Open Veterinary Journal, (2025), Vol. 15(7): 3352-3356

Case Report

10.5455/OVJ.2025.v15.i7.47

Lidocaine and remifentanil for ventricular tachycardia suppression in a dog: A case report

Alyssa Brum de Souza Pahim^1*, Giovana Copetti Jung¹, Talita Freitas Alves¹, Maria Eduarda de Moraes Guerra¹, Cristiana Teixeira da Silva¹, Gabriele Marques Lopes¹, Maria Lígia de Arruda Mestieri², João Pedro Scussel Feranti² and Marília Teresa de Oliveira²

¹Graduate Program in Animal Science, Federal University of Pampa, Uruguaiana, Brazil

²Department of Veterinary Medicine, Federal University of Pampa, Uruguaiana, Brazil

*Corresponding Author: Alyssa Brum de Souza Pahim. Graduate Program in Animal Science, Federal University of Pampa, Uruguaiana, Brazil. Email: alyssapahim [at] gmail.com

Submitted: 16/12/2024 Revised: 20/05/2025 Accepted: 20/06/2025 Published: 31/07/2025

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ABSTRACT

Background: Ventricular tachycardia is an arrhythmia that, if not corrected, can lead to reduced ischemic stroke volume and cardiac output, resulting in low tissue perfusion.

Aim: To describe a case of ventricular tachycardia suppression using lidocaine and remifentanil in a dog during the transanesthetic period.

Case Description: An 11-year-old Labrador Retriever dog with intraoral neoplasia was referred for hemimandibulectomy. Preanesthetic evaluation and complementary diagnostic tests revealed the presence of splenic neoplasia along with paroxysmal ventricular tachycardia. The preanesthetic medication was methadone, and the patient was induced into general anesthesia using propofol. During the transanesthetic period, anesthesia was maintained with sevoflurane and continuous infusion of lidocaine and remifentanil. Throughout the procedure, the patient remained in sinus tachycardia without any arrhythmic events.

Conclusion: The arrhythmias on electrocardiogram during the transanesthetic period highlight the effective control of paroxysmal ventricular tachycardia through the use of lidocaine and remifentanil infusion.

Keywords: Arrhythmia treatment; Dog; Lidocaine; Remifentanil.

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Introduction

Ventricular tachycardia is defined as a rhythm originating from ventricular cells that exceeds the frequency of the subsidiary pacemaker and reaches a higher heart rate than the sinus rhythm (Santilli, 2018). The frequency of occurrence of tachyarrhythmia determines its classification as sustained or non-sustained, repetitive, permanent, or paroxysmal. The latter is characterized by abrupt onset and cessation (Mavropoulou, 2018; Santilli, 2018).

Ventricular arrhythmias are commonly diagnosed as electrocardiographic changes in dogs during routine veterinary practice. A study involving 1201 dogs showed that 11.2% of dogs presented with ventricular arrhythmia, with 67.7% showing ventricular tachycardia (Noszcyk-Nowak et al., 2017). The main causes associated with the onset of monomorphic ventricular tachycardias include cardiomyopathies, such as dilated and hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, myocardial ischemia, and systemic diseases (Santilli, 2018). The presence of ventricular tachyarrhythmias associated with systemic diseases is often related to the release of cardiogenic catecholamines, which promote the occurrence of rhythm disturbances. Gastric volvulus, pyometra, and splenic neoplasms are the most common diseases associated with the appearance of this type of arrhythmia (Tilley and Goodwin, 2002).

Early diagnosis of this type of arrhythmia before the transanesthetic period is crucial because it can influence the anesthesiologist’s decision-making when preparing the anesthetic protocol to be used. Given the main consequence of disorganized depolarization of ventricular cells, such as tachycardia, the use of drugs that cause positive chronotropy and/or increased afterload can harm cardiac tissue (Santilli, 2018). For example, dissociative anesthetics such as ketamine, due to their sympathomimetic action, can lead to an increase in heart rate. This effect further increases the myocardium’s oxygen demand, reduces diastolic time, and consequently reduces ventricular filling time and coronary blood flow (Hamilton, 2024).

