Electrocardiographic evaluation in dogs that underwent pre-anesthesia with dexmedetomidine-methadone and acepromazine-methadone

Abstract

The objective of this study was to compare electrocardiographic changes following the use of dexmedetomidine and acepromazine as pre-anesthetic medication in dogs undergoing ovariohysterectomy (OHE). The dogs were previously evaluated through a general clinical examination, and the main physiological parameters were assessed: heart rate, respiratory rate, rectal temperature, and capillary refill time. They were divided into two groups: (n=16) Group G1: (methadone 0.3 mg/kg + dexmedetomidine 2 μg/kg) and Group G2: (methadone 0.3 mg/kg + acepromazine 0.03 mg/kg). A computerized electrocardiograph (InCardio Agile) was used to acquire the recordings. The animals were acclimated in cages in a dimly lit, quiet room for 10 minutes. After the acclimation period, the first examination (T0) was performed. Ten minutes after the random administration of the protocols assigned to each group, a second examination (T10) was conducted for comparison. Both protocols evaluated in this study induced electrocardiographic changes, although with different intensities. It was concluded that in G1, dexmedetomidine induced the occurrence of arrhythmias, including second-degree atrioventricular block (Mobitz type II) and bradycardia associated with sinus arrest. In G2, acepromazine was associated with bradycardia accompanied by sinus arrest. However, the inclusion of methadone in both protocols makes it difficult to determine the true cause of bradycardia in these patients.