Diferentes concentrações de óxido nitroso ou oxigênio, em suínos anestesiados com propofol e mantidos em ventilação controlada à pressão
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Data
2016-07-22
Autores
Carneiro, Rodrigo Lima [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Avaliaram-se os efeitos de diferentes concentrações do óxido nitroso (N2O) e da fração inspirada de oxigênio (FiO2) sobre a hematose, os parâmetros cardiorrespiratórios, intracranianos e o índice biespectral, em suínos anestesiados com propofol e mantidos em ventilação controlada a pressão. Para tanto, foram utilizados 48 suínos da raça Large White, machos ou fêmeas, distribuídos aleatoriamente em seis grupos: GN10(FiO2 = 0,9 e N2O = 0,1), GA10 (FiO2 = 0,9 e ar comprimido = 0,1), GN30(FiO2 = 0,7 e N2O = 0,3), GA30(FiO2 = 0,7 e ar comprimido = 0,3), GN50(FiO2 = 0,5 e N2O= 0,5), GA50 (FiO2 = 0,5 e ar comprimido = 0,5). Para todos os suínos, empregou-se como medicação pré- anestésica azaperona (2 mg/Kg) administrada pela via intramuscular. O propofol foi utilizado para indução e manutenção anestésicas (0,5 mg/Kg/min). Após a intubação orotraqueal, a sonda de Magill foi acoplada ao aparelho de anestesia inalatória equipado com ventilador volumétrico/pressométrico, para o fornecimento das misturas gasosas nas concentrações preconizadas para cada grupo. Após 100 minutos da indução anestésica foi administrado bolus, por via intravenosa, de rocurônio (0,6 mg/Kg) seguido por infusão contínua do mesmo fármaco (0,6 mg/Kg/h). Continuamente, iniciou-se a ventilação controlada ciclada a pressão (15 cmH2O) ajustada de maneira a permitir leitura de capnometria entre 35 e 45 mmHg. As observações das variáveis foram realizadas 100 minutos após a indução da anestesia (M0) e em intervalos de 15 minutos (de M15 a M75). Os dados foram submetidos à análise de variância de duas (Two-way ANOVA) e de uma via (One-way ANOVA), seguidas pelo teste de Bonferroni (p<0,05). Os resultados mostraram que houve alterações nas variáveis hemogasométricas (PaO2, PaCO2, SaO2, pHa, PvCO2 e SvO2), nos parâmetros da mecânica ventilatória (Vt, Vm, Tins, AaDO2, CvO2, Qs/Qt, P(a-ET)CO2, IR, IO, VO2, IVO2, TeO2), nas variáveis cardiovasculares (PAD, PAM, PVC, DC, PAPm, RVP e IRVP), nos parâmetros intracranianos (PPC e TIC) e no índice biespectral (BIS, QS e TS), sendo registradas diferenças significativas intergrupais. Em todos os grupos, as correlações entre Qs/Qt e AaDO2, Qs/Qt e IR, Qs/Qt e a/A e por fim, Qs/Qt e IO, foram fortes, excetuando-se GN10 nas correlações Qs/Qt e IR, Qs/Qt e IO que apresentaram-se moderadas. Concluiu-se que as diferentes FiO2 e concentrações de N2O não alteram as variáveis hemodinâmicas, cardiovasculres e intracranianas, porém o houve dimininuição do BIS quando utiliza-se N2O na concentração de 50%. FiO2 de 0,9 principalmente se associada ao N2O, deve ser evitada por contribuir com o aumento do shunt e a FiO2 de 0,7 sem adição de óxido nitroso na mistura gasosa mostrou-se mais adequada para ser utilizada durante a ventilação controlada à pressão em suínos anestesiados com propofol.
