Dexmedetomidina associada a nalbufina, butorfanol ou metadona: comparação da sedação, influência sobre a dose de indução anestésica do propofol e na reação a cateterização venosa com ou sem o uso do creme EMLA em gatos

Abstract

The present study was developed at the feline medicine service of the Universidade Federal Rural do Rio de Janeiro Veterinary teaching hospital. Forty-two female cats recruited for spaying were enrolled in the study. All animals were classified by the American Society of Anesthesiologists (ASA) risk classification as ASA I or II to be included in the study. The main goal of the study was to evaluate the sedation and the effects over the propofol dose needed to induce anesthesia in cats premedicated with dexmedetomidine (0,01 mg.kg-1) associated with nalbuphine (DN; 0,3 mg.kg-1), butorphanol (DB; 0,3 mg.kg-1) or methadone (DM; 0,3 mg.kg-1). The secondary goal was to evaluate the efficacy of lidocaine-prilocaine cream (EMLA cream) in reducing the response to venous catheterization in cats of groups DN and DM by applying the cream for 20 minutes in 6 cats in each group and not applying in other 6 cats to create a negative control. Cats were randomly allocated in of the three premedication groups and after acclimation received in the quadriceps muscles one of the protocols. Sedation scores were recorded 10, 20 and 30 minutes after premedication. Six cats in each of DN and DM groups had applied on the antebrachium EMLA cream 10 minutes after premedication. After sedation scores 30 minutes after premedication cats had a catheter placed on the left cephalic vein and the animals enrolled to score reaction to catheter placement had it done. Anesthetic induction with propofol (5 mg.kg.min-1) was then performed and the amount of propofol needed to induce anesthesia recorded. Sedation scores did not differ among groups but an increment in sedation was observed along time in all three groups with intense sedation 30 minutes after premedication. In the same fashion the time for lateral recumbency did not differ among groups. Propofol dose to induce anesthesia also did not differ among premedication groups. The main side effect was emesis, present in 0/14 cats on DN, 2/14 cats in DB and 2/14 cats in DM. The reaction to catheter placement was lower in treated cats when compared to control cats. The synergistic or at least additive action between α-2 adrenoceptor agonists and opioids must be considered as one of the main factors leading to the high levels of sedation with short onset. We conclude that sedation with nalbuphine, butorphanol or methadone, associated with dexmedetomidine, at the present doses, produce intense sedation with shot onset, low incidence of emesis and may reduce the amount of propofol needed to induce anesthesia. Additionally, the combination of nalbuphine or methadone with dexmedetomidine, at the present doses, when associated with EMLA cream may abolish the reaction to intravenous catheter placement in cats.