Hemodynamic and electrophysiological actions of cocaine. Effects of sodium bicarbonate as an antidote in dogs

2023 American Heart Association Focused Update on the Management of Patients With Cardiac Arrest or Life-Threatening Toxicity Due to Poisoning: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

In this focused update, the American Heart Association provides updated guidance for resuscitation of patients with cardiac arrest, respiratory arrest, and refractory shock due to poisoning. Based on structured evidence reviews, guidelines are provided for the treatment of critical poisoning from benzodiazepines, β-adrenergic receptor antagonists (also known as β-blockers), L-type calcium channel antagonists (commonly called calcium channel blockers), cocaine, cyanide, digoxin and related cardiac glycosides, local anesthetics, methemoglobinemia, opioids, organophosphates and carbamates, sodium channel antagonists (also called sodium channel blockers), and sympathomimetics. Recommendations are also provided for the use of venoarterial extracorporeal membrane oxygenation. These guidelines discuss the role of atropine, benzodiazepines, calcium, digoxin-specific immune antibody fragments, electrical pacing, flumazenil, glucagon, hemodialysis, hydroxocobalamin, hyperbaric oxygen, insulin, intravenous lipid emulsion, lidocaine, methylene blue, naloxone, pralidoxime, sodium bicarbonate, sodium nitrite, sodium thiosulfate, vasodilators, and vasopressors for the management of specific critical poisonings.

Sodium bicarbonate reverts electrophysiologic cardiotoxicity of ropivacaine faster than lipid emulsions in a porcine model

Ropivacaine has been described as a safer local anaesthetic (LA); however, serious cardiotoxic accidents have been reported. Intravenous-lipid-emulsion (ILE) therapy during LA intoxication seems to act as an antidote. Sodium bicarbonate is the standard treatment for sodium channel blocker drug toxicity. We compared both antidotes on the reversion of electrophysiologic toxicity induced by ropivacaine. Ropivacaine 5 mg kg^-1 was administered in 24 pigs, and 3 min later, the animals received ILE: 1.5 ml kg^-1  + 0.25 ml kg^-1  min^-1 (ILE group); sodium bicarbonate: 2 mEq kg^-1  + 1 mEq kg^-1  h^-1 (NaHCO₃ group); saline solution (CTL group). Electrophysiological parameters were evaluated for 30 min. The area under the curve (AUC) for the first 5 or 30 min was compared between groups. Ropivacaine induced a lengthening of the PR interval by 17% (P = 0.0001), His-ventricle-interval by 58% (P = 0.001), sinus QRS complex by 56% (P = 0.0001), paced QRS at 150 bpm by 257% (P = 0.0001), and at 120 bpm by 143% (P = 0.0001) in all groups. At 5 min after treatment, sinus QRS in the NaHCO₃ group was shorter than that in the CTL group (AUC_QRS5 , P = 0.003) or ILE group (AUC_QRS5 , P = 0.045). During the first minute, seven of the animals in the NaHCO₃ group vs. two in the ILE or 0 in the CTL group recovered more than 30% of the sinus QRS previously lengthened by ropivacaine (P = 0.003). Sodium bicarbonate reversed the electrophysiological toxicity of ropivacaine faster than ILE and control groups.

Cannabis, cocaine, methamphetamine, and opiates increase the risk of incident atrial fibrillation

AIMS

Atrial fibrillation (AF) is now regarded as a preventable disease, requiring a search for modifiable risk factors. With legalization of cannabis and more lenient laws regarding the use of other illicit substances, investigation into the potential effects of methamphetamine, cocaine, opiate, and cannabis exposure on incident AF is needed.

METHODS AND RESULTS

Using Office of Statewide Health Planning and Development databases, a longitudinal analysis was performed of adult Californians ≥18 years of age who received care in an emergency department, outpatient surgery facility, or hospital from 1 January 2005 to 31 December 2015. Associations between healthcare coding for the use of each substance and a new AF diagnosis were assessed. Among 23,561,884 patients, 98 271 used methamphetamine, 48 701 used cocaine, 10 032 used opiates, and 132 834 used cannabis. Of the total population, 998 747 patients (4.2%) developed incident AF during the study period. After adjusting for potential confounders and mediators, use of methamphetamines, cocaine, opiates, and cannabis was each associated with increased incidence of AF: hazard ratios 1.86 [95% confidence interval (CI) 1.81-1.92], 1.61 (95% CI 1.55-1.68), 1.74 (95% CI 1.62-1.87), and 1.35 (95% CI 1.30-1.40), respectively. Negative control analyses in the same cohort failed to reveal similarly consistent positive relationships.

