RESUMO
The purpose of this study was to compare cardiovascular and respiratory effects of two volumes of bupivacaine 0.25% (0.2 mL kg-1-treatment BUP02-and 0.4 mL kg-1 -treatment BUP04) administered epidurally at the lumbosacral intervertebral space in dogs anesthetized with isoflurane. This experimental prospective randomized crossover design trial used six mixed breed adult dogs, four neutered males and two spayed females. Each dog was anesthetized on three different occasions: the first for isoflurane minimum alveolar concentration (MAC) measurement, and the following two assigned treatments (BUP02 or BUP04). On the two treatment days, anesthesia was induced and maintained with isoflurane at 1.3 MAC during the experiments. Cardiovascular and respiratory measurements were recorded before (T0) and 5, 15, 30, 60 and 90 minutes after the epidural administration of bupivacaine. Comparisons between and within groups were performed by a mixed-model ANOVA and Friedman's test when appropriate followed by Bonferroni post-hoc test or Dunnet's test to compare time points within each treatment with T0 (p < 0.05). Mean arterial pressure decreased significantly from 15 to 90 minutes after the administration of BUP02 and from 5 to 60 minutes in BUP04, with lower values in BUP04 than in BUP02 lasting up to 30 minutes after bupivacaine administration. No significant changes in cardiac output and systemic vascular resistance were observed in either treatment. Hypoventilation was only detected in BUP04. Hemoglobin concentration and arterial oxygen content decreased after both treatment of bupivacaine with no significant decrease in oxygen delivery. Two dogs in BUP04 developed Horner's syndrome. The epidural administration of 0.4 mL.kg-1 of bupivacaine to dogs in sternal recumbency anesthetized with isoflurane 1.3 MAC caused more cardiovascular and respiratory depression than 0.2 mL.kg-1.
Assuntos
Anestésicos Inalatórios/farmacologia , Anestésicos Locais/farmacologia , Bupivacaína/farmacologia , Sistema Cardiovascular/efeitos dos fármacos , Isoflurano/farmacologia , Respiração/efeitos dos fármacos , Anestesia Epidural , Animais , Pressão Sanguínea/efeitos dos fármacos , Cães , Feminino , Masculino , Testes de Função RespiratóriaRESUMO
This study aimed to compare the sedative effects of morphine, meperidine and fentanyl, in combination with acepromazine (ACP) and their effects on physiologic values in dogs. Six healthy beagle dogs were randomly assigned to four treatments with 7-day washout intervals. In three treatments, ACP (0.05mg kg-1) was administered and 20 minutes later, the dogs received administration of 0.5mg kg-1 of morphine (ACPMOR), 5mg kg-1 of meperidine (ACPMEP) or 5µg kg-1 of fentanyl (ACPFEN). In treatment ACP HD MOR, 0.1mg kg-1 of ACP was administered in combination with 0.5mg kg-1 of morphine. All drugs were administered intravenously. Sedation scores were evaluated by a numeric descriptive scale (NDS: 0-3) and a simple numeric scale (SNS: 0-10). All variables were evaluated for 120 minutes. The administration of ACP caused mild to moderate sedation. Sedation was improved in all treatments after opioid administration, but significant differences were detected only in ACPMOR and ACP HD MOR. More dogs presented intense sedation (NDS=3.0) after administration of morphine (3/6 and 4/6 dogs in ACPMOR and ACP HD MOR versus 1/6 in other treatments). Duration of sedation was longer in ACPMOR and ACP HD MOR. Mild to moderate decreases in blood pressure, respiratory rate and temperature were observed in all treatments but decreased HR was observed only in ACPMOR and ACP HD MOR. No significant differences were observed in the aforementioned variables when twice the dose of ACP was used (treatment ACP HD MOR). Under the conditions of this study, administration of morphine, in combination with ACP, results in greater and longer sedation than meperidine and fentanyl. Increasing the dose of ACP, in combination with morphine, does not improve the degree of sedation. All combinations used were considered to be safe for healthy dogs.
O presente estudo objetivou comparar o efeito sedativo da morfina, meperidina e fentanil associados à acepromazina (ACP) e seus efeitos sobre as variáveis fisiológicas de cães. Seis cães Beagle hígidos foram aleatoriamente submetidos a quatro tratamentos com intervalo de 7 dias. Em três tratamentos, foi administrada ACP (0,05mg kg-1) e, após 20 minutos, 0,5mg kg-1 de morfina (ACPMOR), 5mg kg-1 de meperidina (ACPMEP) ou 5µg kg-1 de fentanil (ACPFEN). No tratamento ACP DA MOR, a dose de 0,1mg kg-1 de ACP foi associada a 0,5mg kg-1 de morfina. Todos os fármacos foram administrados pela via IV. Escores de sedação foram avaliados pela escala numérica descritiva (END: 0-3) e escala numérica simples (ENS: 0-10). Todas as variáveis foram avaliadas durante 120 minutos. A administração da ACP causou sedação leve à moderada. A sedação foi intensificada em todos os tratamentos após a administração do opioide, mas diferença significativa foi observada somente em ACPMOR e ACP DA MOR. Um número maior de cães apresentou sedação intensa (END=3,0) após a administração da morfina (3/6 e 4/6 cães em ACPMOR e ACP DA MOR versus 1/6 nos demais tratamentos). A duração do efeito sedativo foi mais longa em ACPMOR e ACP DA MOR. Houve redução leve a moderada na pressão arterial, frequência respiratória e temperatura em todos os tratamentos e redução significativa da frequência cardíaca somente nos tratamentos ACPMOR e ACP DA MOR. Não houve diferenças significativas nas variáveis estudadas quando o dobro da dose de ACP foi utilizada (tratamento ACP DA MOR). Nas condições deste estudo, a administração da morfina, em associação à ACP, resulta em sedação de maior intensidade e duração do que a meperidina e o fentanil. O aumento na dose de ACP, em associação à morfina, não intensifica o grau de sedação. Todas as associações foram consideradas seguras para cães hígidos.