The coasting time affects the quality of cumulus-oocyte complexes in superstimulated ewes.

We hypothesized that the coasting time may be beneficial to the quality of cumulus-oocyte complexes recovered from live ewes, as reported in cattle. The present study assessed the effect of coasting times on the quantity and quality of cumulus-oocyte complexes (COCs) in sheep. All ewes were subjected to the "Day 0 protocol", followed by an ovarian stimulation (80 mg of pFSH in three decreasing doses), varying only the coasting time [12 (G12), 36 (G36), or 60 h (G60]. In Experiment 1, data regarding follicular population was assessed. In Experiment 2, the COC quality was checked by their morphology, brilliant cresyl blue (BCB) test, evaluation of chromatin condensation pattern, and oocyte diameter. In Experiment 3, genes related to oocyte developmental competence were evaluated in BCB + COCs. The oocytes in the G60 group had more (P < 0.05) large follicles than the other groups and oocytes with a greater diameter than the G12. Oocyte morphology was similar (P > 0.05) among groups, as well as the BCB + COCs quantity. The G60-oocytes presented a better (P < 0.05) configuration of chromatin condensation compared with the other groups and a greater (P < 0.05) gene expression of BMP15, MATER, ZAR1, and PTGS2 compared with G12, and PTGS2 and HAS2 compared with G36 group. In conclusion, 60 h of coasting time positively affects the quality of COCs recovered after subjecting ewes to the "Day 0 protocol" and ovarian superstimulation. Implementing the appropriate coasting time to a given protocol can positively impact the in vitro embryo production outcomes in sheep.

Cardiovascular and respiratory effects of lumbosacral epidural bupivacaine in isoflurane-anesthetized dogs: The effects of two volumes of 0.25% solution.

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.

Dose-finding study comparing three treatments of remifentanil in cats anesthetized with isoflurane undergoing ovariohysterectomy.

Objectives Three infusion rates of remifentanil were used in isoflurane-anesthetized cats undergoing ovariohysterectomy. The aim of this study was to identify a dosage regimen that would provide optimal anesthetic and surgical conditions, as well as to compare cardiovascular response to surgical stimulation, postoperative analgesia, anesthetic duration and quality of recovery among the tested remifentanil infusion rates. Methods Twenty-seven client-owned, mixed-breed adult healthy female cats were randomized to receive remifentanil 0.1 µg/kg/min (REMI01), remifentanil 0.2 µg/kg/min (REMI02) or remifentanil 0.4 µg/kg/min (REMI04). After premedication with acepromazine and induction of anesthesia with propofol, cats were mechanically ventilated and anesthesia was maintained at approximately 1.0 minimum alveolar concentration (MAC) of isoflurane (1.63% end-tidal isoflurane [ETISO]). Remifentanil infusion rate was increased or decreased by 20% if blood pressure had increased or decreased by 20% from previous values. Pulse rate (PR), systolic arterial pressure (SAP), esophageal temperature, pulse oximetry, end-tidal partial pressure of CO2 and ETISO were recorded at different time points during surgery. Meloxicam was administered before the end of surgery. Data within each treatment group were analyzed using a mixed-model ANOVA and Friedman's test followed by the Wilcoxon signed rank test. Bonferroni or Dunnett's post-hoc tests were used. The Kruskal-Wallis test followed by Dunn's post-hoc test were used to compare data between groups; significance was set at P <0.05. Results Time to sternal recumbency and time to standing were significantly longer in REMI04 than in the other groups. SAP was higher when compared with baseline in REMI01 and REMI02 groups than in REMI04. No significant difference in PR among groups was observed. One cat in REMI01 and another in REMI02 required postoperative rescue analgesia. Conclusion and relevance The dosage regimen of 0.4 µg/kg/min seemed to be the most appropriate to be used in cats undergoing ovariohysterectomy and anesthetized with 1.0 MAC of isoflurane.

