Comparative effects of sodium bicarbonate and sodium chloride on reversing cocaine-induced changes in the electrocardiogram

The ASAM/AAAP Clinical Practice Guideline on the Management of Stimulant Use Disorder

The American Society of Addiction Medicine/American Academy of Addiction Psychiatry (ASAM/AAAP) Clinical Practice Guideline on the Management of Stimulant Use Disorder provides guidance on evidence-based strategies for the treatment of stimulant use disorders (StUDs), stimulant intoxication, and stimulant withdrawal, as well as secondary and tertiary prevention of harms associated with stimulant use. The Clinical Guideline Committee (CGC) comprised experts from ASAM and AAAP representing a range of clinical settings and patient populations. The guideline was developed following modified GRADE methodology. The process included a systematic literature review as well as several targeted supplemental searches. The CGC utilized Evidence to Decision tables to review available evidence and rate the strength of each recommendation. The clinical practice guideline was revised based on external stakeholder review. Key takeaways included: Contingency management represents the current standard of care for treatment of StUDs; Pharmacotherapies may be utilized off-label to treat StUDs; Acute stimulant intoxication can result in life-threatening complications that should be addressed in an appropriate level of care; Secondary and tertiary prevention strategies should be used to reduce harms related to risky stimulant use.

Acute Cardiovascular Toxicity of Cocaine

Cocaine is one of the most commonly abused drugs and represents a major public health concern. Cocaine users frequently present to the emergency department, with chest pain being the most common presenting complaint. The incidence of acute myocardial infarction in patients with cocaine-associated chest pain is often quoted as 6%, but it is highly variable depending on the included population. Risk assessment can be challenging in these patients; serial assessment of electrocardiograms and troponins is often required. This review focuses on the assessment and management of patients presenting with cocaine-associated chest pain and cardiotoxicity. Specific treatments are discussed, including benzodiazepines, nitroglycerin, calcium channel blockers, and phentolamine, and how treatment priorities differ from patients with noncocaine presentations. The use of beta-blockers in this population remains controversial, and the literature around its use is reviewed. The most recent literature and recommendations for the use of percutaneous coronary intervention and fibrinolytics in cocaine-associated myocardial infarction is discussed as well. Cocaine-associated dysrhythmias are suggested to be the cause of sudden cardiac death in some users. The pathophysiology and evidence-based treatments for dysrhythmias are reviewed. This review provides evidence-based recommendations for the assessment and management of patients presenting with cocaine-associated cardiovascular toxicity.

A Literature Review of the Use of Sodium Bicarbonate for the Treatment of QRS Widening

Sodium bicarbonate is a well-known antidote for tricyclic antidepressant (TCA) poisoning. It has been used for over half a century to treat toxin-induced sodium channel blockade as evidenced by QRS widening on the electrocardiogram (ECG). The purpose of this review is to describe the literature regarding electrophysiological mechanisms and clinical use of this antidote after poisoning by tricyclic antidepressants and other agents. This article will also address the literature supporting an increased serum sodium concentration, alkalemia, or the combination of both as the responsible mechanism(s) for sodium bicarbonate's antidotal properties. While sodium bicarbonate has been used as a treatment for cardiac sodium channel blockade for multiple other agents including citalopram, cocaine, flecainide, diphenhydramine, propoxyphene, and lamotrigine, it has uncertain efficacy with bupropion, propranolol, and taxine-containing plants.

Illicit drugs and cardiac arrhythmias in athletes

The current management of athletes with cardiac arrhythmias has become complicated by the widespread use of illicit drugs, which can be arrhythmogenic.

The World Anti-Doping Agency annually updates a list of prohibited substances and methods banned by the International Olympic Committee that includes different classes of substances namely, anabolic androgenic steroids, hormones and related substances, β2-agonists, diuretics, stimulants, narcotics, cannabinoids, glucocorticosteroids, alcohol, β-blockers and others. Almost all illicit drugs may cause, through a direct or indirect arrhythmogenic effect, a wide range of cardiac arrhythmias (focal or reentry type, supraventricular and/or ventricular) that can even be lethal and which are frequently sport activity related.

A large use of illicit drugs has been documented in competitive athletes, but the arrhythmogenic effect of specific substances is not precisely known. Precipitation of cardiac arrhythmias, particularly in the presence of a latent electrophysiologic substrate including some inherited cardiomyopathies, at risk of sudden death or due to long-term consumption of the substances, should raise the suspicion that illicit drugs may be a possible cause and lead cardiologists to investigate carefully this relationship and appropriately prevent the clinical consequences.

