Avaliação cardiorrespiratória em cadelas (Canis familiares) submetidas à infusão contínua com a associação de fentanil, cetamina e lidocaína com e sem adição de metadona sob anestesia com isofluorano

Abstract

The search for analgesia techniques in operative periods motivated researchers to develop analgesia protocols for each of the stages of anesthesia. In the trans-anesthetic, the most used techniques are the continuous infusion with associassion of analgesic (opioid), a local anesthetic and a dissociative anesthetic. Although these techniques guarantee proper analgesia for the period, they require greater power to the immediate postoperative period, since by the pharmacology of drugs used, this property would be difficult to achieve. So, alternatively, nonsteroidal anti-inflammatory drugs started to be used, however due to the high incidence of side effects it becomes an impractical alternative sometimes. Thus, the search for long term analgesic alternative with minimal occurrence of unwanted effects is the motivation of this study, the main object was the use of methadone as an alternative since it is an opioid with prolonged latency and duration, but not used much in daily anesthetic practice because of insufficient studies to ensure its safety when it is used intravenously and associated with other analgesics and anesthetic agents. This study aimed to evaluate the cardiorespiratory changes caused by adding methadone to continuous infusion with lidocaine, ketamine and fentanyl in dogs undergoing ovariohysterectomy under anesthesia with isoflurane. For this, 20 dogs were used and rendomly divided into two groups. The G1 had 10 bitches being subjected to continuous infusion of ketamine (10mg / kg / min), lidocaine (50ug / kg / min), fentanyl (0.03 ug / kg / min) and methadone (0.02mg / kg / min) and G2 received the same without the infusion methadone, and throughout the following all animals had their physiological parameters monitored. Regarding heart rate, systolic arterial pressure, diastolic arterial pressure, mean anrterial pressure, respiratory rate, body temperature, peripheral capillary oxygen saturation and electrocardiographic tracings were no significant differences between groups and times. Therefore it can be concluded that the addition of methadone to continuous infusion with lidocaine, ketamine and fentanyl in dogs undergoing ovariohysterectomy under anesthesia with isoflurane caused no significant cardiorespiratory changes. Thus, it is possible to conclude that the addition of methadone to continuous infusion with lidocaine, ketamine and fentanyl in dogs undergoing ovariosalpingohisterectomy under isoflurane anesthesia did not cause cardiorespiratory changes and provided an analgesic increase in the immediate postoperative period.