Effect of tamoxifen on fibrosis, collagen content and transforming growth factor-ß1, -ß2 and -ß3 expression in common bile duct anastomosis of pigs.

End-to-end anastomosis in the treatment for bile duct injury during laparoscopic cholecystectomy has been associated with stricture formation. The aim of this study was to experimentally investigate the effect of oral tamoxifen (tmx) treatment on fibrosis, collagen content and transforming growth factor-ß1, -ß2 and -ß3 expression in common bile duct anastomosis of pigs. Twenty-six pigs were divided into three groups [sham (n = 8), control (n = 9) and tmx (n = 9)]. The common bile ducts were transected and anastomosed in the control and tmx groups. Tmx (40 mg/day) was administered orally to the tmx group, and the animals were euthanized after 60 days. Fibrosis was analysed by Masson's trichrome staining. Picrosirius red was used to quantify the total collagen content and collagen type I/III ratio. mRNA expression of transforming growth factor (TGF)-ß1, -ß2 and -ß3 was quantified using real-time polymerase chain reaction (qRT-PCR). The control and study groups exhibited higher fibrosis than the sham group, and the study group showed lower fibrosis than the control group (P = 0.011). The control and tmx groups had higher total collagen content than the sham group (P = 0.003). The collagen type I/III ratio was higher in the control group than in the sham and tmx groups (P = 0.015). There were no significant differences in the mRNA expression of TGF-ß1, -ß2 and -ß3 among the groups (P > 0.05). Tmx decreased fibrosis and prevented the change in collagen type I/III ratio caused by the procedure.

SHEEP AS AN EXPERIMENTAL MODEL FOR BIOMATERIAL IMPLANT EVALUATION

ABSTRACT Objective: Based on a literature review and on our own experience, this study proposes sheep as an experimental model to evaluate the bioactive capacity of bone substitute biomaterials, dental implant systems and orthopedics devices. The literature review covered relevant databases available on the Internet from 1990 until to date, and was supplemented by our own experience. Methods: For its resemblance in size and weight to humans, sheep are quite suitable for use as an experimental model. However, information about their utility as an experimental model is limited. The different stages involving sheep experiments were discussed, including the care during breeding and maintenance of the animals obtaining specimens for laboratory processing, and highlighting the unnecessary euthanasia of animals at the end of study, in accordance to the guidelines of the 3Rs Program. Results: All experiments have been completed without any complications regarding the animals and allowed us to evaluate hypotheses and explain their mechanisms. Conclusion: The sheep is an excellent animal model for evaluation of biomaterial for bone regeneration and dental implant osseointegration. From an ethical point of view, one sheep allows for up to 12 implants per animal, permitting to keep them alive at the end of the experiments. Level of Evidence II, Retrospective Study.

Isoflurane MAC determination in dogs using three intensities of constant-current electrical stimulation.

OBJECTIVES: To compare isoflurane minimum alveolar concentrations (MACs) in dogs determined using three intensities of constant-current electrical stimulation applied at the tail, and thoracic and pelvic limbs, and to compare isoflurane MACs obtained with all combinations of electrical stimulation and anatomic site with those obtained using the tail clamp as the noxious stimulus. STUDY DESIGN: Randomized trial. ANIMALS: Six mixed-breed, adult female dogs aged 1-2 years and weighing 11.1 ± 4.4 kg. METHODS: In each dog, MAC was determined by the bracketing method with the tail clamp (MACTAILCLAMP ), and three electrical currents (10 mA, 30 mA, 50 mA) at three anatomic sites (thoracic limb, pelvic limb, tail). Each MAC achieved with electrical stimulation was compared with MACTAILCLAMP using a mixed-model anova and Dunnett's procedure for multiple comparisons. The effects of current intensity and anatomic site on isoflurane MAC were tested using a mixed-model anova followed by Tukey's test for multiple comparisons (p < 0.05). RESULTS: Mean MACTAILCLAMP was 1.69%. MACs achieved with currents of 30 mA and 50 mA did not differ independently of anatomic site. When currents of 10 mA were applied to the tail and thoracic limb, resulting MACs were lower than those obtained using currents of 30 mA and 50 mA. Currents of 30 mA and 50 mA provided MACs that did not differ from those of MACTAILCLAMP , whereas a current of 10 mA achieved the same result only for the pelvic limb. CONCLUSIONS AND CLINICAL RELEVANCE: Isoflurane MAC is affected by current intensity and anatomic site. Current intensities of 30 mA and 50 mA provided consistent results when applied to the tail, and thoracic and pelvic limbs that did not differ from those obtained using the tail clamp. Consequently, they can be used in place of the tail clamp in MAC studies in dogs.

