were alkalinized with 0.2 N NaOH and extracted into 2 ml of hexane: ethyl acetate (1:1), evaporated to dryness, and reconstituted with 100 μl of 20 mM ammonium formate: methanol (20:80). The chromatographic separation was performed using an Allure Biphenyl 100 × 3.2 mm, 5-μ column with a mobile phase consisting of 20 mM ammonium formate: methanol (20:80 v/v) at a flow rate of 0.5 ml/min. The detection was accomplished by multiple-reaction monitoring via electrospray ionization source operating in the positive ionization mode. The calibration curve was linear over the investigated concentration range, 25-2,000 ng/ml, for each analyte using 1.0 ml of urine. The lower limit of quantitation for each analyte was 25 ng/ml. The intra- and inter-day precisions had coefficient of variation less than 15% and the accuracy was within the range from 88% to 109%. The method proved adequate for the tricyclic antidepressants analysis of urine for emergency clinical toxicology and pain management compliance testing.

Incidence of adverse cardiovascular events in adults following drug overdose

OBJECTIVES

Drug overdose is a leading cause of cardiac arrest and is currently the second leading cause of overall injury-related fatality in the United States. Despite these statistics, the incidence of adverse cardiovascular events (ACVEs) in emergency department (ED) patients following acute drug overdose is unknown. With this study, we address the 2010 American Heart Association Emergency Cardiovascular Care update calling for research to characterize the incidence of in-hospital ACVE following drug overdose.

METHODS

This was a prospective cohort study at two tertiary care hospitals over 12 months. Consecutive adult ED patients with acute drug overdose were prospectively followed to hospital discharge. The main outcome was occurrence of in-hospital ACVE, defined as the occurrence of one or more of the following: myocardial injury, shock, ventricular dysrhythmia, and cardiac arrest.

RESULTS

There were 459 ED patients with suspected drug overdose, of whom 274 acute drug overdose qualified and were included for analysis (mean [± SE] age=40.3 [± 1.0] years; 63% male). Hospital course was complicated by ACVE in 16 patients (some had more than one): 12 myocardial injury, three shock, two dysrhythmia, and three cardiac arrest. The incidence of ACVE was 5.8% overall (95% confidence interval [CI]=3.6% to 9.3%) and 10.7% (95% CI=6.6% to 16.9%) among inpatient admissions, with all-cause mortality at 0.7% (95% CI=0.2% to 2.6%).

CONCLUSIONS

Based on this study of adult patients with acute drug overdose, ACVE may occur in up to 9.3% overall and up to 16.9% of hospital admissions. Implications for the evaluation and triage of ED patients with acute drug overdose require further study with regard to optimizing interventions to prevent adverse events.

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.

Timing and frequency of physostigmine redosing for antimuscarinic toxicity

We sought to determine how frequently antimuscarinic-poisoned patients receiving physostigmine receive multiple doses of physostigmine, the length of time between physostigmine doses, and what impact multiple doses of physostigmine have on the disposition and total length of hospital stay. We performed a retrospective chart review of patients given physostigmine for likely antimuscarinic toxicity. A total of 45 patients met inclusion criteria. We abstracted patient demographics, vital signs, physical exam findings, electrocardiograms, the timing and dose of physostigmine, the implicated antimuscarinic agents, and disposition from the hospital. We counted the number of patients who required multiple physostigmine doses and calculated the time to repeat dosing. Fourteen of the 45 patients (31%) given physostigmine for antimuscarinic toxicity received multiple doses: nine patients (20%) received two doses, three patients (6.6%) received three doses, and two patients (4.4%) received four doses. Less than 5.5 h elapsed between sequential physostigmine doses, and less than 6.5 h elapsed between the first and last dose. Forty-five percent of patients receiving one dose of physostigmine were discharged from the emergency department (ED) and 36% of patients receiving more than one dose of physostigmine were discharged from the ED. Whether admitted or discharged, there was no statistically significant difference in the length of hospital stay between patients receiving one or multiple doses of physostigmine. Repeated physostigmine administration is not frequently needed in medication-induced antimuscarinic toxicity. Patients are not likely to require further physostigmine redosing more than 6.5 h from their first dose.