CONCLUSION

Methamphetamine, cocaine, opiate, and cannabis uses were each associated with increased risk of developing incident AF. Efforts to mitigate the use of these substances may represent a novel approach to AF prevention.

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.

Stimulant Drugs of Abuse and Cardiac Arrhythmias

Nonmedical use of prescription and nonprescription drugs is a worldwide epidemic, rapidly growing in magnitude with deaths because of overdose and chronic use. A vast majority of these drugs are stimulants that have various effects on the cardiovascular system including the cardiac rhythm. Drugs, like cocaine and methamphetamine, have measured effects on the conduction system and through several direct and indirect pathways, utilizing multiple second messenger systems, change the structural and electrical substrate of the heart, thereby promoting cardiac dysrhythmias. Substituted amphetamines and cocaine affect the expression and activation kinetics of multiple ion channels and calcium signaling proteins resulting in EKG changes, and atrial and ventricular brady and tachyarrhythmias. Preexisting conditions cause substrate changes in the heart, which decrease the threshold for such drug-induced cardiac arrhythmias. The treatment of cardiac arrhythmias in patients who take drugs of abuse may be specialized and will require an understanding of the unique underlying mechanisms and necessitates a multidisciplinary approach. The use of primary or secondary prevention defibrillators in drug abusers with chronic systolic heart failure is both sensitive and controversial. This review provides a broad overview of cardiac arrhythmias associated with stimulant substance abuse and their management.

Altered cardiac mitochondrial dynamics and biogenesis in rat after short-term cocaine administration

Abuse of the potent psychostimulant cocaine is widely established to have cardiovascular consequences. The cardiotoxicity of cocaine is mainly associated with oxidative stress and mitochondrial dysfunction. Mitochondrial dynamics and biogenesis, as well as the mitochondrial unfolded protein response (UPRmt), guarantee cardiac mitochondrial homeostasis. Collectively, these mechanisms act to protect against stress, injury, and the detrimental effects of chemicals on mitochondria. In this study, we examined the effects of cocaine on cardiac mitochondrial dynamics, biogenesis, and UPRmt in vivo. Rats administered cocaine via the tail vein at a dose of 20 mg/kg/day for 7 days showed no structural changes in the myocardium, but electron microscopy revealed a significant increase in the number of cardiac mitochondria. Correspondingly, the expressions of the mitochondrial fission gene and mitochondrial biogenesis were increased after cocaine administration. Significant increase in the expression and nuclear translocation of activating transcription factor 5, the major active regulator of UPRmt, were observed after cocaine administration. Accordingly, our findings show that before any structural changes are observable in the myocardium, cocaine alters mitochondrial dynamics, elevates mitochondrial biogenesis, and induces the activation of UPRmt. These alterations might reflect cardiac mitochondrial compensation to protect against the cardiotoxicity of cocaine.

Cocaine induced heart failure: report and literature review

Heart failure is a complex clinical syndrome associated with high mortality and morbidity, creating a major public healthcare problem. It has a variety of etiologies, including substance abuse. Cocaine-induced cardiotoxicity is caused by direct effects of inhibition of sodium channels and indirect effects by inhibiting catecholamine uptake leading to increased sympathetic activity. Management is through the cessation of cocaine use and implantation of guideline-directed medical therapy for heart failure with the exception of beta-blockers as their safe usage is still controversial due to the risk of the unopposed alpha-adrenergic activity. Dexmedetomidine (Precedex) and Benzodiazepines (i.e., midazolam) are options for patients that demonstrate signs and symptoms of acute cocaine intoxication. If the actions of benzodiazepines fail to achieve hemodynamic stability, nitroglycerin may be used (especially in patients with cocaine-associated chest pain and hypertension). Cardiac transplantation is recommended for those who have demonstrated severe cardiovascular disease from cocaine. We present a 43-year-old male with a long-standing history of cocaine use who developed cardiomyopathy and severe acute decompensated heart failure found to have an ejection fraction of <20% admitted to the intensive care unit. He required inotropic support with milrinone and mechanical ventilation. He was later extubated and then discharged with an outpatient evaluation for a cardiac transplant.

Sodium bicarbonate administration during in-hospital pediatric cardiac arrest: A systematic review and meta-analysis

BACKGROUND

Current American Heart Association Pediatric Life Support (PLS) guidelines do not recommend the routine use of sodium bicarbonate (SB) during cardiac arrest in pediatric patients. However, SB administration during pediatric resuscitation is still common in clinical practice. The objective of this study was to assess the impact of SB on mortality and neurological outcomes in pediatric patients with in-hospital cardiac arrest.

