Nifekalant Versus Amiodarone in the Treatment of Cardiac Arrest: an Experimental Study in a Swine Model of Prolonged Ventricular Fibrillation

2024 RECOVER Guidelines: Advanced Life Support. Evidence and knowledge gap analysis with treatment recommendations for small animal CPR

OBJECTIVE

To systematically review the evidence and devise clinical recommendations on advanced life support (ALS) in dogs and cats and to identify critical knowledge gaps.

DESIGN

Standardized, systematic evaluation of literature pertinent to ALS following Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Prioritized questions were each reviewed by Evidence Evaluators, and findings were reconciled by ALS Domain Chairs and Reassessment Campaign on Veterinary Resuscitation (RECOVER) Co-Chairs to arrive at treatment recommendations commensurate to quality of evidence, risk:benefit relationship, and clinical feasibility. This process was implemented using an Evidence Profile Worksheet for each question that included an introduction, consensus on science, treatment recommendations, justification for these recommendations, and important knowledge gaps. A draft of these worksheets was distributed to veterinary professionals for comment for 4 weeks prior to finalization.

SETTING

Transdisciplinary, international collaboration in university, specialty, and emergency practice.

RESULTS

Seventeen questions pertaining to vascular access, vasopressors in shockable and nonshockable rhythms, anticholinergics, defibrillation, antiarrhythmics, and adjunct drug therapy as well as open-chest CPR were reviewed. Of the 33 treatment recommendations formulated, 6 recommendations addressed the management of patients with nonshockable arrest rhythms, 10 addressed shockable rhythms, and 6 provided guidance on open-chest CPR. We recommend against high-dose epinephrine even after prolonged CPR and suggest that atropine, when indicated, is used only once. In animals with a shockable rhythm in which initial defibrillation was unsuccessful, we recommend doubling the defibrillator dose once and suggest vasopressin (or epinephrine if vasopressin is not available), esmolol, lidocaine in dogs, and/or amiodarone in cats.

CONCLUSIONS

These updated RECOVER ALS guidelines clarify the approach to refractory shockable rhythms and prolonged CPR. Very low quality of evidence due to absence of clinical data in dogs and cats continues to compromise the certainty with which recommendations can be made.

Effect of Time to Treatment With Antiarrhythmic Drugs on Return of Spontaneous Circulation in Shock-Refractory Out-of-Hospital Cardiac Arrest

Background

The effects of amiodarone and lidocaine on the return of spontaneous circulation (ROSC) in relation to time to treatment in patients with out‐of‐hospital cardiac arrest is not known. We conducted a post hoc analysis of the ROC ALPS (Resuscitation Outcomes Consortium Amiodarone, Lidocaine, Placebo) randomized controlled trial examining the association of time to treatment (drug or placebo) with ROSC at hospital arrival.

Methods and Results

In the trial, adults with nontraumatic out‐of‐hospital cardiac arrest with initial refractory ventricular fibrillation or pulseless ventricular tachycardia after at least 1 defibrillation were randomly assigned to receive amiodarone, lidocaine, or placebo. We used logistic regression to examine the association of time to treatment (911 call to study drug administration) with ROSC. An interaction term between treatment and time to treatment was included to determine the potential effect of time on treatment effects. Overall, 1112 (36.7%) patients had ROSC at hospital arrival (350 in the amiodarone arm, 396 in the lidocaine arm, and 366 in the placebo arm). The proportion of patients who had ROSC decreased as time to drug administration increased, in patients treated with amiodarone (odds ratio, 0.92; 95% CI, 0.90–0.94 per minute increase), lidocaine (odds ratio, 0.95; 95% CI, 0.93–0.96), and placebo (odds ratio, 0.95; 95% CI, 0.93–0.96). With shorter times to drug administration, the proportion with ROSC was higher in amiodarone versus placebo recipients.

