À Profa. Dra. Sílvia Renata Gaido Cortopassi, pela confiança, apoio, dedicação, amizade e orientação durante este período de convivência. À Profa. Dra. Denise Tabacchi Fantoni, pelas oportunidades e ensinamentos fundamentais para a realização deste projeto. Ao Prof. Dr. Fábio Futema, pelo incentivo profissional e amizade que fez despertar o meu interesse pela anestesiologia. À Profa. Dra. Márcia Marques Jericó, pela liberação e apoio para realização do mestrado. Ao Prof. Cláudio Alves de Moura,

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... pelo conselhos e oportunidades oferecidas em ótimos anos de convivência e amizade. Ao Prof. Márcio Moreira pelo apoio na realização dos exames laboratoriais, além das palavras de incentivo e amizade. Às amigas e companheiras de profissão, Christianni Padovani D' Biaggi e Tatiana Regina Intelisano, pela colaboração na realização deste projeto. Aos enfermeiros Jesus, Otávio, Miron e Priscila, Juliana e Alex indispensáveis na realização deste trabalho. Ao técnico de laboratório Kazuo Kagihara, por estar sempre pronto a colaborar. À Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, por ter me aceitado nesta casa. À Universidade Anhembi Morumbi, por disponibilizar sua estrutura e profissionais para realização deste projeto. À Fundação de Amparo à Pesquisa do Estado de São Paulo -FAPESP, pelo apoio financeiro. ABSTRACT SOUZA, S. S. Effects of dexmedetomidine by epidural or continuous intravenous infusion in cats undergoing propofol-isoflurane anesthesia to ovariohysterectomy. [Efeitos da dexmedetomidina, por via epidural ou infusão contínua intravenosa, em gatas anestesiadas com propofol e isofluorano e submetidas a ovariossalpingohisterectomia]. 2006. 140 f. Dissertação (Mestrado em Medicina Veterinária) -Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, 2006. This study compared the effects of epidural or continuous intravenous infusion of dexmedetomidine in isoflurane-anesthetized cats undergoing ovariohysterectomy. Twenty-one cats (weight: 3.06±0.35 kg) were premedicated with dexmedetomidine (4 mcg.kg -1 , IM). Fifteen minutes later, propofol was titrated to allow endotracheal intubation and anesthesia was maintained in spontaneously breathing cats with isoflurane in oxygen using a Mapleson D system. Cats were randomly allocated to receive either epidural lidocaine (1 mg.kg -1 , G1, n=7) or epidural lidocaine (1 mg.kg -1 ) + dexmedetomidine (4 mcg.kg -1 , G2, n=7) or epidural lidocaine (1 mg.kg -1 ) + continuous intravenous infusion of dexmedetomidine (0,25 mcg.kg -1 . min -1 , G3, n=7). The volume of either epidural injection was adjusted to 0.3 mL.kg -1 with saline. The individual controlling depth of anesthesia was blinded to the drug being administered epidurally and intravenouslly. Heart (HR) and respiratory (RR) rates, systolic arterial blood pressure (SAP) and rectal temperature (RT) were recorded before and after 15 minutes of premedication. During anesthesia, heart (HR) and respiratory (RR) rates, invasive arterial blood pressures, end-tidal CO 2 , end-tidal isoflurane (ISOe), RT and muscular relaxation were recorded at 15 minute intervals from 20 until 80 minutes. Arterial blood gases were measured at 20 and 80 min after induction. HR, RR, RT, analgesia score, and recovery quality and times were compared for 3 hours after end of anesthesia. Paired t test were performed to compare the premedication effects and arterial blood gases at differents intervals. ANOVA with Tukey post-test and Friedmann with Dunn post-test were performed to parametric and nonparametric values, respectively (P<0.05). Dexmedetomidine premedication decreased HR, RR, SAP and RT. The induction dose of propofol was 7.4±1.4 mg.kg -1 . When compared to the G1, epidural dexmedetomidine significantly decreased HR from 20 to 65 minutes of anesthesia and 150 and 180 minutes after end of anesthesia, however, continuous intravenous infusion decreased HR all times during anesthesia and recovery time. When compared to G2, continuous intravenous infusion of dexmedetomidine decreased HR at 60 and 90 minutes during recovery. In the G1 mean±SD ISOe concentrations ranged form 0.86±0.28% to 1.91±0.63% from 20 to 80 min. At the same time interval, ISOe concentrations were significantly lower in the G2 (ISOe ranged from 0.70±0.12% to 0.97±0.20%) and G3 (ISOe ranged from 0.69±0.12% to 1.17±0.25%). PaCO 2 was significantly greater in G3 than G1 at 20 minutes. The recovery times were significantly lower in the G1 except for extubation time when compared with G2. There were no significant differences among groups for the remaining variables. It was concluded that premedication with dexmedetomidine produced cardiorespiratory depression. Epidural administration and continuous intravenous infusion of dexmedetomidine significantly reduced inhalant requirements for maintaining anesthesia and produced a better anesthesia recovery although of longer duration. Dexmedetomidine administration may cause bradycardia, however reduced HR does not affect arterial blood pressure. Key words: Dexmedetomidine. Continuous infusion. Epidural. Cats. KOROGLU, A.; DEMIRBILEK, S.; TEKSAN, H.; SAGIR, O.; BUT, A. K.; ERSOY, M. O. Sedative, haemodynamic and respiratory effects of dexmedetomidine in children undergoing magnetic resonance imaging examination: preliminary results. British Journal of Anaesthesia, v. 94, n. 6, p. 821-824, 2005. KUUSELA, E.; RAEKALLIO, M.; ANTTILA, M.; FALCK, I.; MÖLSÄ, S.; VAINIO, O. Clinical effects and pharmacokinetics of medetomidine and its enantiomers in dogs. Journal of Veterinary Pharmacology and Therapeutics, v. 23, n. 1, p. 15-20, 2000. KUUSELA, E.; RAEKALLIO, M.; VÄISÄNEN, M.; MYKKÄNEN, K.; ROPPONEN, H.; VAINIO, O. Comparison of medetomidine and dexmedetomidine as premedicants in dogs undergoing propofol-isoflurane anesthesia. VAINIO, O.; KAISTINEN, A.; KOBYLIN, S.; RAEKALLIO, M. Sedative, analgesic, and cardiovascular effects of levomedetomidine alone and in combination with dexmedetomidine in dogs. DE LANGE, S. Effects of a single pre-operative dexmedetomidine dose on isofluorane requirements and peri-operative haemodynamic stability. Anaesthesia, v. 52, n. 8, p. 736-744, 1997.