Hypertonic sodium bicarbonate partially reverses QRS prolongation due to flecainide in rats

Flecainide Toxicity Secondary to Accidental Overdose: A Pediatric Case Report of Two Brothers

Flecainide is a class 1C antiarrhythmic with a narrow therapeutic window and thereby a high-risk medication for causing acute toxicity. Dysrhythmias secondary to flecainide ingestion are often refractory to antiarrhythmics and cardioversion, and patients commonly require extracorporeal support. We review the successful resuscitation of two brothers aged 2 and 4 who presented two years apart with unstable wide-complex tachyarrhythmia suspicious for severe flecainide toxicity. Each patient received sodium bicarbonate and 20% intravenous lipid emulsion with a full recovery. While extracorporeal support is often required following flecainide ingestion, we present two cases where it was avoided due to aggressive multimodal management with sodium bicarbonate, electrolyte repletion, and 20% intravenous lipid emulsion. In addition, avoidance of agitation-induced tachycardia may be beneficial.

Review on Flecainide Poisoning

Flecainide acetate is a Vaughn-Williams class IC antiarrhythmic. It is used mainly for treatment of supraventricular arrhythmias due to reentry and is highly effective in suppressing frequent premature ventricular depolarization and nonsustained ventricular tachycardia (VT). Although less than 1% of drug overdoses are fatal, severe intoxication with Vaughn-Williams class IC antiarrhythmics is associated with average mortality of 22.5% and the rate of mortality after flecainide overdose is approximately 10%. Severe flecainide overdose is frequently fatal because of the rapid onset of hypotension and ventricular arrhythmias. Its cardiotoxicity is mainly due to its sodium and potassium channels blocking effects. Commonly recommended therapies like haemolysis or haemoperfusion is not helpful because of its large volume of distribution. As a result, the treatment goals are to decrease the amount of blockade; correct aggravating conditions for arrhythmias, such as electrolytes disturbances or hypoxia; avoid drugs with sodium channels blocking effects. Recently, there are some successful data on using peripheral cardiopulmonary bypass technique in the treatment of severe flecainide intoxication. This may be a promising treatment option in this type of drug overdose.

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.

Propafenone poisoning--a case report with plasma propafenone concentrations

Propafenone is an anti-arrhythmic drug used in the management of supraventricular and ventricular arrhythmias. It is metabolised through cytochrome P450 2D6 pathways; the major metabolites possess anti-arrhythmic activity. The cytochrome P450 CYP2D6 is coded by more than 70 alleles resulting in great genetic polymorphism of CYP2D6 isoenzymes, and up to 7% of Caucasian population are poor metabolisers. This case report describes a patient with severe overdose of propafenone who presented with coma, seizures and cardiotoxicity. The patient was managed with intravenous glucagon, hypertonic sodium bicarbonate, hypertonic saline and inotropic support. The propafenone and its 5-hydroxypropafenone (5-OHP) metabolite were measured by high-performance liquid chromatography with ultraviolet detection (no assay was available at the time to measure N-despropyl propafenone concentrations). Toxicological screen showed propafenone concentrations at a maximum of 1.26 mg/L at 9-10 h post-presentation, falling to 0.25 mg/L at 27-28 h post-presentation. No propafenone metabolite 5-OHP was detected in any sample analysed. No antidepressant or analgesic drugs were detected in toxicological screen. Propafenone overdose has been reported to be associated with features of severe cardiovascular and CNS toxicity. Aggressive treatment, meticulous monitoring and supportive care was associated with a good outcome in this case.

Electrocardiographic changes in a rare case of flecainide poisoning: a case report

Flecainide is a class Ic anti - arrhythmic drug with sodium channel blocking activities. We report a case of a 57 year - old woman who attempted a suicide by ingesting approximately 1,8 gr of flecainide. On the surface electrocardiogram this results in a large QRS complex and in prolongation of the QTc interval. Overdose with a class Ic drug is very uncommon, its management is difficult and the mortality high.

Because of a hemodynamic instability and in addition to supportive care and antidysrhythmics, she was treated with a high dose of sodium bicarbonate in hypertonic solution; after this infusion the patient's QRS progressive narrowed.