Radiofrequency ablation of drug refractory ventricular tachycardia related to cocaine use: a feasibility, safety, and efficacy study

BACKGROUND

Cocaine use is a known but rare cause of cardiac arrhythmias. Ventricular arrhythmias related to cocaine may not respond to antiarrhythmic drugs and may need treatment with radiofrequency ablation.

OBJECTIVES

We describe the clinical and electrophysiological characteristics of cocaine-related ventricular tachycardia (VT) from a multicenter registry.

METHODS

Subjects presenting with VT related to cocaine use and being considered for radiofrequency ablation have been included in the study. Patients who were refractory to maximal medical therapy underwent radiofrequency ablation of the VT. Clinical, procedural variables, efficacy, and safety outcomes were assessed.

RESULTS

A total of 14 subjects met study criteria (age 44 ± 13, range 18- to 68-year-old with 79% male, 71% Caucasian). MRI showed evidence of scar only in 43% of patients (6/14). The mechanism of VT was focal in 50% (n = 7) and scar related reentry in 50% (n = 7) based on 3D mapping. The mean VT cycle length was 429 ± 96 milliseconds. The site of origin was epicardial in 16% (3/18) of VTs. Most clinical VTs were hemodynamically stable (75%). Mean ejection fraction at the time of admission was 44 ± 14%. Duration of procedure was 289 ± 50 minutes. One subject developed pericardial tamponade requiring drainage. At 18 ± 11 months follow-up, freedom from arrhythmia was seen in 86% (1 case lost to follow-up and 2 died).

CONCLUSION

Radiofrequency ablation is not only feasible but also safe and effective in patients who have drug refractory VT related to chronic cocaine use.

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.

Bicarbonate therapy for unstable propafenone-induced wide complex tachycardia

A previously healthy 73-year-old woman presented to hospital with acute atrial fibrillation. After intravenous procainamide failed to restore sinus rhythm, she was treated with 300 mg of oral propafenone and discharged with a prescription for propafenone and propranolol. Six hours later she took 150 mg of propafenone as prescribed. Within 1 hour she became dyspneic and collapsed. On arrival in hospital she was unconscious, with a wide complex tachycardia and no obtainable blood pressure. After defibrillation and lidocaine, she converted to a wide complex sinus rhythm, but remained profoundly hypotensive despite intravenous epinephrine and dopamine. Hypertonic sodium bicarbonate (HCO3) was administered and, shortly thereafter, her blood pressure increased, her QRS duration normalized and her clinical status improved dramatically. In this case of severe refractory propafenone-related cardiac toxicity, intravenous HCO3 led to a profound clinical improvement. Emergency physicians should be familiar with the syndrome of sodium-channel blocker poisoning and recognize the potentially important role of bicarbonate in its treatment.

Management of cocaine-induced cardiac arrhythmias due to cardiac ion channel dysfunction

Cocaine use is common in many areas of the world, particularly the United States and Western Europe. Toxicity following the use of cocaine is associated with a wide range of clinical features. In this review, we will focus on the cocaine-associated cardiac arrhythmias and, in particular, some of the controversies in their etiology and management. Cocaine can produce arrhythmias either through the production of myocardial ischemia or as a direct result of ion channel alterations. Excessive catecholamines, combined with sodium and potassium channel blockades, give rise to a wide variety of supra-ventricular and ventricular rhythms. The animal and human evidence for ion channel dysfunction is reviewed, and the effects of catecholamines are followed from the cardiac action potential to the development of arrhythmias. Finally, theoretical constructs are combined with existing evidence to develop a rational treatment strategy for patients with cocaine-induced cardiac arrhythmias. In particular, we review the evidence concerning the controversies relating to the use of lidocaine in comparison with sodium bicarbonate, in terms of QRS prolongation secondary to sodium channel blockade.

Case files of the medical toxicology fellowship at the toxikon consortium in Chicago: cocaine-associated wide-complex dysrhythmias and cardiac arrest - treatment nuances and controversies

A 19-year-old woman was brought by ambulance to the emergency department (ED) from a police holding cell. Less than 3 hours earlier, the patient had been a passenger in a car stopped for a traffic violation. As the police officer approached the car, the patient was noted to hurriedly stuff 2 plastic bags containing a white powdery substance into her mouth. On questioning, it was reported that the packets contained cocaine. Less than an hour after being taken to the police station, the patient was witnessed to have a generalized seizure. What is the pharmacological basis of acute cocaine intoxication? What are the cardiovascular manifestations of acute cocaine intoxication? What is the basis for using sodium bicarbonate in cocaine-induced wide-complex dysrhythmias? What is the basis for the use of lidocaine in cocaine-induced wide-complex dysrhythmias? Is there any evidence for the use of amiodarone to treat cocaine-induced wide-complex dysrhythmias?