Temporary cardiac pacemaker in the treatment of junctional rhythm and hypotension due to imipramine intoxication

Tricyclic antidepressants (TCAs) account for approximately 3% of all pediatric hospitalizations due to poisoning. TCAs remain a common cause of fatal drug poisoning because of their cardiovascular toxicity as manifested by electrocardiogram (ECG) abnormalities, arrhythmias, and hypotension. We report a 15-year-old girl with junctional escape rhythm and resistant hypotension caused by severe imipramine intoxication. Initial ECG showed junctional escape rhythm (46 bpm) with no atrial activity, low QRS voltage, widening of the QRS complex (160 ms) with a right bundle branch-like pattern, R wave > 3 mm in aVR (6 mm), and prolongation of the QT interval (QTc 550 ms). Despite intravenous fluids and inotropic support, she had resistant hypotension and acute renal failure. Junctional rhythm was successfully terminated by using temporary cardiac pacemaker. Hemodialysis and hemoperfusion were also performed. She was discharged on the day 5 without any complications. During follow-up, no ECG abnormalities were noted. We reported successful use of temporary cardiac pacemaker for treatment of junctional rhythm and resistant hypotension in imipramine intoxication. The conventional methods of activated charcoal, alkalinization, and symptomatic treatment of complications are usually enough for nonlethal doses of TCA intoxication. However, in imipramine intoxication with serious arrythmias and hypotension, using temporary cardiac pacemaker, hemodialysis, and hemoperfusion can be a life-saving therapeutic approach.

Toxicology today: what you need to know now

Clinicians are frequently confronted with toxicological emergencies and challenged with the task of correctly identifying the possible agents involved and providing appropriate treatments. In this review article, we describe the epidemiology of overdoses, provide a practical approach to the recognition and diagnosis of classic toxidromes, and discuss the initial management strategies that should be considered in all overdoses. In addition, we evaluate some of the most common agents involved in poisonings and present their respective treatments. Recognition of toxidromes with knowledge of indications for antidotes and their limitations for treating overdoses is crucial for the acute care of poisoned patients.

Toxin-related seizures

Toxin-related seizures result from an imbalance in the brain's equilibrium of excitation-inhibition. Fortunately, most toxin-related seizures respond to standard therapy using benzodiazepines. However, a few alterations in the standard approach are recommended to ensure optimal care and expedient termination of seizure activity. If 2 doses of a benzodiazepine do not terminate the seizure activity, a therapeutic dose of pyridoxine (5 g intravenously in an adult and 70 mg/kg intravenously in a child) should be considered. Phenytoin should be avoided because it is ineffective for many toxin-induced seizures and is potentially harmful when used to treat seizures induced by theophylline or cyclic antidepressants.

Electrocardiographic predictors of adverse cardiovascular events in suspected poisoning

Poisoning is the second leading cause of injury-related fatality in the USA and the leading cause of cardiac arrest in victims under 40 years of age. The study objective was to define the electrocardiographic (ECG) predictors of adverse cardiovascular events (ACVE) complicating suspected acute poisoning (SAP). This was a case-control study in adults at three tertiary-care hospitals and one regional Poison Control Center. We compared 34 cases of SAP complicated by ACVE to 101 consecutive control patients with uncomplicated SAP. The initial ECG was analyzed for rhythm, intervals, QT dispersion, ischemia, and infarction. ECGs were interpreted by a cardiologist, blinded to study hypothesis and case data. Subjects were 48% male, with mean age 42 +/- 19 years. In addition to clinical suspicion of poisoning in 100% of patients, routine toxicology screens were positive in 77%, most commonly for benzodiazepines, opioids, and/or acetaminophen. Neither the ventricular rate, the QRS duration, nor the presence of infarction predicted the risk of ACVE. However, the rhythm, QTc, QT dispersion, and presence of ischemia correlated with the risk of ACVE. Independent predictors of ACVE based on multivariable logistic regression were prolonged QTc, any non-sinus rhythm, ventricular ectopy, and ischemia. Recursive partitioning analysis identified very low risk criteria (94.1% sensitivity, 96.2% NPV) and high risk criteria (95% specificity). Among patients with SAP, the presence of QTc prolongation, QT dispersion, ventricular ectopy, any non-sinus rhythm, and evidence of ischemia on the initial ECG are strongly associated with ACVE.

