Imipramine poisoning: survival of a child after prolonged cardiac massage

Survival after severe amitriptyline poisoning with prolonged ventricular tachycardia and cardiac arrest

Background

Tricyclic antidepressants (TCA) are becoming one of the most frequently used substances in self poisoning. Significant morbidity and mortality associated with TCA overdose are often related to and refractory hypotension. We report the first case of survival after severe amitriptyline poisoning, leading to prolonged cardiac arrest and ventricular tachycardia (VT), resuscitated with 3 h of uninterrupted cardiac massage and Direct current (DC) shocks.

Case presentation

A 25 year old girl presented with severe amitriptyline poisoning causing pulseless VT and prolonged cardiac arrest. After 3 h of uninterrupted external cardiac massage, together with nine DC shocks and intra venous bicarbonate injections the rhythm reverted to a nodal tachycardia, initial 2D echocardiogram showed left ventricular dysfunction, which recovered to normal after 2 weeks and the patient had a complete recovery subsequently.

Conclusion

Our case highlights the importance of continued resuscitation in patients presenting with TCA poisoning and resistant arrhythmia, especially in young and otherwise healthy patients.

Extracorporeal treatment for tricyclic antidepressant poisoning: recommendations from the EXTRIP Workgroup

The Extracorporeal Treatments In Poisoning (EXTRIP) workgroup was formed to provide recommendations on the use of extracorporeal treatments (ECTR) in poisoning. Here, the workgroup presents its results for tricyclic antidepressants (TCAs). After an extensive literature search, using a predefined methodology, the subgroup responsible for this poison reviewed the articles, extracted the data, summarized findings, and proposed structured voting statements following a predetermined format. A two-round modified Delphi method was chosen to reach a consensus on voting statements and RAND/UCLA Appropriateness Method to quantify disagreement. Blinded votes were compiled, returned, and discussed in person at a meeting. A second vote determined the final recommendations. Seventy-seven articles met inclusion criteria. Only case reports, case series, and one poor-quality observational study were identified yielding a very low quality of evidence for all recommendations. Data on 108 patients, including 12 fatalities, were abstracted. The workgroup concluded that TCAs are not dialyzable and made the following recommendation: ECTR is not recommended in severe TCA poisoning (1D). The workgroup considers that poisoned patients with TCAs are not likely to have a clinical benefit from extracorporeal removal and recommends it NOT to be used in TCA 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).

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.

Management of the Cardiovascular Complications of Tricyclic Antidepressant Poisoning

Experimental studies suggest that both alkalinisation and sodium loading are effective in reducing cardiotoxicity independently. Species and experimental differences may explain why sodium bicarbonate appears to work by sodium loading in some studies and by a pH change in others. In the only case series, the administration of intravenous sodium bicarbonate to achieve a systemic pH of 7.5-7.55 reduced QRS prolongation, reversed hypotension (although colloid was also given) and improved mental status in patients with moderate to severe tricyclic antidepressant poisoning. This clinical study supports the use of sodium bicarbonate in the management of the cardiovascular complications of tricyclic antidepressant poisoning. However, the clinical indications and dosing recommendations remain to be clarified. Hypotension should be managed initially by administration of colloid or crystalloid solutions, guided by central venous pressure monitoring. Based on experimental and clinical studies, sodium bicarbonate should then be administered. If hypotension persists despite adequate filling pressure and sodium bicarbonate administration, inotropic support should be initiated. In a non-randomised controlled trial in rats, epinephrine resulted in a higher survival rate and was superior to norepinephrine both when the drugs were used alone or when epinephrine was used in combination with sodium bicarbonate. Sodium bicarbonate alone resulted in a modest increase in survival rate but this increased markedly when sodium bicarbonate was used with epinephrine or norepinephrine. Clinical studies suggest benefit from norepinephrine and dopamine; in an uncontrolled study the former appeared more effective. Glucagon has also been of benefit. Experimental studies suggest extracorporeal circulation membrane oxygenation is also of potential value. The immediate treatment of arrhythmias involves correcting hypoxia, electrolyte abnormalities, hypotension and acidosis. Administration of sodium bicarbonate may resolve arrhythmias even in the absence of acidosis and, only if this therapy fails, should conventional antiarrhythmic drugs be used. The class 1b agent phenytoin may reverse conduction defects and may be used for resistant ventricular tachycardia. There is also limited evidence for benefit from magnesium infusion. However, class 1a and 1c antiarrhythmic drugs should be avoided since they worsen sodium channel blockade, further slow conduction velocity and depress contractility. Class II agents (beta-blockers) may also precipitate hypotension and cardiac arrest.

A prospective investigation into the epidemiology of in-hospital pediatric cardiopulmonary resuscitation using the international Utstein reporting style

OBJECTIVE

Data regarding pediatric in-hospital cardiopulmonary resuscitation (CPR) have been limited because of retrospective study designs, small sample sizes, and inconsistent definitions of cardiac arrest and CPR. The purpose of this study was to prospectively describe and evaluate pediatric in-hospital CPR with the international consensus-derived epidemiologic definitions from the Utstein guidelines.