METHODS

We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials from inception to January 2021. We included studies of pediatric patients that had two treatment arms (treated with SB or not treated with SB) during in-hospital cardiac arrest (IHCA). Risk of bias was assessed using the Newcastle-Ottawa Scale and the certainty of evidence was assessed using GRADE system.

RESULTS

We included 7 observational studies with a total of 4877 pediatric in-hospital cardiac arrest patients. Meta-analysis showed that SB administration during pediatric cardiac resuscitation was associated with a significantly decreased rate of survival to hospital discharge (odds ratio [OR], 0.40; 95% confidence interval [CI], 0.25-0.63, p value = 0.0003). There were insufficient studies for 24-h survival and neurologic outcomes analysis. The subgroup analysis showed a significantly decreased rate of survival to hospital discharge in both the "before 2010" subgroup (OR 0.47; 95% CI 0.30-0.73; p value = 0.006) and the "after 2010" subgroup (OR 0.46; 95% CI 0.25-0.87; p value = 0.02). The certainty of evidence ranged from very low to low.

CONCLUSIONS

This meta-analysis of non-randomized studies supported current PLS guideline that routine administration of SB is not recommended in pediatric cardiac arrest except in special resuscitation situations.

TRIAL REGISTRATION

The protocol was registered with PROSPERO on 8 August 2020 (registration number: CRD42020197837).

Participation of voltage-gated sodium and calcium channels in the acute cardiac effects of toluene

Inhaling solvents can lead to occurrence of cardiac arrhythmias and sudden sniffing death. Mechanisms related to this phenomenon are not fully understood. The purpose of this study was to investigate the effect of acute toluene exposure on heart reactivity to epinephrine and the participation of voltage-gated sodium and calcium channels. We found that acute toluene exposure increased perfusion pressure, left ventricular developed pressure, and heart rate. These actions were inhibited by lidocaine and nifedipine. Our results suggest that acute toluene exposure modify voltage-gated sodium and calcium channel function and expression likely due to a cardiac adrenergic mechanism and these effects could be participating, at least in part, in the presence of cardiac arrhythmias. To our best knowledge, this is the first report to establish a direct participation of voltage-gated Na⁺ and Ca²⁺ channels, toluene and epinephrine on cardiac function in rats.

Cocaine-Associated Myocardial Infarction

Myocardial ischaemia and infarction has become a well-recognized sequelae of cocaine use. The possibility of recent cocaine use should be assessed in patients with potential myocardial ischaemia because the treatment of patients with myocardial ischaemia related to cocaine differs from that of patients with myocardial ischaemia unrelated to cocaine. Patients with cocaine-associated myocardial ischaemia should receive initial treatment with benzodiazepines to decrease central adrenergic stimulation. Aspirin should be used to reduce thrombus formation, and nitroglycerin to reverse coronary vasoconstriction. Patients with continued ischaemia can be treated with either low doses of phentolamine, or verapamil. If ischaemia continues after treatment with these agents mechanical reperfusion or thrombolytic therapy should be considered depending upon the clinical circumstances. Patients with myocardial ischaemia secondary to cocaine should not receive treatment with beta adrenergic antagonists as these agents enhance coronary vasoconstriction thereby worsening ischaemia.

The Cardiovascular Effects of Cocaine

Cocaine is the leading cause for drug-abuse-related visits to emergency departments, most of which are due to cardiovascular complaints. Through its diverse pathophysiological mechanisms, cocaine exerts various adverse effects on the cardiovascular system, many times with grave results. Described here are the varied cardiovascular effects of cocaine, areas of controversy, and therapeutic options.

Assessment and Management of Toxidromes in the Critical Care Unit

The most important diagnostic factor in uncovering a toxic etiology for delirium or critical illness is the clinician's openness to the possibility of its existence. Therefore, a consulting psychiatrist, already prepared to perform the detail-oriented work of sorting out behavioral manifestations of disease, can be a vital asset at the bedside if also attuned to the role of purposeful, accidental, and iatrogenic exposures in the intensive care unit. This article summarizes the presentation, evaluation, and treatment of toxidromes relevant to the work of acute psychosomatic medicine.

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.

