REMIFENTANIL INTRAOPERATIVE ANALGESIA. A COMPARATIVE STUDY WITH FENTANYL IN DOGS

1. REMIFENTANIL INTRAOPERATIVE ANALGESIA. A COMPARATIVE STUDY WITH FENTANYL IN DOGS Rubio M, Redondo JI, Carrillo JMª, Sopena JJ, Soler G* Facultad de Ciencias Experimentales y de la Salud.Universidad Cardenal Herrera -CEU.Valencia * Hospital Veterinario Marina Alta. Denia.Alicante OBJECTIVES The aim of this study was to evaluate the intraoperative analgesia of remifentanil in dogs, comparing with fentanyl and a placebo solution as well as the study of the haemodynamic and respiratory responses, and the patient recovery after two hours of anesthesia. MATERIAL Y METODO • Anesthetic protocol • Seven beagles dogs ASA I were anesthetized three times. All of them were anesthetized with the following anesthetic protocol: medetomidine (10 g/kg IV), propofol (3 mg/kg IV), sevoflurane and atracurium (150 g/kg IV), every 30 minutes. At the end of the procedure we reverted the effects of atracurium with a combination of atropine (0.01 mg/kg) and neostigmine (5 g/kg) intravenous. • 2. Analgesic protocol • Three different analgesic protocols were used and they were classified in these groups: • RMF: (remifentanil: 0,5 g/kg IV induction doses + 0,25 g/kg/min maintenance doses). • FEN: (fentanyl: 2 g/kg IV induction doses + 0,1 g/kg/min IV maintenance doses). • PCB (glucosade fluid infussion). • 3. Postanesthetic protocol • The following postanesthetic analgesic protocol was used in all groups: • morphine (0,2 mg/kg IM) and meloxicam (0,2 mg/kg IV) 20 minutes before the end of the procedure • 4. Painful evaluation • During the procedure, several cardiovascular and respiratory variables were studied every 5 minutes. Pain response was evaluated pinching with a forceps in the back paws for 1 minute. It was found that the animals were painful when the arterial pressure and heart rate increased by 10% in relation to the last measure. Times and quality of the recuperation were also evaluated comparing all groups. RESULTADOS The results of the study showed that the RMF and FEN groups presented a significantly lower EtSev than PCB group, with a decrease of 28.57% and 29,73% respectively. RMF showed the highest values in arterial pressures and PVC and intermediate values in heart rate and compliance. In this group, EtCO2 was lower than in the others. The lowest values in heart rate and arterial pressures were found in FEN group, while the highest heart rate and intermediate values in arterial pressures were observed in PCB`s group. The only value that was similar in the three groups was SpO2, because of the animals were inhalating 100% O2. The recuperation period was good and peaceful in all the animals, but recovery times were significantly lower in RMF dogs. CONCLUSIONES Tanto el remifentanilo (Ultiva), como el fentanilo (Fentanest), son dos fármacos útiles para proporcionar analgesia intraoperatoria en el perro. Tanto el remifentanilo (Ultiva) como el fentanilo (Fentanest) producen un descenso significativo del 28,57% y 29,73% respectivamente de la concentración mínima de sevoflurano necesario para mantener un plano anestésico adecuado que aboliera la respuesta del paciente a los estímulos dolorosos.  El remifentanilo (Ultiva) administrado en perfusión continua proporciona una mayor estabilidad hemodinámica y cardiovascular que el fentanilo (Fentanest) administrado de la misma forma.  Tras una anestesia de 120 minutos, la recuperación postoperatoria es suave, tranquila y sin complicaciones en el 100% animales, mostrando el Grupo RMF tiempos de recuperación significativamente inferiores a los grupos FEN y PCB. El protocolo de meloxicam (Metacam)- morfina (cloruro mórfico) a las dosis descritas proporciona una buena cobertura analgésica en el tratamiento del dolor postoperatorio.  Dada la depresión respiratoria producida tanto por el remifentanilo (Ultiva), como por el fentanilo (Fentanest) es muy recomendable emplear ventilación mecánica para asegurar la correcta oxigenación y la normocapnia en los pacientes.