Mechanisms of acute cocaine toxicity

Patients with acute cocaine poisoning present with life-threatening symptoms involving several organ systems. While the effects of cocaine are myriad, they are the result of a limited number of cocaine-protein interactions, including monoamine transporters, neurotransmitter receptors and voltage-gated ion channels. These primary interactions trigger a cascade of events that ultimately produce the clinical effects. The purpose of this article is to review the primary interactions of cocaine and the effects that these interactions trigger. We also describe the progression of symptoms observed in cocaine poisoning as they relate to serum cocaine concentrations.

Managing cardiovascular collapse in severe flecainide overdose without recourse to extracorporeal therapy

Flecainide overdose can rapidly result in profound cardiovascular collapse, and is associated with a relatively high mortality. A case is described where a woman with major toxicity and high serum levels was managed without recourse to invasive modalities such as cardiopulmonary bypass or extracorporeal therapies. Hypertonic sodium bicarbonate is recognized as effective therapy for hypotension and arrhythmias. More recent case reports have concentrated on the use of cardiopulmonary bypass. In this report and other reports describing successful resuscitation, the total dose of sodium bicarbonate is conspicuously higher than in reports describing extracorporeal interventions. Sodium bicarbonate should be given early in the resuscitation, and re-administered as frequently as required, targeting an alkaline pH and improved cardiac output, while accepting hypernatraemia. This case demonstrates the maxim that the correct dose of hypertonic sodium bicarbonate is 'enough'. Cardiopulmonary bypass support can be considered as a salvage therapy.

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.

QT prolongation through hERG K+ channel blockade: Current knowledge and strategies for the early prediction during drug development

Prolongation of the QT interval of the electrocardiogram is a typical effect of Class III antiarrhythmic drugs, achieved through blockade of potassium channels. In the past decade, evidence has accrued that several classes of drugs used for non-cardiovascular indications may prolong the QT interval with the same mechanism (namely, human ether-a-go-go-related gene (hERG) K(+) channel blockade). The great interest in QT prolongation is because of several reasons. First, drug-induced QT prolongation increases the likelihood of a polymorphous ventricular arrhythmia (namely, torsades de pointes, TdP), which may cause syncope and degenerate into ventricular fibrillation and sudden death. Second, the fact that several classes of drugs, such as antihistamines, fluoroquinolones, macrolides, and neuroleptics may cause the long QT syndrome (LQTS) raises the question whether this is a class effect (e.g., shared by all agents of a given pharmacological class) or a specific effect of single agents within a class. There is now consensus that, in most cases, only a few agents within a therapeutic class share the ability to significantly affect hERG K(+) channels. These compounds should be identified as early as possible during drug development. Third, QT prolongation and interaction with hERG K(+) channels have become surrogate markers of cardiotoxicity and have received increasing regulatory attention. This review briefly outlines the mechanisms leading to QT prolongation and the different strategies that can be followed to predict this unwanted effect. In particular, it will focus on the approaches recently proposed for the in silico screening of new compounds.

Electrophysiologic and Hemodynamic Effects of Sodium Bicarbonate in a Canine Model of Severe Cocaine Intoxication

OBJECTIVE

Cocaine toxicity causes myocardial depression, malignant dysrhythmias, and sudden death, partially due to cocaine-related myocardial sodium channel blockade. Because of cocaine's ability to block cardiac sodium channels, sodium bicarbonate (NaHCO3) has been proposed as an antidote. The hypothesis of this study was that NaHCO3 would correct cocaine-induced conduction abnormalities and resultant hemodynamic compromise in an animal model simulating severe cocaine intoxication.

METHODS

DESIGN

Prospective, controlled, experimental study in which 15 anesthetized dogs were given three successive boluses of cocaine (7 mg/kg) and then randomized to receive NaHCO3, 2 mEq/kg (n = 8) or placebo (n =7).