SHEEP AS AN EXPERIMENTAL MODEL FOR BIOMATERIAL IMPLANT EVALUATION.

OBJECTIVE: Based on a literature review and on our own experience, this study proposes sheep as an experimental model to evaluate the bioactive capacity of bone substitute biomaterials, dental implant systems and orthopedics devices. The literature review covered relevant databases available on the Internet from 1990 until to date, and was supplemented by our own experience. METHODS: For its resemblance in size and weight to humans, sheep are quite suitable for use as an experimental model. However, information about their utility as an experimental model is limited. The different stages involving sheep experiments were discussed, including the care during breeding and maintenance of the animals obtaining specimens for laboratory processing, and highlighting the unnecessary euthanasia of animals at the end of study, in accordance to the guidelines of the 3Rs Program. RESULTS: All experiments have been completed without any complications regarding the animals and allowed us to evaluate hypotheses and explain their mechanisms. CONCLUSION: The sheep is an excellent animal model for evaluation of biomaterial for bone regeneration and dental implant osseointegration. From an ethical point of view, one sheep allows for up to 12 implants per animal, permitting to keep them alive at the end of the experiments. Level of Evidence II, Retrospective Study.

The sheep as a model for healing studies after partial nephrectomy.

BACKGROUND: The pig has been considered the best model for renal surgery. However, recent research has demonstrated that the kidney of pigs heals differently from that of humans. The objective of this study was to evaluate sheep as an alternative animal model for studying collecting system healing after laparoscopic partial nephrectomy. MATERIALS AND METHODS: The caudal pole of the left kidney was removed from eight female adult domestic sheep using laparoscopic partial nephrectomy. Monopolar energy was used for hemostasis only in the parenchyma, avoiding coagulation near the collecting system, which was left opened. After 14 d, all animals were euthanized, and their left kidney was removed. Serum levels of urea and creatinine were assessed preoperatively and postoperatively (on days 2, 6, 10, and 14), and peritoneal fluid samples were collected during necropsy for urea and creatinine evaluation. An ex vivo retrograde pyelogram was performed, and a retrograde injection of methylene blue ink was administered to evaluate urinary leakage. Samples from the operated pole were analyzed using histologic methods. RESULTS: During necropsy, an urinoma surrounding the operated kidney was observed in one animal. Peritoneal fluid levels of urea and creatinine were elevated. Retrograde pyelograms exhibited contrast-medium extravasation through the operated pole in all kidneys. The opened collecting system was also confirmed by methylene blue ink injection. The operated pole was covered by collagenous tissue and adhered to adjacent organs. CONCLUSIONS: Sheep should be considered as an adequate experimental model for research on collecting system healing after partial nephrectomy.