The effects of different concentrations of nitrous oxide (N2O) and fraction of inspired oxygen (FiO2) on hematosis, cardiorespiratory and intracranial parameters and bispectral index were evaluated in pigs anesthetized with propofol and maintained with pressure-controlled ventilation. Forty-eight Large White pigs, male or female, were randomly assigned into six groups:GN10 (FiO2 = 0.9 and N2O = 0.1), GA10 (FiO2 = 0.9 and compressed air = 0.1), GN30 (FiO2 = 0.7 and N2O = 0.3), GA30 (FiO2 = 0.7 and compressed air = 0.3), GN50 (FiO2 = 0.5 and N2O = 0.5) GA50 (FiO2 = 0.5 and compressed air = 0.5). Azaperone (2 mg/Kg) was used as standard pre-anesthetic medication and Propofol was used to induce and maintain anesthetic state (0.5 mg/Kg/min). Following endotracheal intubation, the Magill tube was coupled to an anesthesial equipped with a special fan which was able to control pressure/ volume of the gas mixture for each studied group. After 100 minutes of anesthetic induction, an intravenous bolus of rocuronium (0.6 mg/Kg) was administered, followed by continuous infusion of the same drug (0.6 mg/Kg/h). Then mechanical ventilation using cycled pressure (15 cmH2O) was adjusted in order to allow capnometry readings in between 35 and 45 mmHg. The observations of the variables were performed 100 minutes after anesthetic induction (M0) and at 15 minute intervals (M15 to M75). Data were subjected to two-way and one-way analysis of variance (ANOVA) followed by Bonferroni correction (p<0.05).The results showed changes in several variables and also significant intergroup differences were noticed. Among the main changes were: blood gas variables (PaO2, PaCO2, SaO2, pHa, PvCO2 and SvO2); mechanical ventilation parameters (Vt, Vm, Tins, AaDO2, CvO2, Qs/Qt, P (a-ET) CO2 , IR, IO, VO2, IVO2, TeO2); cardiovascular variables (DAP, MAP, PVC, DC, mPAP, PVR and PVRI); intracranial parameters (PPC and ICT) and also in the bispectral index (BIS, QS and TS). In all groups, the correlations between Qs/Qt and AaDO2, Qs/Qt and IR, Qs/Qt and a/A and finally, Qs/Qt and IO, were strong, except for GN10 (correlations Qs/Qt and IR, Qs/Qt and IO) that were moderate. It was concluded that the different FiO2 and N2O concentrations did not change hemodynamic variables , and intracranial cardiovasculres , but there was BIS decrease when N2O is used at a concentration of 50% . FiO2 0.9 mainly associated with N2O should be avoided for contributing to the increase of the shunt and FiO2 of 0.7 without the addition of nitrous oxide in the gas mixture was more suitable to be used during pressure controlled ventilation in pigs anesthetized with propofol.
The effects of different concentrations of nitrous oxide (N2O) and fraction of inspired oxygen (FiO2) on hematosis, cardiorespiratory and intracranial parameters and bispectral index were evaluated in pigs anesthetized with propofol and maintained with pressure-controlled ventilation. Forty-eight Large White pigs, male or female, were randomly assigned into six groups:GN10 (FiO2 = 0.9 and N2O = 0.1), GA10 (FiO2 = 0.9 and compressed air = 0.1), GN30 (FiO2 = 0.7 and N2O = 0.3), GA30 (FiO2 = 0.7 and compressed air = 0.3), GN50 (FiO2 = 0.5 and N2O = 0.5) GA50 (FiO2 = 0.5 and compressed air = 0.5). Azaperone (2 mg/Kg) was used as standard pre-anesthetic medication and Propofol was used to induce and maintain anesthetic state (0.5 mg/Kg/min). Following endotracheal intubation, the Magill tube was coupled to an anesthesial equipped with a special fan which was able to control pressure/ volume of the gas mixture for each studied group. After 100 minutes of anesthetic induction, an intravenous bolus of rocuronium (0.6 mg/Kg) was administered, followed by continuous infusion of the same drug (0.6 mg/Kg/h). Then mechanical ventilation using cycled pressure (15 cmH2O) was adjusted in order to allow capnometry readings in between 35 and 45 mmHg. The observations of the variables were performed 100 minutes after anesthetic induction (M0) and at 15 minute intervals (M15 to M75). Data were subjected to two-way and one-way analysis of variance (ANOVA) followed by Bonferroni correction (p<0.05).The results showed changes in several variables and also significant intergroup differences were noticed. Among the main changes were: blood gas variables (PaO2, PaCO2, SaO2, pHa, PvCO2 and SvO2); mechanical ventilation parameters (Vt, Vm, Tins, AaDO2, CvO2, Qs/Qt, P (a-ET) CO2 , IR, IO, VO2, IVO2, TeO2); cardiovascular variables (DAP, MAP, PVC, DC, mPAP, PVR and PVRI); intracranial parameters (PPC and ICT) and also in the bispectral index (BIS, QS and TS). In all groups, the correlations between Qs/Qt and AaDO2, Qs/Qt and IR, Qs/Qt and a/A and finally, Qs/Qt and IO, were strong, except for GN10 (correlations Qs/Qt and IR, Qs/Qt and IO) that were moderate. It was concluded that the different FiO2 and N2O concentrations did not change hemodynamic variables , and intracranial cardiovasculres , but there was BIS decrease when N2O is used at a concentration of 50% . FiO2 0.9 mainly associated with N2O should be avoided for contributing to the increase of the shunt and FiO2 of 0.7 without the addition of nitrous oxide in the gas mixture was more suitable to be used during pressure controlled ventilation in pigs anesthetized with propofol.
Descrição
Palavras-chave
Anestesia intravenosa, Atelectasia, Ventilação mecânica, Pressão positiva, Atelectasis, Intravenous anesthesia, Inhalational anesthetic, Mechanical ventilation, Positive pressure