MEASUREMENTS

Arterial, left ventricular, and pulmonary artery pressures; cardiac output (CO); electrocardiogram (ECG); blood gases; and serum concentrations of cocaine were measured at baseline, at fixed time intervals after each bolus of cocaine, and then after administration of NaHCO3 or placebo. Statistical significance was determined by analysis of variance (ANOVA) for repeated measures.

RESULTS

Seven dogs experienced significant arrhythmias, including VT, pulseless electrical activity, and third-degree atrioventricular block; 2 of these dogs expired prior to receiving NaHCO3 and were excluded. Immediately after administering NaHCO3, QRS duration decreased by 30% (p < 0.001), returning to baseline more quickly than in the control group. This effect was associated with a brief 30% decrease in MAP (p = NS). After NaHCO3, CO increased 78% and remained increased for 5 min (p < 0.007). One dog converted from complete heart block to sinus rhythm shortly after NaHCO3 administration.

CONCLUSIONS

NaHCO3 improved ECG changes secondary to cocaine toxicity and improved myocardial function.

Safety of non-antiarrhythmic drugs that prolong the QT interval or induce torsade de pointes: an overview

The long and growing list of non-antiarrhythmic drugs associated with prolongation of the QT interval of the electrocardiogram has generated concern not only for regulatory interventions leading to drug withdrawal, but also for the unjustified view that QT prolongation is usually an intrinsic effect of a whole therapeutic class [e.g. histamine H(1) receptor antagonists (antihistamines)], whereas, in many cases, it is displayed only by some compounds within a given class of non-antiarrhythmic drugs because of an effect on cardiac repolarisation. We provide an overview of the different classes of non-antiarrhythmic drugs reported to prolong the QT interval (e.g. antihistamines, antipsychotics, antidepressants and macrolides) and discusses the clinical relevance of the QT prolonging effect. Drug-induced torsade de pointes are sometimes considered idiosyncratic, totally unpredictable adverse drug reactions, whereas a number of risk factors for their occurrence is now recognised. Widespread knowledge of these risk factors and implementation of a comprehensive list of QT prolonging drugs becomes an important issue. Risk factors include congenital long QT syndrome, clinically significant bradycardia or heart disease, electrolyte imbalance (especially hypokalaemia, hypomagnesaemia, hypocalcaemia), impaired hepatic/renal function, concomitant treatment with other drugs with known potential for pharmacokinetic/pharmacodynamic interactions (e.g. azole antifungals, macrolide antibacterials and class I or III antiarrhythmic agents). This review provides insight into the strategies that should be followed during a drug development program when a drug is suspected to affect the QT interval. The factors limiting the predictive value of preclinical and clinical studies are also outlined. The sensitivity of preclinical tests (i.e. their ability to label as positive those drugs with a real risk of inducing QT pronglation in humans) is sufficiently good, but their specificity (i.e. their ability to label as negative those drugs carrying no risk) is not well established. Verapamil is a notable example of a false positive: it blocks human ether-a-go-go-related (HERG) K(+) channels, but is reported to have little potential to trigger torsade de pointes. Although inhibition of HERG K(+) channels has been proposed as a primary test for screening purposes, it is important to remember that several ion currents are involved in the generation of the cardiac potential and that metabolites must be specifically tested in this in vitro test. At the present state of knowledge, no preclinical model has an absolute predictive value or can be considered as a gold standard. Therefore, the use of several models facilitates decision making and is recommended by most experts in the field.

Cocaine-induced channelopathies: emerging evidence on the multiple mechanisms of sudden death

Sudden death due to cocaine in the absence of myocardial infarction has been attributed to the precipitation of life-threatening arrhythmias not unlike that due to antiarrhythmic drugs. Cocaine is a slow on-off sodium blocker and a fast on-off potassium blocker. Effects on repolarization are biphasic: At low concentrations, cocaine delays ventricular recovery, whereas at higher levels, cocaine hastens it. Two distinct clinical profiles emerge from case reports of electrocardiographically documented life-threatening arrhythmias attributed to cocaine. The first is monomorphic slow ventricular tachycardia or idioventricular rhythm that occurs in overdose situations and appears to reflect excessive sodium channel block; it may respond to sodium bicarbonate. The second is torsade de pointes that occurs in recreational users who have underlying risks for this tachycardia (such as fully or partially expressed congenital long QT syndrome) and reflects potassium channel blockade. These clinical observations can be explained by recent findings regarding the electrophysiologic effects of cocaine. Other patterns of severe arrhythmias due to cocaine may yet emerge.