METHODS

All 129 in-hospital CPRs during 12 months at a 122-bed university children's hospital in Sao Paulo, Brazil, were described and evaluated using Utstein reporting guidelines. These guidelines include standardized descriptions of hospital variables, patient variables, arrest/event variables, and outcome variables. CPR was defined as chest compressions and assisted ventilation provided because of cardiac arrest or because of severe bradycardia with poor perfusion. Outcome variables included sustained return of spontaneous circulation, 24-hour survival, 30-day survival, 1-year survival, and neurologic status of survivors by the Pediatric Cerebral Performance Category Scale.

RESULTS

Of the 6024 children admitted to the hospital, 176 (3%) had an episode that met the criteria for provision of CPR and 129 (2%) received CPR, 86 for clinical cardiac arrest and 43 for bradycardia with poor perfusion. Most of the children (71%) had preexisting chronic diseases. The most common precipitating causes were respiratory failure (61%) and shock (29%). The initial cardiac rhythm was asystole in 71 children (55%), pulseless electrical activity in 12 (9%), ventricular fibrillation in 1, and bradycardia with pulses and poor perfusion in 43 (33%). Eighty-three children (64%) attained sustained return of spontaneous circulation (>20 minutes), 43 (33%) were alive at 24 hours, 24 (19%) were alive at 30 days, and 19 (15%) were alive at 1 year. Although many factors correlated with 24-hour survival, multivariate logistic regression analysis revealed independent association of 24-hour survival with respiratory failure as the precipitating cause (odds ratio [OR]: 4.92; 95% confidence interval [CI]: 1.73-14.0), bradycardia with pulses as the initial event (OR: 2.68; 95% CI: 1.01-7.1), and shorter duration of CPR (OR: 0.92; 95% CI: 0.89-0.96 for each elapsed minute). Similarly, 30-day survival was independently associated with respiratory failure as the precipitating cause and shorter duration of CPR. Thirty-day survival decreased by 5% with each elapsed minute of CPR. Nineteen (91%) of the 21 survivors to hospital discharge and 16 (83%) of the 19 1-year survivors had no demonstrable long-term change in neurologic function from their pre-CPR status.

CONCLUSIONS

During this study, CPR was uncommon but not rare. Respiratory failure was the most common precipitating cause, followed by shock. Preexisting chronic diseases were prevalent among these children. Asystole was the most common initial cardiac rhythm, and bradycardia with pulses and poor perfusion was the second most common. Ventricular fibrillation was rare, but children with acute cardiac diseases, such as cardiac surgery and acute cardiomyopathies, were not admitted to this children's hospital. CPR was effective: nearly two thirds of these children were initially successfully resuscitated, and one third were alive at 24 hours compared with imminent death without CPR and advanced life support. Nevertheless, survival progressively decreased over time, generally as a result of the underlying disease process. One-year survival was 15%. Importantly, most of these survivors had no demonstrable change in gross neurologic function from their pre-CPR status.

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.

Part 8: advanced challenges in resuscitation. Section 2: toxicology in ECC. European Resuscitation Council

Use of standard ACLS protocols for all patients who are critically poisoned may not result in an optimal outcome. Care of severely poisoned patients can be enhanced by urgent consultation with a medical toxicologist. Alternative approaches required in severely poisoned patients include: o Higher doses than usual. o Drugs that are rarely used to treat cardiac arrest (amrinone, calcium, esmolol, glucagon, insulin, labetalol, phenylephrine, physostigmine, and sodium bicarbonate). o Heroic measures, such as prolonged CPR and use of circulatory assist devices. When resuscitation is unsuccessful, organ donation may still be an option.

A rationale for staged teaching of basic life support

Basic life support is a crucial part of the Chain of Survival. Unfortunately, however the skill is complex and cannot readily be acquired--let alone retained--in the course of a single training session. Although the problem has long been recognised, no new strategies have been widely implemented to counter the problem. We believe that staged teaching of CPR might provide a solution, and we have devised a program to test this new method. It involves three stages of instruction that we have called bronze, silver, and gold standards. The bronze standard involves opening the airway and providing chest compression without active ventilation: this alone may widen the window of opportunity for successful defibrillation in adult victims in out-of-hospital cardiac arrest. Ventilation is introduced at silver stage using a ratio of 50:5, with emphasis on its value in the resuscitation of children being used as motivation to bring people back for a second period of instruction. The gold stage teaches conventional CPR. A pilot study has been encouraging and a randomized trial on skill acquisition and skill retention is planned.

