EFEITOS DA CLONIDINA E DA RILMENIDINA SOBRE OS SISTEMAS CARDIORRESPIRATÓRIO E GASTROINTESTINAL DE EQUINOS

Clonidina e rilmenidina são fármacos utilizados em medicina humana como agentes anti-hipertensivos de ação central devido às suas ações sobre os receptores alfa2-adrenérgicos e imidazolínicos I1 no SNC. Atualmente a clonidina é também utilizada como medicação pré-anestésica e em anestesias espinhais e a rilmenidina, apesar da menor seletividade pelo receptor alfa2-adrenérgico, também tem demonstrado potencial antinociceptivo em modelos experimentais de dor. Neste estudo, seis equinos foram submetidos a quatro tratamentos: grupo R1 (0,014 mg/kg de rilmenidina); grupo R2 (0,021 mg/ kg de rilmenidina); grupo Clo (0,002 mg/kg de clonidina) e um grupo controle. Foram avaliadas as frequências cardíaca e respiratória, a pressão arterial sistólica e motilidade intestinal em níveis basais e, em seguida, 60 e 120 minutos após a administração oral dos fármacos. A rilmenidina reduziu a frequência cardíaca nas duas doses testadas, o que não ocorreu com a clonidina; variações discretas na pressão arterial sistólica em todos os tratamentos e redução na frequência respiratória nos tratamentos com 0,021 mg/kg de rilmenidina e 0,002 mg/kg de clonidina também foram observadas. São ainda necessários maiores estudos com doses e vias de administração diferentes para se elucidar maiores efeitos destes fármacos na espécie equina. Palavras-chave: agonistas alfa2-adrenérgicos; farmacologia; imidazolinas; motilidade intestinal; pressão arterial

ESTUDO INVESTIGATIVO DOS EFEITOS SEDATIVO E ANTINOCICEPTIVO DA CLONIDINA E DA RILMENIDINA EM EQUINOS

Clonidina e rilmenidina são fármacos que possuem diversos efeitos sistêmicos em função de suas ações sobre os receptores alfa-adrenérgicos e imidazolínicos, tais como hipotensão, bradicardia, redução do débito cardíaco e da resistência vascular periférica e sedação e antinocicepção dose-dependentes. O presente estudo teve como objetivo investigar e comparar os efeitos farmacológicos da clonidina e da rilmenidina sobre o limiar nociceptivo e a sedação de equinos. Foram utilizados 6 equinos adultos, machos e fêmeas, os quais foram submetidos a três tratamentos: (1) controle; (2) clonidina 0,002 mg/kg; e (3) rilmenidina 0,021 mg/kg. Os fármacos foram administrados por via oral e os animais foram avaliados em três momentos, sendo o primeiro (T0) imediatamente antes da administração dos medicamentos, após 60 minutos (T60) e após 120 minutos (T120). Foram investigados os efeitos sedativo e antinociceptivo através dos modelos de abaixamento de cabeça e da latência para o reflexo de retirada do membro, respectivamente. Nossos ensaios apontaram abaixamento de cabeça com significância estatística no tratamento com clonidina, indicando um efeito sedativo, o que não ocorreu com a administração de rilmenidina, e ambos os fármacos não foram capazes de aumentar o limiar nociceptivo. Concluímos que a clonidina por via oral é capaz de induzir leve sedação na dose testada neste estudo e que as doses utilizadas tanto para clonidina quanto para a rilmenidina não produzem antinocicepção em equinos

New Technique for Intrathoracic Implantation of Extraluminal Spiral Prostheses in the Trachea

