Hypertonic sodium chloride and lidocaine in a case of imipramine intoxication

Successful Outcome Following Intravenous Lipid Emulsion Rescue Therapy in a Patient with Cardiac Arrest Due to Amitriptyline Overdose

BACKGROUND The management of patients with tricyclic antidepressant drug overdose can be a challenge for the emergency department physician. Tricyclic antidepressants block alpha-adrenergic receptors and the anticholinergic effects may lead to cardiotoxicity, resulting in arrhythmias and hypotension that can lead to patient mortality. This report is of a case of a 28-year-old woman who presented with cardiac arrest due to amitriptyline overdose and who responded to intravenous lipid emulsion (ILE) therapy. CASE REPORT A 28-year-old woman was admitted to the emergency department with amitriptyline overdose. She suffered a cardiac arrest followed by cardiovascular and neurological complications. Hypotension and lack of a pulse did not respond to treatment with high-dose sodium, but she stabilized following treatment with ILE. The prompt response from the emergency team guaranteed rapid intervention that may have influenced the successful results. CONCLUSIONS Despite the frequency and severity of poisoning with tricyclic antidepressants, there is little consensus among physicians regarding patient management. This case showed the successful use of ILE as rescue therapy in a patient in cardiac arrest following amitriptyline overdose. However, the successful outcome obtained in this case is not a recommendation for the use of ILE as a first-line treatment for the management of patients with tricyclic antidepressant drug overdose. Controlled clinical studies are required to evaluate the safety and efficacy of ILE in the management of tricyclic antidepressant drug overdose.

Treatment of patients with cocaine-induced arrhythmias: bringing the bench to the bedside

Widespread use of cocaine and its attendant toxicity has produced a wealth of benchwork studies and small animal investigations that evaluated the effects of cocaine on the cardiovascular system. Despite this wealth of knowledge, very little is known about the frequency or types of arrhythmias in patients with significant cocaine toxicity. The likely aetiologies; catecholamine excess, sodium channel blockade, potassium channel blockade, calcium channel effects, or ischaemia may act alone or in concert to produce a vast array of clinical findings that are modulated by hyperthermia, acidosis, hypoxia and electrolyte abnormalities. The initial paper in the series by Wood & Dargan providing the epidemiological framework of cocaine use and abuse is followed by a detailed review of the electrophysiological effects of cocaine by O'Leary & Hancox. This review is designed to complement the previous papers and focuses on the diagnosis and treatment of patients with cocaine-associated arrhythmias.

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).

Review article: hypertonic saline use in the emergency department

Hypertonic saline (HS) is being increasingly used for the management of a variety of conditions, most notably raised intracranial pressure. This article reviews the available evidence on HS solutions as they relate to emergency medicine, and develops a set of recommendations for its use. To conclude, HS is recommended as an alternative to mannitol for treating raised intracranial pressure in traumatic brain injury. HS is also recommended for treating severe and symptomatic hyponatremia, and is worth considering for both recalcitrant tricyclic antidepressant toxicity and for cerebral oedema complicating paediatric diabetic ketoacidosis. HS is not recommended for hypovolaemic resuscitation.

Reversal of severe tricyclic antidepressant-induced cardiotoxicity with intravenous hypertonic saline solution

A 29-year-old woman ingested 8 g of nortriptyline and presented to the emergency department with coma, hypotension, and widened QRS interval. After intubation, gastric lavage, hyperventilation, and therapy with intravenous normal saline solution, sodium bicarbonate boluses (rapid intravenous push), and high doses of norepinephrine and dopamine, she transiently improved, only to deteriorate on arrival to the ICU. Because her arterial pH was alkalemic at 7.5 at this point, she was given additional sodium in the form of 200 mL of 7.5% NaCl by means of rapid intravenous infusion (intravenous push) to treat hypotension and widening QRS interval with ventricular ectopy. A continuous 12-lead ECG documented narrowing of her QRS interval with concomitant improvement of hypotension within 3 minutes of hypertonic saline solution infusion. Hypertonic saline solution should be considered for wide complex QRS and hypotension caused by tricyclic antidepressant-induced cardiotoxicity that is unresponsive to standard therapies.

Poisoning by sodium channel blocking agents

Poisoning by drugs that block voltage-gated sodium channels produces intraventricular conduction defects, myocardial depression, bradycardia, and ventricular arrhythmias. Human and animal reports suggest that hypertonic sodium bicarbonate may be effective therapy for numerous agents possessing sodium channel blocking properties, including cocaine, quinidine, procainamide, flecainide, mexiletine, bupivacaine, and others.

Membrane stabilising activity: a major cause of fatal poisoning

Many of the agents held responsible for fatal poisoning in England and Wales--particularly dextropropoxyphene, tricyclic antidepressants, beta-adrenergic antagonists, and chlorpromazine--possess membrane stabilising activity (MSA). This pharmacological property, although regarded as being of little importance in therapeutic use, may be responsible for death in more than 30% of fatal poisonings. Awareness of this possibility may lead to greater care in the prescribing of drugs with this property, to the development of safer alternatives, and to more rational therapy of the poisoned patient.

Displacement of nortriptyline and uptake of 14C-lidocaine in the lung after administration of 14C-lidocaine to nortriptyline intoxicated pigs

Six anaesthetized Swedish land-race pigs were intoxicated by an intravenous infusion of nortriptyline-HCl (NT) up to a concentration of 4.58 +/- 0.58 (mean +/- S.E.M.) microM in arterial whole blood. A rapid injection of 2 mg/kg b.wt. lidocaine-HCl in the right atrium was followed by a rise in arterial whole blood concentration of NT up to a maximum of 7.32 +/- 0.28 microM NT. Amount displaced NT from the cardio-pulmonary circulation after the 14C-lidocaine bolus, was calculated to be 0.66 +/- 0.03 mumol. Lung uptake of 14C-lidocaine during first-pass through the lung was not influenced to any statistically signficant degree compared to a control group. Thus, first pass uptake (FPU) was 30 +/- 8 (mean +/- S.E.M.)% and 39 +/- 5% respectively. The duration of the QRS-complex of the ECG was increased (P less than 0.01) during the infusion of NT from 0.07 +/- 0.01 (mean +/- S.E.M.) sec. to 0.14 +/- 0.02 sec. when 250 mg NT-HCl had been administered. The QRS-duration was decreased (P less than 0.01) after the injection of the 14C-lidocaine bolus to 0.09 +/- 0.01 sec. Mean arterial blood pressure and heartrate decreased slightly during the infusion of NT, but did not change immediately after the 14C-lidocaine bolus.