Pearls, pitfalls, and updates in toxicology

Pearls and pitfalls learned from our practical experiences caring for poisoned patients are presented. Clinical pearls include the following: using diagnostic tests to detect end-organ toxicity, applying physiologic principles to the management of hemodynamically unstable poisoned patients, and dealing with psychologic injuries from hazardous materials incidents. Recognizing serious complications from poisoning and adverse drug effects, including the serotonin syndrome, are offered as pitfalls. Pharmaceutical companies are rapidly developing and marketing new therapies. Therefore, updates on the evolving role of NAC as an antidote for acetaminophen poisoning, new psychotropic medications, and new antidotes were included in this article. These pearls, pitfalls, and updates are intended to provide practical information that is readily applicable to the clinical practice of emergency medicine.

Experimental amitriptyline poisoning: treatment of severe cardiovascular toxicity with cardiopulmonary bypass

STUDY OBJECTIVE

To compare cardiopulmonary bypass (CPB) with more conventional therapy in the treatment of severe amitriptyline poisoning.

DESIGN

Prospective, randomized, controlled, laboratory investigation.

INTERVENTIONS

Profound cardiovascular toxicity was induced in 20 anesthetized Yorkshire swine (72 +/- 8.3 kg) by amitriptyline infusion at 0.5 mg/kg/min. Ventilation was adjusted to keep arterial pH at 7.50 +/- 0.05 and the PCO2 at 35 mm Hg. The swine were randomized in a 1:1 ratio to one of two groups, CPB or control. Both groups received amitriptyline infusion until they experienced near-lethal toxicity, defined as a systolic blood pressure below 30 mm Hg for one minute. The control group was then given supportive treatment, including IV fluids, sodium bicarbonate, vasopressors, and standard pharmacologic (advanced cardiac life support) interventions. Control animals failing to respond to supportive measures after five minutes were given open-chest cardiac massage for 30 minutes or until the return of spontaneous circulation. The CPB group received only mechanical support by CPB for 90 to 120 minutes. No sodium bicarbonate, antiarrhythmics, or cardiotonic agents were provided to the CPB group during this resuscitation.

RESULTS

All 20 animals experienced cardiac conduction delays, dysrhythmias, and progressive hypotension within 30 minutes of receiving IV amitriptyline at 0.5 mg/kg/min. The ten swine receiving CPB as treatment for cardiovascular toxicity were able to completely correct the dysrhythmias, cardiac conduction abnormalities, and hypotension produced by the amitriptyline; however, only one of ten control animals could be resuscitated (P = .0001). Nine of ten swine treated with CPB were easily weaned off bypass without any pharmacologic intervention; however, one required norepinephrine to be weaned. All 11 resuscitated swine were able to be salvaged.

CONCLUSION

CPB improved survival in our swine model of severe amitriptyline poisoning.

Extracorporeal bypass for the treatment of verapamil poisoning

A 25-month-old boy ingested six sustained-release verapamil tablets, each containing 240 mg of drug. Charcoal and cathartic were given but were never passed per rectum. Third-degree heart block, hypotension, and hypocalcemia were only transiently responsive to calcium infusions, inotropic agents, and epicardial pacing. Cardiopulmonary arrest with electromechanical dissociation ensued. Standard cardiopulmonary bypass was used to allow sufficient time for liver detoxication. Serum levels of verapamil fell during the bypass procedure, and the patient's cardiac status improved. However, continued absorption of drug after bypass resulted in a level of 4 mg/L, unresponsive circulatory failure, and death. Early, aggressive gut decontamination and the potential value of cardiopulmonary bypass procedures in poisoning that lead to cardiac depression are emphasized.

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.

Effects of several tricyclic antidepressants on the hemodynamics and myocardial contractility of the anesthetized dogs

Cardiovascular effects of several imipramine analogs were investigated in the anesthetized mongrel dogs. Significant reduction in the cardiac output produced by lower doses (2.5 mg/kg, i.v.) of imipramine and 2-OH-DMI was not due to a depression of myocardial contractility. In contrast, 2-OH-imipramine (1.25 mg/kg) and DMI (2.5 mg/kg) significantly reduced contractility within 10 min after i.v. administration; however, significant decrease in the cardiac output did not occur until after 60 min. Higher doses (5 mg/kg) of imipramine, DMI and 2-OH-DMI significantly attenuated cardiac rate, contractility and output within 5 min after i.v. administration. 2-OH-imipramine, 2.5 mg/kg, i.v., depressed contractility and cardiac output to a degree equivalent to that produced by 5 mg/kg of imipramine, DMI and 2-OH-DMI. 3-Chloro-imipramine (5 mg/kg, i.v.) induced decrease in the cardiac output was essentially due to a significant reduction in the heart rate since the effects of this compound on the contractility were transient in nature. 3-Cl-8-OH-metabolite of this compound had no significant effects on the cardiovascular system. The results of this investigation demonstrated that the complex cardiovascular effects of tricyclic antidepressants observed in these studies were perhaps due to a direct and/or autonomically mediated effects on the heart and vasculature. Further, the data support the conclusions that the activity of the parent compounds together with that of the metabolites contributes to overall changes observed. While all the agents are capable of reducing cardiac output, 2-OH-metabolite of imipramine appears to be most toxic on the myocardium and 3-Cl-imipramine possessed only transient effects on the contractile properties.