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      Continuous infusion in adult females dogs submitted to ovariohysterectomy with midazolam-xylazine and/or medetomidine pre-treated with methotrimeprazine and buprenorphine Translated title: Infusão continua em cães fêmeas submetidas à ovariohisterectomia com midazolam/cetamina/xilazina e/ou medetomidina pré-tratadas com levomepromazina e buprenorfina

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          PURPOSE: To compare, by continuous infusion of ketamine or medetomidine combined to methotrimeprazine and buprenorphine, ketamine and midazolam, the degree of hypnosis, myorelaxation, anesthetic quality and surgical feasibility through evaluation of possible parametric alterations and recovery quality. METHODS: 20 healthy adult females dogs, aged 3 to 5 years, body weight between 7 and 15 kg, were assigned randomly and homogenously to 2 groups of 10 animals each (n=10), group 1 (G1) and group 2 (G2), respectively. Animals of G1 were subjected to a pre-treatment with intravenous 1.0 mg/kg methotrimeprazine and or 3ì/kg. After 15 minutes, a 5.0 mg/kg ketamine and 0.2 mg/kg midazolam were intravenously injected. Immediately after induction, an anesthetic combination of 0.4 mg/kg/h midazolam, 20 mg/kg/h ketamine and 1.0 mg/kg/h xylazine, was continuously and intravenously administered for 30 minutes. The same techniques were used in G2 except for the substitution of xylazine for 30ìg/kg/h medetomidine. RESULTS: In G1 there was a 1st and 2nd degree atrioventricular heart block, a longer recovery period and lower quality. In G2 a 1st degree atrioventricular heart block occurred but isolated and ephemeral. CONCLUSIONS: The continuous infusion method, besides reducing drugs utilization, prevented collateral effects allowing a more tranquil recovery with no excitations, both protocols permitted the surgical procedure (ovary-hysterectomy) bringing about a reduction in hypnosis and an accentuated myorelaxation. Xylazine and medetomidine showed a similar pharmacodynamic behavior but with different clinical aspects. The electrocardiographic alterations observed in G2 and in a lower degree in G1 must be well studied. Describers: dogs, ketamine, methotrimeprazine, medetomidine, midazolam and xylazine.

          Translated abstract

          OBJETIVO: Comparar através de infusão contínua de xilazina ou medetomidina associada à metotrimeprazina e buprenorfina, cetamina e midazolam, o grau de hipnose, miorrelaxamento e qualidade anestésica e a viabilidade cirúrgica, avaliando eventuais alterações paramétricas e qualidade de recuperação. MÉTODOS: Foram utilizados 20 cães fêmeas, adultas, hígidas (3 a 5 anos de idade) com peso corporal entre 7 e 15 quilos, escolhidas e distribuídas aleatoriamente de forma homogênea em 2 grupos de 10 animais cada, (n=10) sendo estes designados por Grupo 1 (G1), e Grupo 2 (G 2). Em G1, os animais foram submetidos a um pré-tratamento com metotrimeprazina na dose de 1,0 mg/kg e buprenorfina na dose de 0,003mg/kg ou 3 µg/kg intravenoso. Decorridos 15 minutos, administrou-se cetamina na dose de 5,0 mg/kg e midazolam na dose de 0,2 mg/kg intravenoso. Imediatamente após a indução iniciou-se administração contínua, por um período de 30 minutos, da associação anestésica de midazolam 0,4 mg/kg/h, cetamina 20mg/kg/h e xilazina 1,0 mg/kg/h IV. Em G 2 utilizou-se a mesma técnica empregada em G1 substituindo-se, a xilazina pela medetomidina na dose de 30µg/kg/h. RESULTADOS: Verificou-se em G1 bloqueio átrio-ventricular de primeiro e segundo grau, período de recuperação mais longo além de menor qualidade. Em G 2 observou-se bloqueio átrio-ventricular de primeiro grau isolado e de ação fugaz. CONCLUSÕES: Ao se aplicar o método de infusão contínua, além da redução dos fármacos aplicados, evitaram-se efeitos colaterais permitindo uma recuperação mais tranqüila e isenta de excitações, ambos os protocolos permitiram a realização do ato cirúrgico (ovário-salpingo-histerectomia), causando uma redução da hipnose e um miorrelaxamento acentuado. A xilazina e a medetomidina apresentam um comportamento farmacodinâmico semelhante, porém com aspectos clínicos diferentes, as alterações eletrocardiográficas observadas em G 2 e em menor grau em G1 devem ser melhor estudadas.