Crack cocaine-induced cardiac conduction abnormalities are reversed by sodium bicarbonate infusion

We report a dramatic case of a 19-year-old man with crack cocaine overdose with important clinical complications as cardiac arrest due to ventricular fibrillation and epileptics status. During this intoxication, electrocardiographic abnormalities similar to those found in tricyclic antidepressant poisoning were observed, and they were reversed by intravenous sodium bicarbonate infusion.

Role of voltage-gated sodium, potassium and calcium channels in the development of cocaine-associated cardiac arrhythmias

Cocaine is a highly active stimulant that alters dopamine metabolism in the central nervous system resulting in a feeling of euphoria that with time can lead to addictive behaviours. Cocaine has numerous deleterious effects in humans including seizures, vasoconstriction, ischaemia, increased heart rate and blood pressure, cardiac arrhythmias and sudden death. The cardiotoxic effects of cocaine are indirectly mediated by an increase in sympathomimetic stimulation to the heart and coronary vasculature and by a direct effect on the ion channels responsible for maintaining the electrical excitability of the heart. The direct and indirect effects of cocaine work in tandem to disrupt the co-ordinated electrical activity of the heart and have been associated with life-threatening cardiac arrhythmias. This review focuses on the direct effects of cocaine on cardiac ion channels, with particular focus on sodium, potassium and calcium channels, and on the contributions of these channels to cocaine-induced arrhythmias. Companion articles in this edition of the journal examine the epidemiology of cocaine use (Wood & Dargan) and the treatment of cocaine-associated arrhythmias (Hoffmann).

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.

Patients presenting with acute toxin ingestion

Organ toxicity caused by poisons or drug therapy is diverse and may not be commonly encountered clinically. In general, commonly encountered conditions caused by drug/toxin pharmacology can be classified into 7 categories by shared mechanisms of organ injury. This review of drug/toxin-induced injury discusses drug or toxin-induced pathology that the clinician may encounter and therapeutic approaches to these syndromes.

Severe central nervous system and cardiovascular toxicity in a pediatric patient after ingestion of an over-the-counter local anesthetic

Dibucaine is considered one of the most potent and consequently toxic amide anesthetics available, and despite withdrawal from the US market as a spinal anesthetic, it remains accessible as an over-the-counter preparation in the United States. Dibucaine exposures in children are infrequently encountered, but to date, all reported consequential ingestions have resulted in death. We report the first case of a potentially fatal dibucaine-induced wide-complex arrhythmia in a child who survived her clinical course without sequelae. It is our hope that this report will highlight the toxicity of dibucaine and prompt a review of its over-the-counter status. The rationale and success of a new antidote, 20% lipid emulsion, for the management of local anesthetic toxicity is discussed.

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.

Combined effects of cocaine and nicotine on cardiovascular performance in a canine model

BACKGROUND

With the proliferation of cocaine abuse, increased incidence of catastrophic cardiovascular events such as angina pectoris, myocardial infarction, ventricular arrhythmias, or sudden death are reported. Many of these patients also smoke cigarettes before and after cocaine use, leading to a high frequency of simultaneous exposure to both drugs. Cocaine's and nicotine's independent effects on cardiodynamics are well documented, but combined effects of both on complete cardiovascular hemodynamics remain unknown.

HYPOTHESIS

The study aimed to determine whether these effects are additive, synergistic, or antagonistic and was therefore designed to investigate the cardiovascular changes produced as a result of combined administration of cocaine and nicotine in a canine model.

METHODS

Initially, in phase 1, 30 experiments were performed to study the dose-response curve of both drugs. In phase II and III, 12 dogs were subjected to 30 experiments. In phase II, cocaine was given intravenously (IV) followed by nicotine. In phase III, sequence of drug administration was reversed to study the effects on hemodynamics and coronary artery blood flow reserve.

RESULTS

Hemodynamic parameters observed were Phase I: Dose-response curve established the IV bolus dose of cocaine 2 mg/kg and nicotine 50 microg/kg. Phase II: Cocaine increased heart rate, blood pressure, and dP/dt, but nicotine administration after cocaine produced marked significant synergistic excitatory effects: dP/dt increased from 1,810 +/- 210 to 6,300 +/- 460 (p < 0.003). Phase III: Nicotine significantly increased heart rate, mean arterial pressures, left ventricular end-diastolic pressure, pulmonary artery, pulmonary capillary wedge, and right atrial pressures. Nicotine increased dP/dt (1,810 +/- 192 to 5,000 +/- 160 mmHg/s; p < 0.004). These excitatory effects of nicotine were attenuated by cocaine when administered as a second drug (dP/dt decreased to 1,925 +/- 144 from 5,000 +/- 160 mmHg/s;p < 0.004).