In conclusion, sodium bicarbonate may be useful in the treatment of widened QRS and to stabilize a overdose of class Ic anti - arrhythmic drugs.

Life-Threatening Flecainide Intoxication in a Young Child Secondary to Medication Error

Objective:

To describe a case of life-threatening flecainide intoxication in a toddler, secondary to accidental reversal of syringes used for oral administration.

Case Summary:

A 2-year-old male with a history of a persistent junctional reciprocating tachycardia had been receiving flecainide 4.8 mg/kg/day (1 mL 3 times daily) and nadolol 2 mg/kg/day (5 mL once daily) for 10 months. One morning, 3 hours after the drugs were administered, he became bradycardic (heart rate 50 beats/min) and then presented to the emergency department with vital signs absent. After initial cardiopulmonary resuscitation and epinephrine, he was bradycardic; this was followed by wide-complex tachycardia that converted rapidly to narrow-complex tachycardia after bolus administration of intravenous sodium bicarbonate for suspected flecainide intoxication. Following resuscitation, he remained hemodynamically stable and was discharged in normal sinus rhythm without neurologic sequelae. Drug concentrations obtained at the time of presentation showed a serum concentration of flecainide of 0.668 μg/mL. Drug formulations were also analyzed and found to contain the expected concentration of flecainide.

Discussion:

Literature regarding adverse drug events in the pediatric outpatient population is reviewed, as well as how these risks apply to flecainide, a medication with a low margin of safety. Pediatric experience with flecainide intoxication and sodium bicarbonate administration as an antidote is reviewed. Analysis of the serum drug concentrations demonstrated blood concentrations consistent with syringe reversal, which would have produced a 5-fold flecainide overdose. The Naranjo probability scale indicated a highly probable relationship between flecainide ingestion and the life-threatening event in this case.

Conclusions:

This case of life-threatening flecainide intoxication in a young child, secondary to accidental reversal of medication syringes, underscores the importance of providing parents with accurate dispensing information and labeling medication bottles and syringes in an unambiguous manner.

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.

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.

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.

Sodium bicarbonate to correct widened QRS in a case of flecainide overdose

A 16-yr-old male attempted suicide by ingesting approximately 4000 mg of flecainide. He developed coma, hypotension, and ventricular tachycardia. In addition to supportive care and antidysrhythmics, he received intravenous sodium bicarbonate for the wide complex dysrhythmia. Animal studies and anecdotal human experience have suggested that increasing the extracellular sodium improves cardiac conduction in flecainide toxicity. The patient's QRS narrowed immediately following sodium bicarbonate infusion. Sodium bicarbonate may be useful in the treatment of widened QRS and ventricular ectopy resulting from flecainide toxicity.

The effect of hypertonic sodium bicarbonate on QRS duration in rats poisoned with chloroquine

OBJECTIVE

To determine efficacy of hypertonic sodium bicarbonate in narrowing QRS prolongation produced by chloroquine.

DESIGN

Randomized, controlled animal experiment using an accepted rat model of sodium channel blockade.

METHODS

Hypotension and widening of QRS complexes (lead II) of the ECG were produced in 16 rats by administration of a total of 87 mg/kg chloroquine intravenously over 20 minutes. Eight rats were treated with 6 mL/kg 1 M sodium bicarbonate intravenously over two minutes beginning ten minutes into the chloroquine infusion. Serial measurements of QRS duration and systolic blood pressure were obtained for 30 minutes.

RESULTS

QRS intervals narrowed more rapidly in animals receiving sodium bicarbonate (p = .045), although the difference in mean rate of narrowing between groups was modest at only .23 msec/min. Because of large variances, no statistically significant differences could be demonstrated in systolic blood pressure.

CONCLUSIONS

Hypertonic sodium bicarbonate partially reversed sodium channel blockade and resultant QRS interval prolongation produced by chloroquine in rats. These data should be interpreted with caution, given the need to extrapolate to humans and the modest effect of sodium bicarbonate on QRS narrowing.