Incidence of tricyclic antidepressant-like complications after cyclobenzaprine overdose

BACKGROUND

The cyclobenzaprine structure is similar to amitriptyline; however, tricyclic antidepressant (TCA)-like wide complex dysrhythmia has not been reported. Our objective was to determine the incidence of TCA-like effects in cyclobenzaprine overdoses as reported to 6 poison centers for 2 years. We compared the incidence of these effects to amitriptyline overdoses collected during the same period.

METHODS

We performed a retrospective review of 2 years of cases as reported to the Texas Poison Center Network. We identified sole ingestions of cyclobenzaprine and of amitriptyline. Cases had a recorded clinical outcome and clinical effect. A trained reviewer used a standard data collection sheet within a secured electronic database. One investigator audited a random sample of charts.

RESULTS

We identified 3974 cases of cyclobenzaprine calls. Of these, we collected 209 cases of acute overdoses without coingestions. There were no deaths. No cases of cyclobenzaprine ingestions were reported to have died or have a wide QRS or ventricular dysrhythmia. Seizures were reported in 2 cases; however, both were unrelated to cyclobenzaprine. Hypotension was reported in 1.4% (3/209) of cases, and a vasopressor was used in one case (0.5%). Patients with an amitriptyline overdose were more likely to have seizure, coma, tachycardia, a wide QRS or ventricular dysrhythmia, and have received sodium bicarbonate or be intubated.

CONCLUSIONS

Cyclobenzaprine overdoses were not reported to cause widened QRS, ventricular dysrhythmias, or seizures, and hypotension was rarely reported. Tricyclic antidepressant-related effects occurred more often in our comparison group of amitriptyline overdoses.

Proarrhythmic risk with antipsychotic and antidepressant drugs: implications in the elderly

The quinidine-like effects of some antidepressant drugs (particularly tricyclic antidepressants) and many antipsychotic drugs (particularly the phenothiazines) confound treatment of psychosis and depression in patients with major mental illness. This is especially true among elderly patients with existing risk factors for corrected QT (QTc) interval prolongation. We used PubMed, previously reported review articles and the extensive personal files of the authors to identify cases of subjects aged>or=60 years who developed QTc interval prolongation, polymorphic ventricular tachycardia (PVT)/torsade de pointes (TdP) and/or sudden cardiac death while taking antipsychotic or antidepressant drugs or a combination of these medications. We identified 37 patients who had taken, in total, 46 antipsychotic or antidepressant drugs. Our most striking finding was that almost four-fifths of our cases involved women. When the 14 critically ill subjects receiving haloperidol intravenously were excluded, 91.3% of our subjects were women. Almost three-quarters of our study subjects had cardiovascular disease. Intravenous administration of haloperidol in the critically ill and profoundly agitated elderly warrants particular comment. Of the 14 subjects in this category identified, six were men and eight were women. In 13 cases, the drug dose far exceeded the 2 mg necessary to produce an antipsychotic effect. These clinicians were using an agent to achieve sedation that usually requires very high doses in the critically ill and profoundly agitated elderly to achieve this effect. Inclusion criteria for our literature review required antipsychotic and/or antidepressant drug-induced QTc interval prolongation. Even so, our finding that 31 of our 37 subjects developed PVT is sobering. However, the reader should not conclude that drug-induced QTc interval prolongation is highly predictive of PVT or its TdP subtype. All of our study subjects had at least two risk factors for TdP, with age and sex being the most common. We included the rare case of a patient with congenital long QT syndrome who developed further lengthening of the QTc interval and TdP when prescribed an antidepressant drug well known to produce QTc interval prolongation. We conclude with recommendations for clinicians not expert in the specialty of cardiology to deal with the many questions raised in this review. Specifically, such clinicians treating elderly patients with antipsychotic and antidepressant drugs that may prolong the QTc interval should aggressively obtain a baseline ECG for elderly female patients with additional risk factors such as personal or family history of pre-syncope or syncope, electrolyte disturbances or cardiovascular disease. Elderly male patients are also subject to QTc interval prolongation when such risk factors are present. It is important that the clinicians themselves inspect ECGs. If the QT interval is more than half the RR interval, QTc interval prolongation is likely to be present. In such cases, a cardiology colleague interested in QTc interval issues and TdP should be asked to review the ECG. Finally, nothing in our recommendations replaces meticulous attention to US FDA guidelines in the package insert of each drug.

