Avaliação da concentração expirada de isoflurano em infusão continua de remifentanil em cadelas submetidas a mastectomia

Abstract

The aims of this study were to evaluate the effects of two constant rate infusions of remifentanil on end tidal isoflurane (ETiso) in dogs undergoing mastectomy surgery. Eighteen bitches, 12+2 years of age, weighing 15+5 Kg were randomized into 3 groups (n=6/group) and underwent unilateral mastectomy due to mammary neoplasia. All animals received the premedications of morphine (0.5 mg Kg -1 ) and acepromazine (0.03 mg Kg -1 ) by intramuscular route (IM). Propofol dose-effect was used for induction of anesthesia. The animals were intubated and connected to a circle breathing system, and IPPV (intermittent positive pressure ventilation) was used to maintain normocapnia with an oxygen flow rate of 2 L/min and FiO 2 100%. Anesthesia was maintained with isoflurane and saline solution (control group [GCON], n=6) or intravenous infusion of remifentanil at a rate of 0.15 µg Kg -1 min -1 (REMI 0.15 n=6) or 0.3 µg Kg -1 min -1 (REMI 0.3 n=6). Cardiopulmonary variables and ETiso were monitored before and every 15 minutes after the start of surgery. The data were analyzed by ANOVA with multiple repetitions between moments and ANOVA followed by the Student Newman Keuls test (≤0.05) for comparisons between groups. Heart rate was lower at all moments in the REMI 0.15 and REMI 0.3 groups than in the GCON, and heart rate was not significantly different between the two remifentanil infusion groups. Additionally, the arterial blood pressure values (SAP, MAP and DAP) were not different between all groups. Baseline values (before surgery) of ETiso were not different between the 3 groups. After the start of surgery, ETiso ranged from 1.37±0.3 to 1.05±0.19 in the control group; in the REMI 0.15 and REMI 0.3 groups, ETiso was 36.5% and 65.7% lower than in the control group (M15). Remifentanil infusion reduced ETiso in a dose-dependent manner in animals undergoing radical mastectomy without causing significant cardiopulmonary alterations. Key words: Dogs, mastectomy, remifentanil, isoflurane ResumoOs objetivos deste estudo são a avaliação dos efeitos de duas taxas fixas de infusão continua de remifentanil na concentração expirada de isoflurano (ETiso) em cadelas submetidas à mastectomia. aleatoriamente em 3 grupos (n=6/grupo) e submetidos à mastectomia unilateral devido a neoplasia mamária. Todos os animais foram pré-medicados com morfina (0,5 mg Kg -1 ) e acepromazina (0,03 mg Kg -1 ), ambas por via intramuscular (IM). A indução da anestesia foi realizada com propofol (doseefeito). Os animais foram intubados e conectados a um sistema circular com reinalação de gases. Foi utilizada ventilação com pressão positiva intermitente para manutenção de normocapnia com fluxo de oxigênio de 2 L/min e FiO 2 de 100%. A anestesia foi mantida com isoflurano e solução salina (grupo controle [GCON], n=6) ou infusão intravenosa de remifentanil na taxa de 0,15 µg Kg -1 min -1 (REMI 0,15 n=6) ou 0,3 µg Kg -1 min -1 (REMI 0,3 n=6). As variáveis cardiovasculares e a ETiso foram monitoradas antes e a cada 15 minutos após o início da cirurgia. Os dado...