CONCLUSIONS

Cocaine, when administered alone, caused increase in heart rate, blood pressure, and dP/dt, but nicotine showed a significant increase in all the hemodynamic parameters. Both drugs reduced coronary blood flow reserve. In combination, cocaine plus nicotine administration had synergistic excitatory effects in dogs. A reversed drug combination, that is, nicotine plus cocaine, attenuated the excitatory effects of nicotine.

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.

General anaesthesia for the cocaine abusing patient. Is it safe?

BACKGROUND

Commonly, cocaine abusing patient are scheduled for elective surgery with a positive urine test for cocaine metabolites. As many of these patients were clinically non-toxic [normal arterial pressure and heart rate, normothermic, and a normal (or unchanged from previous) ECG, including a QTc interval <500 ms], we have recently proceeded with elective surgery requiring general anaesthesia in this patient group.

METHODS

Forty urine cocaine positive patients were compared with an equal number of drug-free controls in a prospective, non-randomized, blinded analysis. Intraoperative mean arterial blood pressure, ST segment analysis, heart rate and body temperature were recorded and compared.

RESULTS

Cardiovascular stability during and after general anaesthesia in cocaine positive, non-toxic patients was not significantly different when compared with an age and ASA matched drug-free control group.

CONCLUSIONS

These results demonstrate that the non-toxic cocaine abusing patient can be administered general anaesthesia with no greater risk than comparable age and ASA matched drug-free patients.

Effects of Cocaine Intoxication on the Threshold for Stun Gun Induction of Ventricular Fibrillation

OBJECTIVES

This study sought to assess cocaine's effects on Taser-induced ventricular fibrillation (VF) threshold in a pig model.

BACKGROUND

Stun guns are increasingly used by law enforcement officials to restrain violent subjects, who are frequently intoxicated with cocaine and other drugs of abuse. The interaction of cocaine and the stun gun on VF induction is unknown.

METHODS

We tested five adult pigs using a custom device built to deliver multiples of standard neuromuscular incapacitating (NMI) discharge that matched the waveform of a commercially available electrical stun gun (Taser X-26, Taser International, Scottsdale, Arizona). The NMI discharges were applied in a step-up and step-down fashion at 5 body locations. End points included determination of maximum safe multiple, minimum VF-inducing multiple, and ventricular fibrillation threshold (VFT) before and after cocaine infusion.

RESULTS

Standard NMI discharges (x1) did not cause VF at any of the 5 locations before or after cocaine infusion. The maximum safe multiple, minimum VF-inducing multiple, and VFT of NMI application increased with increasing electrode distance from the heart. There was a 1.5- to 2-fold increase in these values at each position after cocaine infusion, suggesting decreased cardiac vulnerability for VF. Cocaine increased the required strength of NMI discharge that caused 2:1 or 3:1 ventricular capture ratios at all of the positions. No significant changes in creatine kinase-MB and troponin-I were seen.

CONCLUSIONS

Cocaine increased the VFT of NMI discharges at all dart locations tested and reduced cardiac vulnerability to VF. The application of cocaine increased the safety margin by 50% to 100% above the baseline safety margin.

ECG Manifestations: The Poisoned Patient

Despite that drugs have widely varying indications for therapeutic use, many unrelated drugs share a common cardiac pharmacologic effect if taken in overdose. The purpose of this article is to group together agents that cause similar electrocardiographic effects,review their pharmacologic actions, and discuss the electrocardiographic findings reported in the medical literature.

Evaluation and Management of the Patient Who Has Cocaine-associated Chest Pain

Patients who have chest pain following the use of cocaine have become more common in emergency departments throughout the United States,with approximately 6% of these patients sustaining an acute MI. The authors have described the rationale for recommending aspirin, benzodiaze-pines, and nitroglycerin as first-line treatments and calcium-channel blockade or phentolamine as possible second-line therapies and have summarized the controversies surrounding the use of fibrinolytic agents. Admission for observation is one reasonable approach to the management of the low-risk cohort. Evaluation for underlying coronary artery disease is reasonable, particularly in patients who have acute MI. Patients who do not have infarction can undergo evaluation for possible coronary artery disease on an outpatient basis. Routine interventions for secondary prophylaxis as well as cocaine rehabilitation should be used in this patient population, because the long-term prognosis seems somewhat dependent upon the ability of the patient to discontinue cocaine use.

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.