Conclusions

The probability of ROSC decreased as time to drug administration increased. The effect of amiodarone but not lidocaine to restore ROSC declined with longer times to drug administration, potentially attributable to its adverse hemodynamic effects.

Anesthesia Protocols used to Create Ischemia Reperfusion Myocardial Infarcts in Swine

The porcine ischemia-reperfusion model is one of the most commonly used for cardiology research and for testing interventions for myocardial regeneration. In creating ischemic reperfusion injury, the anesthetic protocol is important for assuring hemodynamic stability of the animal during the induction of the experimental lesion and may affect its postoperative survival. This paper reviews the many drugs and anesthetic protocols used in recent studies involving porcine models of ischemiareperfusion injury. The paper also summarizes the most important characteristics of some commonly used anesthetic drugs. Literature was selected for inclusion in this review if the authors described the anesthetic protocol used and also reported the mortality rate attributed to the creation of the model. This information is an important consideration because the anesthetic protocol can influence hemodynamic stability during the experimental induction of an acute myocardial infarction, thereby impacting the survival rate and affecting the number of animals needed for each study.

Drugs in cardiac arrest: the rise and fall of antiarrhythmics

Since the publication of 2000 guidelines for resuscitation, amiodarone is considered the antiarrhythmic drug of choice for refractory ventricular fibrillation/pulseless ventricular tachycardia. However, to date there is no proven benefit in terms of neurologically intact survival to hospital discharge. A comprehensive search of the recent literature on amiodarone, nifekalant and lidocaine in cardiac arrest was performed. Amiodarone and nifekalant are superior to lidocaine with regards to the return of spontaneous circulation and survival to hospital admission. Nifekalant shows a trend towards quicker termination of ventricular fibrillation compared to amiodarone. There is great uncertainty about the efficacy of antiarrhythmics in cardiac arrest. Failure to show improvements regarding meaningful survival questions their current use and suggests the need for re-evaluating their place in cardiopulmonary resuscitation.

Does Antiarrhythmic Drug During Cardiopulmonary Resuscitation Improve the One-month Survival: The SOS-KANTO 2012 Study

BACKGROUND

Antiarrhythmic drugs (AAD) are often used for fatal ventricular arrhythmias during cardiopulmonary resuscitation (CPR). However, the efficacy of initial AAD administration during CPR in improving long-term prognosis remains unknown. This study retrospectively evaluated the effect of AAD administration during CPR on 1-month prognosis in the SOS-KANTO 2012 study population.

METHODS AND RESULTS

Of the 16,164 out-of-hospital cardiac arrest cases, 1350 shock-refractory patients were included: 747 patients not administered AAD and 603 patients administered AAD. Statistical adjustment for potential selection bias was performed using propensity score matching, yielding 1162 patients of whom 792 patients were matched (396 pairs). The primary outcome was 1-month survival. The secondary outcome was the proportion of patients with favorable neurological outcome at 1 month. Logistic regression with propensity scoring demonstrated an odds ratio (OR) for 1-month survival in the AAD group of 1.92 (P < 0.01), whereas the OR for favorable neurological outcome at 1 month was 1.44 (P = 0.26).

CONCLUSIONS

Significantly greater 1-month survival was observed in the AAD group compared with the non-AAD group. However, the effect of ADD on the likelihood of a favorable neurological outcome remains unclear. The findings of the present study may indicate a requirement for future randomized controlled trials evaluating the effect of ADD administration during CPR on long-term prognosis.