Evaluating the Role of a Triage Electrocardiogram Protocol at an Urban Emergency Department

Objective

Our emergency department (ED) performs triage ECG for a variety of complaints to identify patients in need of treatment escalation. The aim of this study was to evaluate the existing triage ECG protocol as a means of treatment decision making.

Methods

This prospective observational study was conducted in an urban ED over one week. We recruited all patients aged 18 years and above with an undiagnosed complaint requiring a triage ECG based on the existing departmental protocol. As part of the protocol, an experienced emergency doctor then reviewed the ECG to determine the need for treatment escalation. Explicit data collection was performed using our electronic database. The outcome measures were proportions of triage treatment escalations, reasons for escalation and disposition status. Analysis was by descriptive statistics.

Results

739 patients were recruited from a total attendance of 3228. The rate of triage ECG was 23%. There were 22 (3%) triage escalations. Usually each escalation resulted from a combination of reasons. These included important ECG changes (77%), abnormal vital signs (5%) and ongoing symptoms (95%).

Conclusions

The triage ECG protocol resulted in important escalations in a small proportion of presentations. Future research is needed to refine guidelines on the use of triage ECG for different ED complaints.

Drugs and pharmaceuticals: management of intoxication and antidotes

The treatment of patients poisoned with drugs and pharmaceuticals can be quite challenging. Diverse exposure circumstances, varied clinical presentations, unique patient-specific factors, and inconsistent diagnostic and therapeutic infrastructure support, coupled with relatively few definitive antidotes, may complicate evaluation and management. The historical approach to poisoned patients (patient arousal, toxin elimination, and toxin identification) has given way to rigorous attention to the fundamental aspects of basic life support--airway management, oxygenation and ventilation, circulatory competence, thermoregulation, and substrate availability. Selected patients may benefit from methods to alter toxin pharmacokinetics to minimize systemic, target organ, or tissue compartment exposure (either by decreasing absorption or increasing elimination). These may include syrup of ipecac, orogastric lavage, activated single- or multi-dose charcoal, whole bowel irrigation, endoscopy and surgery, urinary alkalinization, saline diuresis, or extracorporeal methods (hemodialysis, charcoal hemoperfusion, continuous venovenous hemofiltration, and exchange transfusion). Pharmaceutical adjuncts and antidotes may be useful in toxicant-induced hyperthermias. In the context of analgesic, anti-inflammatory, anticholinergic, anticonvulsant, antihyperglycemic, antimicrobial, antineoplastic, cardiovascular, opioid, or sedative-hypnotic agents overdose, N-acetylcysteine, physostigmine, L-carnitine, dextrose, octreotide, pyridoxine, dexrazoxane, leucovorin, glucarpidase, atropine, calcium, digoxin-specific antibody fragments, glucagon, high-dose insulin euglycemia therapy, lipid emulsion, magnesium, sodium bicarbonate, naloxone, and flumazenil are specifically reviewed. In summary, patients generally benefit from aggressive support of vital functions, careful history and physical examination, specific laboratory analyses, a thoughtful consideration of the risks and benefits of decontamination and enhanced elimination, and the use of specific antidotes where warranted. Data supporting antidotes effectiveness vary considerably. Clinicians are encouraged to utilize consultation with regional poison centers or those with toxicology training to assist with diagnosis, management, and administration of antidotes, particularly in unfamiliar cases.

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.

Clinical, electrocardiographic, and laboratory findings in children with amitriptyline intoxication

BACKGROUND

Amitriptyline is one of the major tricyclic antidepressants, and the data on amitriptyline poisoning in children are limited.