The effect of amiodarone pretreatment on survival of mice with cocaine toxicity

INTRODUCTION

Cocaine is a common drug of abuse and use has been associated with ventricular dysrhythmias. Published guidelines suggest that amiodarone is the first line antidysrhythmic for ventricular tachycardia and fibrillation. However, the effects amiodarone in the setting of cocaine toxicity are unknown and unstudied. The purpose of this study was to evaluate the safety and efficacy of amiodarone pretreatment in a murine model of acute cocaine toxicity.

METHODS

This was a randomized, blinded, placebo controlled investigation using male CF-1 mice weighing 29-37 g. First, the safety of an intraperitoneal dose of amiodarone (40 mg/kg) was confirmed in 5 mice. Second, based on preliminary investigations, an approximate intraperitoneal LD50 dose of cocaine (110 mg/kg) was identified and used as the cocaine dose in this study. Animals were then randomized to 2 groups. The control group received 0.5 mL of intraperitoneal 0.9% saline 30 minutes before cocaine. The study group received 40 mg/kg of intraperitoneal amiodarone (40 mg/kg) 30 minutes before cocaine. A blinded observer monitored mice for 2 hours after cocaine administration.

RESULTS

No mice in the amiodarone-only group developed any signs of toxicity or died. In the saline + cocaine group 31/32 (96.9%; 95% CI 83.8 to 99.9) mice seized with a median time to seizure of 2.5 minutes, and 23/32 (71.9%; 95% CI 52.3 to 86.3) died with a median time to death of 5.5 minutes. In the amiodarone + cocaine group 31/33 (93.9%; 95% CI 79.0 to 99.3) mice seized with a median time to seizure of 2.0 minutes, and 24/33 (72.7%; 95% CI 54.5 to 86.7) died with a median time to death of 6.0 minutes. All animals that died did so within 9 minutes. The difference in the proportion of animals dying in the amiodarone + cocaine group compared to the saline + cocaine group was 0.008 (-21 to 22%).

CONCLUSIONS

In this study, pretreatment with amiodarone in cocaine poisoned mice resulted in no change in seizure incidenceor mortality. However, definite conclusions about the reason for these findings cannot be drawn from this model.

Cocaine-associated chest pain

Current estimates establish that more than 30 million people in the United States use cocaine. Cardiovascular complaints commonly occur among patients who present to emergency departments(EDs) after cocaine use, with chest pain the most common complaint in several studies. Although myocardial ischemia and infarction account for only a small percentage of cocaine-associated chest-pain, physicians must understand the pathophysiology of cocaine and appropriate diagnostic and treatment strategies to best manage these patients and minimize adverse outcomes. This article reviews the pharmacology of cocaine, its role in the pathogenesis of chest pain with specific emphasis on inducing myocardial ischemia and infarction, and current diagnostic and management strategies for cocaine-associated chest pain encountered in the ED.

Quality of poisoning management advice in the Monthly Index of Medical Specialties Annual

BACKGROUND

The Monthly Index of Medical Specialties (MIMS) contains Therapeutic Goods Administration-approved product information supplied by manufacturers. It is widely used by health-care professionals but is not specifically designed as a toxicology reference.

OBJECTIVES

To determine how widespread the use of MIMS is as a toxicology reference. To evaluate the quality of poisoning management advice it contains.

METHODS

First, a survey of 500 consecutive calls to the NSW Poison Information Centre (PIC) was undertaken asking health-care workers which toxicology references were consulted prior to calling and which references they would use if the PIC were not available. Second, a consensus opinion for poisoning management was obtained, for 25 medications which are either commonly involved in poisoning or potentially life-threatening in overdose, by review of 5 current toxicology references for contraindicated treatments, ineffective treatments and specific recommended treatments and antidotes. MIMS poisoning management advice was then compared with this toxicology consensus opinion.

RESULTS

In total, 276 doctors and 222 nurses were surveyed. Prior to calling the PIC 22.8% of doctors and 6.8% of nurses consulted MIMS. In total, 25.7% of doctors and 39.6% nurses stated they would use the MIMS for poisoning management advice if the PIC were not available. For the 25 drugs assessed, 14 contained inaccurate poisoning management: 1 recommended ineffective treatments and 14 omitted specific treatments or antidotes.

CONCLUSION

The MIMS is often used as a toxicology reference by physicians prior to calling the PIC. It contains a number of significant inaccuracies pertaining to management of poisonings and should not be used as a primary reference for poisoning advice.