In addition to this drug class, the use of alpha-2 receptor agonists such as dexmedetomidine can also cause harm if included in the anesthetic protocol for animals with ventricular tachyarrhythmias. The increased peripheral vascular resistance caused by these medications leads to hypertension and increased afterload, which in turn increases cardiac workload. Therefore, all these factors that may result from the incorrect choice of drugs can lead to ventricular fibrillation, heart failure, and irreversible myocardial ischemia (Santilli, 2018; Creighton and Lamont, 2024). Regardless of the mechanism responsible for the onset of these arrhythmias, treatment is recommended for patients with hemodynamic repercussions, such as altered systolic blood pressure, or clinical signs, such as syncope and fatigue. In general, in systemic cases, removal of the underlying cause typically results in control of the arrhythmias. In other cases, the administration of control drugs is necessary (Santilli, 2018).

Lidocaine, a local anesthetic from the amino-amide family, is widely used for peripheral nerve block but is also considered a class I antiarrhythmic drug, acting by blocking sodium channels (Garcia, 2024). When used systemically, by reducing the entry of sodium into cardiomyocytes, it prevents cellular membrane depolarization and, consequently, the passage of the action potential. Due to its ability to increase the cardiac refractory period, it is frequently administered in cases of tachyarrhythmias (Miller and Flaherty, 2017; Güller et al., 2023).

Considering the increase in heart rate during ventricular tachycardia, the administration of drugs that increase parasympathetic tone is beneficial (Miller and Flaherty, 2017). Remifentanil, an ultra-short-acting μ opioid, is commonly used during surgery for its analgesic potential. However, reducing potassium efflux in cardiac cells prolongs the action potential and delays ventricular repolarization, contributing to a decrease in heart rate (Simon and Lizarraga, 2024). Furthermore, studies have shown that this drug also significantly prolongs the conduction time in specialized cells of the atrioventricular node, increasing its refractoriness, and it has cardioprotective effects in cases of ventricular arrhythmias (Luna-Ortiz et al., 2009; Zaballos et al., 2009).

In light of the above-mentioned information, the present report aimed to describe the transanesthetic management of a dog with a prior diagnosis of paroxysmal ventricular tachycardia.

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Case Details

An 11-year-old male Labrador Retriever weighing 23.1 kg was admitted to a Veterinary University Hospital with the owner’s primary complaint of a rapidly growing mass in the mandibular region, with a recent onset of drainage of bloody secretion originating from the oral cavity, with the clinical suspicion of intraoral melanoma. At the hospital’s clinical department, anamnesis and physical examination were performed, revealing normal heart auscultation and a heart rate (HR) of 152 bpm. At abdominal palpation, the clinician noted increased and firm consistency in certain areas of the splenic parenchyma. After a suspected diagnosis of intraoral neoplasm involving the mandibular bone tissue, surgical treatment of hemimandibulectomy was recommended. Complementary exams were then requested to investigate metastasis, including thoracic radiograph, abdominal ultrasound, as well as hematological tests, and electrocardiography, and the patient was referred for preanesthetic evaluation.

During the preanesthetic physical examination, the patient showed normochromic mucous membranes, a capillary refill time of one second, a normokinetic femoral pulse, adequate hydration status, arrhythmic heart auscultation, and no murmurs. HR remained at 152 bpm with panting and activity. Pulmonary metastasis screening via radiography was negative, but abdominal ultrasound revealed a finding suggestive of splenic neoplasm. The erythrogram showed a hematocrit of 23%, and a blood transfusion bag was requested in case a transfusion was required during the surgery. Additionally, leukocytosis (33,800/l) was observed due to neutrophilia (30,420 segmented neutrophils/l) on the leukogram. Electrocardiographic examination confirmed unifocal paroxysmal ventricular tachycardia, characterized by the presence of capture and fusion complexes and a heart rate of 176 bpm (Fig. 1). Therefore, after analyzing the findings from the anamnesis, physical examination, and complementary tests, the patient was classified as American Society of Anesthesiologists (ASA) III according to the ASA physical status classification.