Meta-analysis of the efficacies of amiodarone and nifekalant in shock-resistant ventricular fibrillation and pulseless ventricular tachycardia

Amiodarone (AMD) and nifekalant (NIF) are used in the treatment of ventricular fibrillation or tachycardia; however, only few studies have been conducted on their efficacies. Therefore, a meta-analysis was conducted. Relevant sources were identified from PubMed, Cochrane Central Register of Controlled Trials, and Igaku Chuo Zasshi. The outcomes were short-term and long-term survival in patients with shock-resistant ventricular fibrillation /pulseless ventricular tachycardia. Thirty-three studies were analysed. The results showed that, compared to the control treatment, AMD did not improve short-term survival (odds ratio (OR): 1.25, 95% confidence interval (CI): 0.91-1.71) or long-term survival (OR: 1.00, 95% CI: 0.63-1.57). However, compared to the control treatment, NIF significantly improved short-term survival (OR: 3.23, 95% CI: 2.21-4.72) and long-term survival (OR: 1.88, 95% CI: 1.36-2.59). No significant difference was observed in short-term survival (OR: 0.85, 95% CI: 0.63-1.15) or long-term survival (OR: 1.25, 95% CI: 0.67-2.31) between AMD- and NIF-treated patients. The results suggest that NIF is beneficial for short-term and long-term survival in shock-resistant ventricular fibrillation/pulseless ventricular tachycardia; however, the efficacy of AMD in either outcome is not clear.

Dantrolene versus amiodarone for cardiopulmonary resuscitation: a randomized, double-blinded experimental study

Dantrolene was introduced for treatment of malignant hyperthermia. It also has antiarrhythmic properties and may thus be an alternative to amiodarone for the treatment of ventricular fibrillation (VF). Aim of this study was to compare the return of spontaneous circulation (ROSC) with dantrolene and amiodarone in a pig model of cardiac arrest. VF was induced in anesthetized pigs. After 8 min of untreated VF, chest compressions and ventilation were started and one of the drugs (amiodarone 5 mg kg⁻¹, dantrolene 2.5 mg kg⁻¹ or saline) was applied. After 4 min of initial CPR, defibrillation was attempted. ROSC rates, hemodynamics and cerebral perfusion measurements were measured. Initial ROSC rates were 7 of 14 animals in the dantrolene group vs. 5 of 14 for amiodarone, and 3 of 10 for saline). ROSC persisted for the 120 min follow-up in 6 animals in the dantrolene group, 4 after amiodarone and 2 in the saline group (n.s.). Hemodynamics were comparable in both dantrolene group amiodarone group after obtaining ROSC. Dantrolene and amiodarone had similar outcomes in our model of prolonged cardiac arrest, However, hemodynamic stability was not significantly improved using dantrolene. Dantrolene might be an alternative drug for resuscitation and should be further investigated.

[Drug Therapy for Shock-Resistant Ventricular Fibrillation: Comparison of Nifekalant and Amiodarone]

Early direct current (DC) shock is the most important therapy for ventricular fibrillation. Following the increased availability of automated external defibrillators (AED), the survival rate of cardiopulmonary arrest patients with ventricular fibrillation has improved. Although patients with shock-resistant ventricular fibrillation require additional antiarrhythmic drug therapy, the optimal protocol has not been established. Nifekalant is a pure potassium channel blocker with a pyrimidinedione structure. Nifekalant was approved in Japan for the treatment of life-threatening ventricular tachyarrhythmias in 1999, and is widely used as a class III antiarrhythmic intravenous drug. Intravenous amiodarone was approved in Japan in 2007, and exhibits various effects on ion channels, receptors, sympathetic activity, and thyroid function. Nifekalant and amiodarone also exhibit many pharmacological and pharmacodynamic differences. As nifekalant has no negative inotropic effect and a rapid action and clearance with a short half-life, it has some advantages over amiodarone for use in cardiopulmonary resuscitation. Indeed, data from clinical and animal studies suggest that nifekalant is superior to amiodarone for resuscitation of cardiopulmonary arrest resulting from shock-resistant ventricular fibrillation. A 300-mg bolus intravenous injection of amiodarone is considered an overdose for resuscitation of shock-resistant ventricular fibrillation. Further clinical studies are required to evaluate the effects of nifekalant compared with amiodarone, and to determine the optimal dose of amiodaone, for resuscitation of shock-resistant ventricular fibrillation.