Background: Extraluminal surgical procedures for intrathoracic tracheal collapse in dogs are not routinely performed. The patients are normally treated with different drugs or by intraluminal stents. However, in more severe cases, drug treatment does not always have good outcomes, and intraluminal prostheses can be correlated to several postoperative problems. In order to obtain better results, we aimed to develop a surgical technique for implantation of a new extraluminal helical prosthesis in the thoracic segment of the trachea through cervical access, associated with pneumatic mediastinoscopy for certification of the technique and minimization of possible complications.Materials, Methods & Results: Seven canine corpses (CCs) from non-traumatic death, weighing between 2 and 7 kg, were used. A ventral cervical approach to the trachea was associated with blunt mediastinal dissection. Trans cervical pneumatic mediastinoscopy was used for evaluation of the dissection and location of the implant. These were compared with the necropsy findings by the exact Wilcoxon two-sample test, with P < 0.05. The results of necropsy and mediastinoscopy did not present significant differences at P < 0.05. During the examinations, the presence of some mediastinal visceral lesions caused by the prosthesis, the integrity of the mediastinum and possible lesions to RLN and blood vessels (BV) were analyzed. We also investigated the location of the distal part of the prosthesis in the thoracic segment of the trachea and its dissection. To evaluate the technique, statistical comparison was made between mediastinoscopy and necropsy findings. The data were compared by the Wilcoxon test at 5% probability. The tracheas of all CCs were efficiently dissected, but in some cases problems that can happen during the procedure were noticed. This was checked by mediastinoscopy and confirmed by necropsy. The median of the scores was 1 (good dissection and visualization), with variance of zero for mediastinoscopy and 0.14 for necropsy. In the mediastinoscopy of one CC, the prosthesis crossed the tracheal bifurcation, involving the posterior vessels of this region, which was confirmed by necropsy. However, the dissection showed no vascular lesions. The integrity of the mediastinum was assessed only by mediastinoscopy. There was no impairment caused by any of the procedures performed. This resulted in a median score of 1 (integrity) with zero variance. When the positioning of the prosthesis was evaluated in relation to the tracheal bifurcation, identical values were obtained by both methods. The median score was 1, with variance of 0.62. No statistical differences were found between the two evaluation methods for the analyzed variables. This demonstrates the strong potential of the proposed evaluation techniques.Discussion: Our results show that the execution of the technique is possible, but some complications may occur. Mediastinoscopy as an evaluation procedure can pose some complications, these considerations are important, but by using technique proposed in this study, these factors are minimized due to the ease of technical implantation of the extraluminal tracheal stent, without the need for several instruments competing in the inflated mediastinal space. We concluded that the technique is viable and a safe method with minimal invasion for investigation and treatment of mediastinal diseases, presenting low impairment of the paratracheal structures, and that mediastinoscopy can be used as a transoperative evaluation method to minimize complications

EFFECTS OF CLONIDINE AND RILMENIDINE ON CARDIORESPIRATORY AND GASTROINTESTINAL SYSTEMS OF HORSES

Clonidine and rilmenidine are drugs used in human medicine as central acting antihypertensive agents due to their actions on the alpha2-adrenoceptor and I1 imidazoline receptors in the central nervous system. Currently, clonidine is also used as a pre-anesthetic medication and in spinal anesthesia, and rilmenidine, despite the lower selectivity for alpha2-adrenergic receptors than clonidine, has also shown antinociceptive potential in experimental pain models. In this study, six horses were submitted to four treatments: R1 group (0.014 mg/kg of rilmenidine); R2 group (0.021 mg/kg of rilmenidine); Clo group (0.002 mg/kg of clonidine), and a control group. The assessment comprehended their heart and respiratory rates, systolic blood pressure and intestinal motility at basal levels and, then, 60 and 120 minutes after the oral administration of the drugs. Rilmenidine decreased heart rate on   the two tested doses, which did not occur in the clonidine treatment; slight variations in systolic blood pressure in all treatments and respiratory rate reduction in treatments with rilmenidine at 0.021 mg/ kg and clonidine at 0.002 mg/kg were also observed. Further studies with different dosages and varied administration routes are still necessary in order to elucidate more effects of these drugs on horses. Keywords:    alfa2-adrenoceptor agonists; blood pressure; imidazolines; intestinal motility; pharmacology