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          Most cited references 66

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          A review of the physiological effects of alpha2-agonists related to the clinical use of medetomidine in small animal practice.

           M Sinclair (2003)
          Medetomidine is a relatively new sedative analgesic drug that is approved for use in dogs in Canada. It is the most potent alpha2-adrenoreceptor available for clinical use in veterinary medicine and stimulates receptors centrally to produce dose-dependent sedation and analgesia. Significant dose sparing properties occur when medetomidine is combined with other anesthetic agents correlating with the high affinity of this drug to the alpha2-adrenoreceptor. Hypoventilation occurs with medetomidine sedation in dogs; however, respiratory depression becomes most significant when given in combination with other sedative or injectable agents. The typical negative cardiovascular effects produced with other alpha2-agonists (bradycardia, bradyarrhythmias, a reduction in cardiac output, hypertension +/- hypotension) are also produced with medetomidine, warranting precautions when it is used and necessitating appropriate patient selection (young, middle-aged healthy animals). While hypotension may occur, sedative doses of medetomidine typically raise the blood pressure, due to the effect on peripheral alpha2-adrenoreceptors. Anticholinergic premedication has been recommended with alpha2-agonists to prevent bradyarrhythmias and, potentially, the reduction in cardiac output produced by these agents; however, current research does not demonstrate a clear improvement in cardiovascular function. Negatively, the anticholinergic induced increase in heart rate potentiates the alpha2-agonist mediated hypertension and may increase myocardial oxygen tension, demand, and workload. Overall, reversal with the specific antagonist atipamezole is recommended when significant cardiorespiratory complications occur. Other physiological effects of medetomidine sedation include; vomiting, increased urine volumes, changes to endocrine function and uterine activity, decreased intestinal motility, decreased intraocular pressure and potentially hypothermia, muscle twitching, and cyanosis. Decreased doses of medetomidine, compared with the recommended label dose, should be considered in combination with other sedatives to enhance sedation and analgesia and lower the duration and potential severity of the negative cardiovascular side effects. The literature was searched in Pubmed, Medline, Agricola, CAB direct, and Biological Sciences.
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            Análise de medidas repetidas em experimentos biológicos

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              Medetomidine sedation in dogs and cats: a review of its pharmacology, antagonism and dose.

              Medetomidine is a relatively new sedative analgesic in dogs and cats but some precautions are required when using it. It is a potent alpha 2-adrenoceptor agonist and stimulates receptors centrally to produce dose-dependent sedation and analgesia and receptors centrally and peripherally to cause marked bradycardia and decrease the cardiac output. While hypotension occurs frequently, higher doses of the sedative can raise the blood pressure due to an affect on peripheral receptors. Slowing of the respiratory rate is a frequent effect of medetomidine with some dogs showing signs of cyanosis. Other actions that follow medetomidine use are slowing of gastrointestinal motility, hypothermia, changes to endocrine function and, occasionally, vomiting and muscle twitching. The clinical use of medetomidine in dogs and cats is discussed. Recommended dose rates are presented along with precautions that should be taken when it is used alone for sedation, as an anaesthetic premedicant or in combination with ketamine, propofol or opioids. Hypoxaemia occurs frequently in dogs given medetomidine and propofol. The actions of medetomidine can be rapidly reversed with the specific alpha 2-adrenoceptor antagonist, atipamezole, which is an advantage because undesirable and sedative actions of medetomidine can be terminated.

                Author and article information

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                Acta Cirurgica Brasileira
                Acta Cir. Bras.
                Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia (São Paulo )
                August 2007
                : 22
                : 4
                : 272-278
                [1 ] Universidade Estadual Paulista Brazil
                [2 ] Universidade Estadual Paulista Brazil
                Product Information: website


                Methotrimeprazine, Medetomidine, Midazolam, Xylazine, Dogs, Metotrimeprazina, Medetomidina, Xilazina, Cães


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