An engineered cocaine hydrolase blunts and reverses cardiovascular responses to cocaine in rats

There is increasing evidence that human plasma butyrylcholinesterase can lower the toxicity of cocaine overdose. Recently, with structure-based protein engineering, we converted this enzyme into a more efficient cocaine hydrolase (CocE). When tested in rats, CocE shortened cocaine's plasma half-life and decreased drug accumulation in heart and brain. Here, we have investigated the potential of CocE to antagonize cardiovascular responses to cocaine. Anesthetized rats were instrumented for continuous recording of blood pressure from the femoral artery. Cocaine (7 mg/kg i.v.) caused blood pressure to rise within 30 s by 25 to 37 mmHg, but pressure returned to baseline within 60 s. These transient pressor responses were prolonged up to 5 min when vagal reflexes were blocked with atropine (1 mg/kg). Under such conditions, pretreatment with CocE (3 mg/kg i.v.) reduced cocaine's pressor effect, whereas delayed treatment with CocE rapidly restored normal mean blood pressure. CocE had no hemodynamic effects in control animals not treated with cocaine. The finding that CocE can oppose pre-established physiologic actions of cocaine suggests that similar or improved hydrolases might help rescue patients from the life-threatening toxicity of drug overdose.

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.

Cocaine and cardiovascular toxicity

Over the past 10 years a great deal has been learned about the cardiovascular effects of cocaine. In particular, the acute effects of cocaine have been studied extensively. Upon acute administration cocaine increases blood pressure and heart rate, primarily through an action on the sympathetic nervous system. Cocaine also suppresses the baroreflex response and vagal tone, further contributing to its effects on heart rate. At the same time cocaine is increasing the work-load on the heart it induces coronary artery vasoconstriction, potentially leading to cardiac ischemia. At higher doses cocaine can depress ventricular function and slow electrical conduction in the heart. Both these effects appear to be mediated by cocaine's local anesthetic action. The effects of cocaine mediated by the sympathetic nervous system are greatly reduced in anesthetized animals. Further, when cocaine is administered repeatedly over a short period of time, acute tolerance can develop to the sympathomimetic effects of cocaine. In contrast, the effects of cocaine mediated by its local anesthetic action do not appear blunted by anesthesia or susceptible to acute tolerance. With chronic administration, higher doses appear to induce tolerance while lower doses may induce sensitization to cocaine's sympathomimetic effects. Cocaine also induces a variety of pathological changes in the heart, including myocardial contraction band necrosis and ventricular hypertrophy. These effects of cocaine on the heart can all contribute to potentially lethal cardiovascular events. In addition to the effects of cocaine alone, the metabolites of cocaine may also contribute to cocaine's cardiovascular toxicity, and both licit and illicit drugs used in combination with cocaine might potentially alter its cardiovascular effects.

Cardiovascular manifestations of substance abuse part 1: cocaine

Substance abuse with cocaine is associated with multiple cardiovascular conditions, including myocardial infarction, dissection, left ventricular hypertrophy, arrhythmias, sudden death, and cardiomyopathy. Cocaine has effects to potentiate the physiologic actions of catecholamines and has direct effects on voltage-dependent sodium ion channels related to local anesthetic properties. The effects of cocaine can be augmented with concomitant alcohol consumption. Acute myocardial ischemia caused by cocaine may be related to in situ thromboisis and/or coronary vasospasm. Treatment strategies for cocaine-induced myocardial infarction would include antiplatelet therapy, thrombolysis, and vasodilators (eg, nitrates, nifedipine). Beta-adrenergic blockers should not be used unless concomitant vasodilator therapy is given.

Cardiovascular disorders associated with cocaine use: myths and truths

Cocaine produces a pattern of cardiovascular responses that are associated with apparent myocardial ischemia, arrhythmias, and other life-threatening complications in some individuals. Despite recent efforts to better understand the causes of cocaine-induced cardiovascular dysfunction, there remain a number of unanswered questions regarding the specific mechanisms by which cocaine elicits hemodynamic responses. This review will describe the actions of cocaine on the cardiovascular system and the evidence for the mechanisms by which cocaine elicits hemodynamic and pathologic responses in humans and animals. The emphasis will be on experimental data that provide the basis for our understanding of the mechanisms of cardiovascular toxicity associated with cocaine. More importantly, this review will identify several controversies regarding the causes of cocaine-induced cardiovascular toxicity that as yet are still debated. The evidence supporting these findings will be described. Finally, this review will outline the obvious deficits in our current concepts regarding the cardiovascular actions of cocaine in hope of encouraging additional studies on this grave problem in our society.

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.