OBJECTIVES

To present our experiences with amitriptyline poisoning in children, particularly with regard to its effects on electrocardiogram (ECG) and relation with clinical status.

METHODS

Clinical, laboratory, and electrocardiographic findings in 52 children admitted with amitriptyline poisoning were reviewed. Patients were divided into 2 groups according to age, as 6 years or younger (group A) and older than 6 years (group B).

RESULTS

Mean age was 4.6 +/- 3.0 years. Thirty-one patients were male, and 41 were 6 years or younger. Ingested amitriptyline dose was known in 23 patients (range, 2.3 mg/kg-27 mg/kg). The most frequent findings were lethargy (76.9%), sinus tachycardia (57.7%), and coma (48.1%). Four patients had a history of convulsion. The most common laboratory abnormalities were hyponatremia (26.9%) and leukocytosis (25%). Elevated transaminase levels were observed in 4 patients. In ECG, 11 (22.4%) patients had QTc prolongation and in 4 (8.2%) of them, it was significant. In 4 patients (8.2%), the QRS duration was 100 ms or longer and in 15 patients, the R wave in aVR was 3 mm or longer. The frequencies of clinical, laboratory, and electrocardiographic findings were similar between the 2 age groups (P > 0.05). No clinically apparent arrhythmias were observed. The positive predictive value of a widened QRS was 100% in terms of coma. None of the patients with an R wave in aVR of less than 3 mm developed convulsion; thus, the negative predictive value of an R wave in aVR of 3 mm or longer was 100% in terms of convulsion.

CONCLUSIONS

Amitriptyline poisoning may result in severe toxicity. Frequencies of clinical, laboratory, and ECG findings were similar in the 2 age groups. Amitriptyline overdose results in some ECG changes that can possibly help to predict the results of poisoning. Absence of an R wave in aVR of 3 mm or longer predicts seizures with a high negative predictive value, and a QRS duration of 100 or longer ms predicts coma with a high positive predictive value.

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).

Clinical review: aggressive management and extracorporeal support for drug-induced cardiotoxicity

Poisoning may induce failure in multiple organs, leading to death. Supportive treatments and supplementation of failing organs are usually efficient. In contrast, the usefulness of cardiopulmonary bypass in drug-induced shock remains a matter of debate. The majority of deaths results from poisoning with membrane stabilising agents and calcium channel blockers. There is a need for more aggressive treatment in patients not responding to conventional treatments. The development of new antidotes is limited. In contrast, experimental studies support the hypothesis that cardiopulmonary bypass is life-saving. A review of the literature shows that cardiopulmonary bypass of the poisoned heart is feasible. The largest experience has resulted from the use of peripheral cardiopulmonary bypass. However, a literature review does not allow any conclusions regarding the efficiency and indications for this invasive method. Indeed, the majority of reports are single cases, with only one series of seven patients. Appealing results suggest that further studies are needed. Determination of prognostic factors predictive of refractoriness to conventional treatment for cardiotoxic poisonings is mandatory. These prognostic factors are specific for a toxicant or a class of toxicants. Knowledge of them will result in clarification of the indications for cardiopulmonary bypass in poisonings.

Should a benzodiazepine antagonist be used in unconscious patients presenting to the emergency department?

Patients in coma with suspected drug poisoning are commonly encountered in the emergency department. Benzodiazepines are one of the most commonly used drugs in self-poisoning. Flumazenil, a benzodiazepine antagonist has been suggested as a diagnostic and treatment tool in suspected poisoning of unclear cause, but caution is required due to potential side effects. No systemic review of this literature has been done on this topic.

OBJECTIVES

The aim of this study is to examine if flumazenil should be used in patients with coma from suspected drug poisoning.

SEARCH STRATEGY

Randomised controlled trials were identified from the Cochrane Library, Pubmed and EMBASE. Bibliographies from included studies, known reviews and texts were searched. Content experts were contacted.

SELECTION CRITERIA

Randomised controlled trials were eligible for inclusion. Studies were included if patients who presented with altered mental state from suspected drug poisoning were treated with intravenous flumazenil as compared to placebo.