Reversal of flecainide-induced ventricular arrhythmia by hypertonic sodium bicarbonate in dogs

Flecainide occasionally produces incessant ventricular tachycardia that is difficult to treat. Reports of uncontrolled clinical studies have suggested a therapeutic role for hypertonic sodium bicarbonate (NaHCO3). To test this observation, spontaneous and pacing-induced arrhythmia canine models were designed. In the spontaneous model, flecainide was infused at 0.5 mg/kg/min until ventricular tachycardia occurred spontaneously. In the pacing-induced model, flecainide was infused at 1.0 mg/kg/min load (0.5 mg/kg/min maintenance) stepwise until the QRS was widened 50%, 75%, and 100%, with programmed ventricular stimulation at each step until ventricular arrhythmia was induced. Dogs who developed spontaneous arrhythmia were treated blindly with three doses of either NaHCO3 (3 mEq/kg/dose, with 1 minute between doses) or normal saline. Dogs who were induced in the second model were treated with the same three doses, 10 minutes apart, with programmed stimulation between each dose. Before unblinding in both protocols, dogs were classified as "responders" or "nonresponders" to therapy. In the spontaneous model, of 14 dogs with spontaneous ventricular tachycardia, all 7 dogs treated with NaHCO3 showed response, compared with only 1 of 7 dogs treated with saline (P < .01). Ventricular QRS complexes/min were reduced by NaHCO3 in that protocol. In the induced arrhythmia protocol, of 14 dogs with inducible arrhythmia, 6 of 7 responded to NaHCO3, and 1 of 7 responded to placebo (P < .05). In both protocols, arterial pH and the serum sodium concentration were increased by NaHCO3 but not by normal saline control treatment. QRS interval duration was shortened by NaHCO3 therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of effect of hypertonic sodium bicarbonate on QRS duration in patients taking therapeutic doses of class IC antiarrhythmic drugs

Hypertonic sodium bicarbonate (HSB) has been reported to reduce the toxicity of Class IC antiarrhythmic agents in rats and, anecdotally, in patients. A pilot study was conducted of the safety and efficacy of HSB for reversing the electrocardiographic effects of therapeutic doses of encainide or flecainide in ten patients taking these drugs for chronic ventricular arrhythmias. Patients had a mean drug-induced QRS prolongation before treatment of 27.6 +/- 8.8%. Each patient received a single dose of HSB 100 mEq or normal saline IV over 5 minutes on two separate occasions. The administration of treatments was blinded and balanced. There were no important side effects of HSB. Venous blood pH, CO2 content and sodium concentration were all significantly increased by HSB in comparison to saline. No differences were found during the 2-hour observation period in the primary endpoint, QRS duration, the PR or QT intervals, or the frequency of premature ventricular beats. It was concluded that HSB 100 mEq does not reduce QRS duration in patients taking therapeutic doses of flecainide or encainide. Because HSB was well tolerated, investigation of its use in higher doses or in patients with overt toxicity due to Class IC drugs is feasible.

Clinical course and outcome in class IC antiarrhythmic overdose

120 cases of class IC antiarrhythmic overdose, including propafenone, flecainide, ajmaline and prajmaline overdose, were evaluated with respect to clinical course, therapy and outcome. Whereas drug overdose in general has an overall mortality of less than 1%, intoxication with antiarrhythmic drugs of class IC was associated with a mean mortality of 22.5%. Nausea, which occurred within the first 30 minutes after ingestion, was the earliest symptom. Spontaneous vomiting probably led to self-detoxication in about half the patients. Cardiac symptoms including bradycardia and, less frequently, tachyrhythmia occurred after about 30 minutes to 2 hours. Therapeutic measures included administration of activated charcoal, gastric lavage and a saline laxative, catecholamines, and in some patients, hypertonic sodium bicarbonate, insertion of a transvenous pacemaker and hemoperfusion. Fatal outcome was mainly due to cardiac conduction disturbances progressing to electromechanical dissociation or asystolia. Resuscitation, which had to be performed in 29 patients, was successful in only two of them. No correlation was found between fatal outcome, the type of antiarrhythmic, and ingested dose. Since a specific treatment is not available and resuscitive procedures including sodium bicarbonate and insertion of a pacemaker are of limited therapeutic value, early diagnosis and primary detoxification are most important for prevention of fatal outcome.