Fig. 1. Preanesthetic electrocardiogram of an 11-year-old male lLabrador Retriever with intraoral melanoma showing sets of premature ventricular complexes.

For preanesthetic medication, the patient received methadone (0.3 mg/kg, IM) and was induced into general anesthesia with propofol (4.6 mg/kg, IV). After the loss of palpebral reflexes and mandibular tone, the patient was intubated, and sevoflurane diluted in 100% oxygen was administered via a calibrated vaporizer for the maintenance of anesthesia. The patient was then positioned in the right lateral recumbent position, and surgical preparation was started. To ensure intraoperative analgesia, continuous infusion (CI) of lidocaine (50 mcg/kg/minute), preceded by a bolus of 1 mg/kg, IV, and remifentanil (5 mcg/kg/hour), was initiated. Approximately 45 minutes after the start of the CI, the hemimandibulectomy procedure was initiated. Vital parameters, including HR, respiratory rate, end-tidal carbon dioxide, systolic, diastolic, and mean blood pressure obtained by the oscillometric method [systolic blood pressure, diastolic blood pressure, and mean arterial pressure (MAP), respectively], were continuously monitored using a multiparameter monitor.

Immediately after anesthesia induction and the start of the CI, the patient’s HR was 150 bpm, remaining between 125 and 150 bpm until the beginning of the surgical procedure, with a sinus rhythm. At certain points during the transoperative period, the remifentanil dose needed to be adjusted due to signs of nociception, such as an increase in MAP ranging from 5 to 15 mcg/kg/hour. The HR, MAP, and remifentanil dosage parameters recorded during the procedure are shown in Figure 2. The patient maintained an average HR of 114 bpm, without presenting arrhythmias on the electrocardiogram throughout the operation.

The anesthetic and surgical procedure lasted approximately 4 hours, and the patient was extubated approximately 4 minutes after discontinuation of general anesthetic. Postoperative analgesia included morphine (0.4 mg/kg, IM), dipyrone (25 mg/kg, IV), and meloxicam (0.2 mg/kg, IV). A postoperative electrocardiogram was not performed to monitor arrhythmias. However, the patient showed no clinical signs of cardiovascular decompensation and was discharged 2 days after surgery.

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Discussion

A study conducted by Noszczyk-Nowak et al. (2017) demonstrated that male dogs are more predisposed to developing pathological arrhythmias, with the Labrador Retriever breed being the third most affected. Additionally, gender can also be a predisposing factor. Studies have shown that males have a higher prevalence of ventricular arrhythmias and heart disease diagnoses (Noszczyk-Nowak et al., 2017; Baisan et al., 2021). Age is also an important factor, as ventricular arrhythmias are more common in animals aged 6–10 years or older (Noszczyk-Nowak et al., 2017).

The HR of dogs is a parameter associated with body weight and animal size. A study conducted by Hezzell and colleagues (2013) showed that large breeds, such as Labrador Retrievers, tend to have a lower HR compared to small breeds. The same study observed an HR of approximately 100 bpm in Labradors in an outpatient setting. These results are in contrast with those recorded in the patient in the present report, as the preoperative HR variation was 150–170 bpm.

The arrhythmic condition presented by the patient in the preoperative period, characterized as ventricular tachycardia, is a common finding in dogs with splenic masses. A study by Keyes et al. (1993) observed ventricular arrhythmias in 12 of 38 dogs diagnosed with hemoperitoneum due to splenic neoplasia and in 4 of 33 animals without hemoperitoneum. Additionally, Michael et al. (2023), studying dogs undergoing splenectomy due to a diagnosis of splenic neoplasm, concluded that dogs with low hematocrit levels have an increased risk of developing ventricular arrhythmias. Furthermore, the presence of leukocytosis due to neutrophilia also predisposes to the development of ventricular tachyarrhythmias, as these contribute to the development of reperfusion injury in the myocardium (Marino et al., 1994).