DATA COLLECTION AND ANALYSIS

Data were extracted and methodological quality was assessed independently by two reviewers.

MAIN RESULTS

Seven randomised controlled trials were included. A total of 466 patients were involved. Flumazenil was found to reverse coma from suspected drug poisoning with a relative benefit of 4.45 (95% CI 2.65, 7.45). In terms of major side effects, there was no statistical difference between flumazenil and placebo (RR 2.86, 95% CI 0.12-69.32). However, in terms of minor side effects, flumazenil was associated with a higher incidence of anxiety (RR 2.84, 95% CI 1.28-6.30) and other side effects (RR 3.73, 95% CI 2.078-6.73). There was no difference in the incidence of vomiting (RR 4.28, 95% CI 0.95-19.35).

CONCLUSION

Current evidence shows that flumazenil may be effective in the reversal of coma in patients presenting to the emergency department with coma from suspected drug poisoning.

Acute olanzapine-induced akathisia and dystonia in a patient discontinued from fluoxetine

The patient with acute extrapyramidal signs and symptoms presents a significant clinical challenge. We present the case of a young man who developed an acute akathisia and dystonia after inadvertent overdose of olanzapine (Zyprexa) in the setting of a recent discontinuation of fluoxetine. The receptor chemistry and mechanisms pertinent to his presentation are reviewed. An analysis of the literature indicates that a broad incidence range is cited for the extrapyramidal effects of these medications. We suggest a diagnostic and therapeutic approach to the undifferentiated patient presenting with extrapyramidal signs and symptoms. The possibility of neuroleptic malignant syndrome (NMS), serotonin syndrome (SS), tricyclic overdose, and cocaine abuse should be considered in a patient with extrapyramidal signs and symptoms, given the potential for complications. An emphasis is placed on the need for carefully verbalized discharge instructions to avoid a potential untoward outcome.

Extracorporeal life support in a case of acute carbamazepine poisoning with life-threatening refractory myocardial failure

OBJECTIVE

To report the efficacy of extracorporeal life support (ECLS) in acute carbamazepine poisoning with sustained refractory myocardial failure and a high degree of conductance disturbances.

DESIGN AND SETTING

Case report from the toxicological and medical intensive care unit in a university hospital.

PATIENT

A 26-year-old man with severe myocardial failure unresponsive to 1.7 microg kg(-1) min(-1) epinephrine and 1.9 microg kg(-1) min(-1) norepinephrine (SvO2, 17.8% and cardiac index, 0.8 l min(-1) m(-2)) following a suicidal ingestion of 32 g slow-release carbamazepine.

INTERVENTIONS

ECLS (Jostra-Maquet centrifugal pump (Rotaflow) connected to a hollow-fiber membrane oxygenator).

MEASUREMENTS AND RESULTS

ECLS device allowed inotropic drug weaning while maintaining end-organ function and supported the patient until myocardial recovery. The plasma carbamazepine level was 224 micromol/l on admission and peaked at 338 micromol/l 101 h after admission with a prolonged gastrointestinal absorption phase despite multiple doses of activated charcoal. The patient survived and was successfully explanted on day 6. An extensive and regressive thrombosis of the inferior vena cava was noted. Cardiac function totally recovered and at 2-year follow-up. There were no significant sequelae.

CONCLUSIONS

We report a case of life-threatening myocardial failure with conductance disturbances secondary to an acute carbamazepine poisoning, demonstrating the efficacy of ECLS to assist recovery.

A risk assessment based approach to the management of acute poisoning

Early assessment and management of poisoning constitutes a core emergency medicine competency. Medical and psychiatric emergencies coexist; the acute poisoning is a dynamic medical illness that represents an acute exacerbation of a chronic underlying psychosocial disorder. The emergency physician must use an approach that ensures early decisions address potentially time critical interventions, while allowing management to be tailored to the individual patient's needs in that particular medical setting. This article outlines a rationale approach to the management of the poisoned patient that emphasises the importance of early risk assessment. Ideally, this approach should be used in the setting of a health system designed to optimise the medical and psychosocial care of the poisoned patient.