COCAINE USE AND ACUTE MYOCARDIAL INFARCTION

Cocaine use in the United States is widespread, affecting more than 30 million Americans. Although many of these persons do not seek healthcare, the overriding cause for hospitalization is cocaine-associated chest pain. Because only a minority of these patients suffer myocardial injury, it is important to exclude even rarer life-threatening causes for chest pain, such as aortic dissection or pneumothorax. Following that, a thorough knowledge of the pathophysiology and existing literature helps to provide cost-effective care, which focuses resources on those patients most likely to suffer complications. Regardless of the severity of complications, referral to cocaine detoxification programs, counseling, social support, and outpatient follow-up care for modification of cardiac risk factors is a fundamental component of long-term patient care.

Inhibition of human ether-a-go-go potassium channels by cocaine

Cocaine is a potent cardiac stimulant and its use has been linked to life-threatening arrhythmias in humans. A prominent effect of cocaine in the heart is a suppression of the delayed-rectifier potassium current (I(K)) that is important for cardiac repolarization. In this study, cocaine was found to be an inhibitor of HERG channels that underlie the rapidly activating component of I(K). HERG was expressed in tsA201 cells and the whole-cell currents were measured using the patch-clamp technique. HERG currents are inhibited in a dose-dependent fashion with an IC(50) value of 5.6 +/- 0.4 microM. The cocaine inhibition increases over the range of voltages at which the channels activate, indicating that cocaine preferentially binds to open or inactivated channels. At more depolarized potentials, at which the channels are maximally activated, the cocaine inhibition is constant indicating that the binding of the drug is not directly influenced by voltage. Cocaine reduces both the peak tail currents and the instantaneous currents measured by applying voltage steps under conditions where channels are open. The data are consistent with the inhibition of open channels. Cocaine also accelerates the rapid decay of the current at depolarized voltages suggestive of an interaction with inactivated channels. The data indicates that cocaine inhibits the channels by preferentially binding to a combination of open and inactivated states.

Cardiac and hemodynamic assessment of patients with cocaine-associated chest pain syndromes

BACKGROUND

Animal and human experimental studies have yielded conflicted data regarding the effects of cocaine on cardiovascular function. We studied the cardiac and hemodynamic profiles in emergency department chest pain patients following recent cocaine use.

METHODS

After obtaining informed consent, emergency department patients who presented with a chief complaint of chest pain and cocaine use within 24 hours of arrival were prospectively enrolled. All patients underwent a structured 40-item history and physical examination and were placed on the IQ Noninvasive Hemodynamic Surveillance System (Renaissance Technology, Inc., Newton, PA), a validated transthoracic cardiac output monitor. The principal measurements obtained included cardiac output, cardiac index, and stroke volume. Data were analyzed with standard descriptive techniques.

RESULTS

Twenty-seven patients were enrolled (median age, 37 years [range, 23-54]; 74% male). Patients used a mean of $200 worth of cocaine, usually crack (67%). Patients had a history of tobacco use (82%), prior myocardial infarction (33%), and prior cocaine-associated chest pain (67%). The median (interquartile range; IQR) for the hemodynamic parameters were: mean arterial blood pressure 92 mm Hg (IQR 85-100); heart rate 83/min (IQR 72-98); cardiac output 6.9 L/min (IQR 5.1-7.2); cardiac index 3.2 L/min/m2 (IQR 2.4-4.0); stroke volume 78 mL/beat (IQR 64-93).

CONCLUSION

Most emergency department patients with cocaine-associated chest pain have normal cardiac profiles at the time of presentation. The negative inotropic effects of high doses of cocaine observed in animal models do not appear to be present in patients who develop chest pain after using recreational doses of cocaine.

Cocaine abuse: repolarization abnormalities and ventricular arrhythmias

Increased QT and QT dispersion has been linked to arrhythmic death in patients with congenital and acquired long QT syndromes. The repolarization abnormalities were studied in 45 patients with a history of chest pain, somnolence, or disorientation admitted to the hospital for cocaine abuse. Group I was composed of patients with anginal chest pain (n = 23), whereas in group II patients (n = 22), chest pain was absent. Measurements were made of QT and QTc and of QT and QTc dispersion characteristics. Cocaine prolonged the QT, QTc, and QTc dispersion and enhanced the appearance of abnormal U waves. Lethal ventricular arrhythmias were observed in 3 patients. Anginal chest pain may be a marker for myocardial ischemia and, in the presence of abnormal ventricular repolarization, may cause lethal ventricular arrhythmias and sudden death in persons exposed to cocaine.