Ademar Luiz Dallabrida

Neoformação óssea e osteointegração de biomateriais micro e nanoestruturados em ovinos

A substituicao de parte do tecido osseo se faz necessaria muitas vezes na rotina cirurgica, seja em funcao de fraturas, neoplasias osseas ou enfermidades ortopedicas que acarretem em perda ossea. Neste sentido, tem se buscado biomateriais capazes de promover esta substituicao, evitando o uso de enxertos ou transplantes osseos. O objetivo deste trabalho foi avaliar a capacidade osteoregenerativa de biomateriais em diferentes composicoes, em tibias de ovinos. Foram utilizadas oito ovelhas mesticas texel, com 12 meses de idade e peso medio de 28,5±7,4kg. Apos adequada preparacao anestesica e cirurgica, foram produzidos tres defeitos osseos na diafise das tibias em sua face medial, totalizando seis defeitos de 6mm cada, sendo que quatro foram preenchidos por biomateriais, e dois por fragmentos osseos retirados do proprio animal (autocontrole). Os materiais implantados foram: hidroxiapatita (HA), tricalcio fosfato-β (TCP-β), hidroxiapatita/tricalcio fosfato-b 60/40 (HA/TCP-b 60/40) e o nanocomposito hidroxiapatita/alumina a 5% (HA/Al2O3 a 5%). Os animais foram alocados em dois grupos: Grupo 60 (n=04), em que os animais foram eutanasiados apos 60 dias da colocacao dos implantes e Grupo 90 (n=04), em que a eutanasia ocorreu 90 dias apos a colocacao dos implantes. Foram realizadas radiografias nos periodos pre-operatorio, imediatamente apos o procedimento e aos 30, 60 e 90 dias de pos-operatorio, a fim de excluir qualquer alteracao previa ou complicacao pos-operatoria, capaz de comprometer o estudo. Apos a eutanasia, foram coletadas as tibias para avaliacao macro e microscopica, por meio de microscopia eletronica de varredura (MEV) e microscopia optica. Os resultados encontrados mostraram uma boa capacidade de neoformacao ossea e uma lenta absorcao da HA. O TCP-β foi rapidamente absorvido e apresentou boa capacidade osteoindutiva e osteocondutiva, sendo observada neoformacao ossea no interior dos grânulos deste biomaterial. O composto bifasico HA/TCP-β (60/40) apresentou o melhor resultado a longo prazo, devido ao melhor controle na solubilizacao e liberacao dos ions calcio e fosfatos para o meio biologico durante o processo de neoformacao ossea. O biomaterial nanocomposito HA/Al2O3 a 5% nao apresentou resultados promissores neste estudo, e sugerem-se novas pesquisas a fim de investigar melhor o potencial e aplicabilidade deste novo biomaterial. Conclui-se que a hidroxiapatita, o tricalcio fosfato-β e a associacao HA/TCP-β (60/40) apresentam excelente capacidade de reparacao ossea, podendo ser utilizados como substitutos osseos; a associacao HA/TCP-β (60/40) e o melhor dentre os biomateriais estudados, pois apresenta velocidade de absorcao intermediaria em relacao a HA e ao TCP-β isolados, fornecendo ainda uma sustentacao adequada ao tecido neoformado; o biomaterial HA/Al2O3 5% se mostrou incompativel, provocando reacao de rejeicao por parte do hospedeiro e com insignificante formacao de tecido osseo, sugerindo novas pesquisas acerca deste material.

Dexmedetomidina epidural em gatas submetidas à ovariosalpingohisterectomia sob anestesia total intravenosa com propofol e pré-medicadas com cetamina S(+) e midazolam

The objective of this study was to evaluate the effect of the epidural administration of dexmedetomidine in cats submitted to ovariohisterectomy, under continuous infusion of propofol. The cats received S(+) ketamine (5mg kg-1) and midazolan (0.5mg kg-1) as premedication by intramuscular injection, and propofol as induction agent (4mg kg-1), by intravenous injection. After that, the cats were intubated and kept on oxygen 100%. Subsequently the continuous infusion of propofol was initiated (0.3mg kg-1 min-1). The animals were divided into two groups, in the dexmedetomidine group (DEXG, n=6,2µg kg-1) dexmedetomidine was administered by epidural injection, and in the control group (SALG, n=6) saline solution was administered by the same way. In both groups the final volume was 0.26 mL kg-1 completed with NaCl 0.9%. Fentanyl administration was necessary at T10 in 33.3% of the patients. During the continuous infusion of propofol, the medial palpebral reflex was present in 66.6% of the animals of SALG and in 16.6% of the animals of DEXG. The eyeball was centralized in all the animals of SALG and 83.4% of the animals of DEXG the eyeball were with ventral rotation. Reduction of the heart rate was observed after anesthesia induction in both groups. The mean arterial pressure was significantly lesser at T0 and T5 in the DEXG and greater at T10 in the SALG when compared to the basal values. The respiratory rate was lesser in the DEXG at T20 and T30 when compared to SALG. The SaO2 and PaO2 were bigger from T5 to T40. The PaCO2 bigger values were observed at T5, T10, T20, T30 and T40 for the DEXG and at T5, T10 and T20 in the SALG when compared to the basal values. In the anesthetic recovery, 50% and 16.6% of the animals presented aggressiveness in the SALG and DEXG, respectively. To the wound pain threshold, it was observed that 33.3% of animals of SALG and 66.7% of the animals of DEXG received score 0 (without reaction). It was concluded that the animals that received dexmedetomidine administration by epidural injection, presented more stable anesthetic plan with greater analgesia degree in the peri and postoperative period, better quality anesthesia recovery, and without significant cardiovascular and hemogasometric changes.

Anestesia geral inalatória ou total intravenosa associada a anestesia subaracnóidea, em ovinos

The purpose of this study was to evaluate the efficacy and safety of sheep submitted to inhalation anesthesia with isoflurane or total intravenous anesthesia with propofol, both associated with subarachnoid anesthesia. Fourteen animals were pre-medicated with 0.3mg.kg-1 morphine IM, and 5 minutes later received 20mcg.kg-1 detomidine IV. Then they were allocated into two groups: GISO (n=7), which were induced with 0.5mg.kg-1 of diazepam and 5mg.kg-1 of ketamine IV, and anesthesia maintenance was performed by isoflurane diluted in 100% oxygen; or GPRO (n=7), where animals were induced with 4mg.kg-1 propofol IV and subsequent maintenance anesthesia with its own infusion of 0.3mg.kg.min-1. To perform the bilateral tibial osteotomy, all animals received 0.5mg.kg-1 0.75% ropivacaine combined with 0.1mg.kg-1 morphine by the intrathecal route. There was a 40% reduction in mean heart rate after the sedative protocol in both groups, resulting in a 23% average reduction until the end of the review. Mean arterial pressure showed transient elevation of around 16%, after induction of anesthesia in GISO, but reducing it to the end of the procedure, as well as in GPRO. The average EtISO was 0.57 V% and average infusion rate of propofol was 0.24mg.kg-1.min-1. The total time of surgery, anesthesia and extubation was 66± 9.8, 92±7.0 and 13.8±1.5 minutes in GISO and 56±2.4, 82.9±4.6 and 5.4±1.5 minutes in GPRO. The maintenance of anesthesia with propofol or isoflurane produced similar anesthesia with minimal cardiovascular and blood gas effects, which are well tolerated in healthy sheep.