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.

Prolonged clinical effects in modified-release amitriptyline poisoning

BACKGROUND

Tricyclic antidepressant poisoning is often associated with significant cardiovascular and central nervous system toxicity. Effective treatment includes the use of appropriate gastric decontamination techniques, the administration of sodium bicarbonate, and meticulous supportive care. Tricylcic antidepressant toxicity typically lasts 24-48 hours following a significant overdose.

CASE REPORT

We describe a case of tricyclic antidepressant poisoning where significant clinical toxicity (QRS prolongation, metabolic acidosis) was observed for up to 4 days following ingestion of a modified-release preparation of amitriptyline. Successful patient recovery was associated with the use of multidose activated charcoal and repeated administration of intravenous sodium bicarbonate.

CONCLUSIONS

Clinicians should be aware of the potential for prolonged tricyclic toxicity in patients who have ingested modified-release amitriptyline in overdose. Gastric decontamination techniques such as multidose activated charcoal and whole bowel irrigation should be considered where there is evidence of ongoing tricyclic antidepressant absorption or clinical toxicity following ingestion of a modified-release preparation. These interventions may be indicated for prolonged periods (greater than 36 hours) post ingestion.

A Critical Reconsideration of the Clinical Effects and Treatment Recommendations for Sodium Channel Blocking Drug Cardiotoxicity

The cardiac sodium channel is comprised of proteins that span the cardiac cell membrane and form the channel pore. Depolarisation causes the proteins to move and open the sodium channel. Once the channel is open (active conformation), sodium ions move into the cell. The channel then changes from the active conformation to an inactive conformation - the channel remains open, but influx of sodium ions ceases. Recovery occurs as the channel moves from the inactive conformation back to the closed conformation and is then ready to open following the next depolarisation. Sodium channel blocking drugs (NCBDs) occupy receptors in the channel during the active and inactive conformations. The drug dissociates from most of the channel receptors during recovery, but the time it takes the drug to dissociate slows recovery. The slowed recovery prolongs conduction time, the main toxicity of NCBD overdose. Conduction time is further prolonged if heart rate increases as there are more available active and inactive conformations/unit time, which increases channel receptor binding sites for the NCBD. In addition to prolonging conduction time, NCBDs also decrease inotropy. Treatment of NCBD cardiotoxicity has been based on in vitro and animal experiments, and case reports. Assumptions based on this evidence must now be reassessed. For example, canines consistently develop ventricular tachycardia (VT) when tricyclic antidepressants (TCAs) are administered. Much of the literature discussing NCBD cardiotoxicity assumes that TCA poisoning induces VT in humans with the same regularity that occurs in canines. Seemingly, in support of this assumption was the finding that patients with remote myocardial infarction developed VT when therapeutically ingesting a NCBD. However, conduction is prolonged in myocardium that is or has been ischaemic. NCBD prolong conduction more in previously ischaemic myocardium than in normal myocardium, which causes nonuniform conduction and allows the development of re-entrant arrhythmias such as VT. Although some nonuniform conduction may occur in the healthy heart following a NCBD overdose, there is no evidence that nonuniform conduction occurs to the extent that it will cause re-entrant arrhythmias in this setting. Using various animal models and a variety of NCBDs, sodium ions, bicarbonate ions and alkalosis have been compared for the treatment of ventricular arrhythmias, hypotension and mortality. The results of these experiments have been extrapolated to NCBD overdose in humans. Animal models and single treatment approaches may have narrowed our scope. More recent evidence indicates that properties of each individual NCBD may require unique treatment. There is limited evidence that glucagon, which increases initial sodium ion influx into the cardiac cell, should be considered early in the treatment of cardiotoxicity. Another consideration may be treatment of NCBD with faster kinetics. Conduction time is decreased if a NCBD occupying the receptor is replaced by a NCBD that moves off and on the receptor more quickly. There is less evidence for this treatment, as risk may be greater. With greater understanding of the sodium channel and NCBDs, we must reassess our approach to the treatment of patients with healthy hearts who overdose on NCBD.

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.