The evaluation of ventricular tachycardias, for diagnostic purposes, involves checking the morphology of the QRS complexes on the electrocardiographic trace and their frequency of occurrence (Tilley and Goodwin, 2002). The preoperative electrocardiographic trace of the dog in the present report showed bizarre QRS complexes of the same morphology, indicating depolarization from the same ventricular region, which, in turn, can be interpreted as less dangerous for the patient, characterizing the arrhythmia as monomorphic (Tilley and Goodwin, 2002; Santilli, 2018).

It is also possible to determine the origin of ectopic ventricular beats based on the conformation of the QRS complexes, defining the pattern as resembling those of left or right bundle branch block, thereby determining the origin of the ventricular focus (Mavropoulou, 2018). The pattern presented by the patient revealed a possible arrhythmic focus originating in the right ventricle, which remained the primary initiator of the arrhythmic beats.

The diagnosis of paroxysmal monomorphic ventricular tachycardia involves the occurrence of a series of ectopic beats for less than 30 seconds, sometimes intercalated with the presence of sinus rhythm, as shown in Figure 1. In most cases, these arrhythmias have a sudden onset, as well as a sudden termination. In some cases, the ectopic beats that initiate these tachycardias may show different configurations, indicating that the activating mechanism of the arrhythmia is not the same as the maintaining mechanism (Tilley and Goodwin, 2002; Santilli, 2018).

Fig. 2. Heart rate (HR), mean arterial pressure (MAP), and remifentanil rate parameters recorded during the intra-anesthetic period of canine undergoing hemimandibulectomy. (*Start of the surgical procedure; Arrow: End of surgery).

Despite the various predisposing factors that likely contributed to the occurrence of paroxysmal ventricular tachycardia diagnosed in the preoperative period, the drugs used during anesthesia helped control the tachyarrhythmia during this time. Reports from human medicine describe the conversion of supraventricular arrhythmia to sinus rhythm after the administration of remifentanil combined with propofol (Choi and Jee, 2014). A study in dogs that received CI of remifentanil alongside digoxin infusion, aimed at inducing ventricular arrhythmias, revealed that the opioid demonstrated antiarrhythmic and cardioprotective effects (Luna-Ortiz et al., 2009). Zaballos and colleagues (2009) studied the effects of remifentanil on cardiac electrophysiology in swine models and observed depression of sinus node function and an increase in the refractory period of the atrioventricular node cells, which contributed to a decrease in heart rate during the transoperative period, compared to baseline, and may explain its contribution to arrhythmia control.

Furthermore, lidocaine administered via continuous infusion during the transanesthetic period may also have helped to terminate the arrhythmia during this time. This drug, considered a class IB antiarrhythmic, works by blocking sodium ion channels, leading to a reduction in cardiac automaticity, depolarization rate, and an increase in the refractory period, with this effect being particularly evident in ventricular cardiomyocytes (Santilli, 2018; Güller et al., 2023). Bruchim et al. (2012), when performing a bolus of lidocaine (2 mg/kg) followed by a CI of 0.05 mg/kg/minute before correcting gastric volvulus in dogs, demonstrated that, in the postoperative period, animals in the control group (who did not receive lidocaine) had a significantly higher incidence of premature ventricular complexes and ventricular tachycardia compared to the treated group. In light of these findings, along with the reported effects of remifentanil, the control of arrhythmia in patients described during transanesthetic periods was clarified.

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Conclusion

Despite the elevated heart rate compared to the breed’s normal standard, the absence of ectopic beats and bizarre QRS complexes on the electrocardiographic trace during the transanesthetic period highlights the effective control of the paroxysmal ventricular tachycardia through the use of lidocaine and remifentanil infusion. The anesthetic management enabled the safe completion of the surgical procedure.

Conflict of interest

The authors declare no conflict of interest.

Funding

This research received no specific grant.

Author’s contributions

T.F.A., M.E.M.G., M.L.A.M., C.T.S., and J.P.S.F. executed and conducted the case in the hospital routine; A.B.S.P. and G.C.J. did the manuscript writing and preparation; G.M.L. did the manuscript formatting; M.T.O. did the manuscript revision.

Data availability

All data were provided in the manuscript.

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