Bispectral index assessment in calves subjected to the continuous infusion of propofol combined with fentanyl administration

portuguesO estudo teve por objetivo avaliar o indice biespectral (BIS) durante a infusao continua de propofol associado ou nao ao fentanil em bezerros. Foram utilizados oito animais machos entre seis e doze meses de idade, holandeses, com massa corporal media de 123±18kg. Todos os animais participaram de ambos os grupos, respeitando-se sempre um intervalo minimo de uma semana entre uma anestesia e outra, sendo aleatoriamente distribuidos entre os grupos. A anestesia nos bezerros foi induzida com propofol na dose de 5mg kg-1; intravenoso (IV), grupo controle (GP) ou propofol 4mg kg-1 associado ao fentanil 0,001mg kg-1; IV, grupo fentanil (GF) e posicionados em decubito lateral direito, onde permaneceram respirando espontaneamente ar ambiente. Ato continuo, a manutencao anestesica foi realizada pela infusao continua de propofol na taxa de 0,6mg kg-1 min-1; IV GP, associado ou nao a infusao de fentanil 0.001mg kg-1 hora-1 GF. A mensuracao das variaveis do BIS, indice de qualidade de sinal (IQS) eletromiografia (EMG), frequencia cardiaca (FC), frequencia respiratoria (f) e dioxido de carbono ao final da expiracao (ETCO2) foram avaliadas antes da inducao anestesica no momento basal (MB), e 15, 30, 45 e 60 minutos apos o inicio da infusao continua dos farmacos (M15, M30, M45 e M60, respectivamente); o tempo de recuperacao tambem foi avaliado. Nao foram observadas diferencas significativas entre os grupos nas variaveis do BIS e o tempo de recuperacao foi maior no GF. A co-administracao das infusoes de propofol e fentanil, nas doses utilizadas nesse estudo, nao alterou os valores do BIS em bezerros, porem, prolongou o tempo de recuperacao. Palavras-chave: bezerros; ruminantes; anestesia balanceada; monitoracao anestesica EnglishThe aim of this study was to evaluate the bispectral index (BIS) effects in calves through continuous infusion of propofol with or without fentanyl. Eight Holstein male calves (ages from six to twelve months old) with an average weight of 123±18kg were used. All animals participated in both groups, always keeping a minimum interval of one week between the anesthetic procedures; the calves were randomly distributed between groups. Anesthesia was induced with an intravenous (IV) dose of propofol of 5mg kg-1 in control group (GP) or with propofol (4mg kg-1) associated with IV fentanyl 0.001mg kg-1(GF). All the calves were positioned in right lateral recumbency and were allowed to spontaneously breathe room air. Subsequently, the anesthesia was maintained by continuous infusion of propofol at the rate of 0.6mg kg-1 min-1 IV in GP, and associated with the infusion of fentanyl 0.001mg kg-1 hour-1 in GF. Measurements of BIS, signal quality index (SQI) and electromyography (EMG) were evaluated before anesthesia induction (TB), and at 15, 30, 45 and 60 minutes after the beginning of continuous drugs infusion (T15, T30, T45 and T60, respectively). The heart rate (HR), respiratory rate (f), end-tidal carbon dioxide tension (ETCO2) and recovery times were evaluated as well. No significant differences were observed between the groups in the BIS variables and the recovery time was longer in GF. Co-administration of propofol and fentanyl infusions, at the doses reported here, did not change the values of BIS in cattle, but delayed the recovery time. Key words: calves; ruminants; balanced anesthesia; anesthetic monitoring