Efeito do sombreamento e do incrustamento de sementes sobre o desenvolvimento de cultivares de Panicum maximum Jacq / Effect of shade and fouling of seed on the development of cultivars of Panicum maximum Jacq

O objetivo deste trabalho foi verificar o efeito do sombreamento e o incrustamento de sementes sobre o desenvolvimento inicial de cultivares de Panicum maximum. O experimento foi realizado no ano de 2011 no setor de Fitotecnia da Universidade Estadual de Mato Grosso do Sul, Unidade de Aquidauana, sendo o solo da área classificado como Argissolo Vermelho Amarelo distrófico. Foram utilizadas sementes convencionais, com alta pureza física, e sementes incrustadas compostas de material colante de macro e micronutrientes. Utilizaram-se três cultivares de P. maximum: Tanzânia, Mombaça e Massai. Os ambientes de cultivo consistiram de pleno sol (A1) e casa de vegetação com 50% de sombreamento (A2). Por não haver repetições dos ambientes, cada um foi considerado um experimento. Para cada ambiente de cultivo, foi adotado o delineamento experimental de blocos casualizados, em esquema fatorial 2 x 3 (dois tipos de sementes x três cultivares), com quatro repetições, realizando análises de variâncias individuais e análise conjunta dos experimentos para a comparação dos ambientes de cultivo. Foram avaliados os seguintes caracteres morfogênicos: altura da planta (AP), comprimento da lâmina foliar (CLF), número de perfilho (NP), aos 27, 40 e 54 dias após a semeadura (DAS), e massa de matéria seca da parte aérea (MSA) e das raízes (MSR) aos 60 DAS. O ambiente A2 proporcionou melhor desenvolvimento às cultivares de P. maximum. O tratamento com sementes revestidas não influenciou as variáveis mensuradas, com exceção do NP. A cultivar Mombaça apresentou melhor desenvolvimento em relação às demais, porém, para o parâmetro NP, a cultivar Massai obteve os maiores valores.

The objective of this study was to investigate the effect of shading and seed coating on the initial development of cultivars of Panicum maximum. The experiment was conducted in 2011 in the field of Plant Science, State University of Mato Grosso of Sul, Unit Aquidauana, and the soil of the area classified as dystrophic Alfissol. We used conventional seeds with high physical purity, and seed coated bonding material of macro and micronutrients. We used three cultivars of P. maximum: Tanzania, Mombasa and Massai. The cultivation environments consisted of full sun (C1) and a greenhouse with 50% shade (C2). Because there is no repetition of environments, each experiment was considered. For each culture environment, we adopted the randomized block design in a factorial 2 x 3 (two types of seed cultivars x three cultivars) with four replications, performing variance analysis and pooled analysis of individual experiments to compare the environments cultivation. We evaluated the following morphometric characters: plant height (PH), leaf blade length (LBL), number of tillers (NT) at 27, 40 and 54 days after sowing (DAS) and dry mass of shoots (DMS) and roots (DMR) at 60 DAS. The development environment provided better C2 cultivars of P. maximum. The coated seed treatment did not influence the variables measured, with the exception of NT. The cultivar Mombaca showed better development in relation to others, but for the parameter NP, the cultivar Massai obtained the highest values.

Tamoxifen decreases the myofibroblast count in the healing bile duct tissue of pigs.

OBJECTIVE: The aim of this study was to evaluate the effect of oral tamoxifen treatment on the number of myofibroblasts present during the healing process after experimental bile duct injury. METHODS: The sample consisted of 16 pigs that were divided into two groups (the control and study groups). Incisions and suturing of the bile ducts were performed in the two groups. Tamoxifen (20 mg/day) was administered only to the study group. The animals were sacrificed after 30 days. Quantification of myofibroblasts in the biliary ducts was made through immunohistochemistry analysis using anti-alpha smooth muscle actin of the smooth muscle antibody. Immunohistochemical quantification was performed using a digital image system. RESULTS: In the animals treated with tamoxifen (20 mg/day), there was a significant reduction in immunostaining for alpha smooth muscle actin compared with the control group (0.1155 vs. 0.2021, p = 0.046). CONCLUSION: Tamoxifen reduced the expression of alpha smooth muscle actin in the healing tissue after bile duct injury, suggesting a decrease in myofibroblasts in the scarred area of the pig biliary tract. These data suggest that tamoxifen could be used in the prevention of biliary tract stenosis after bile duct surgeries.

Tamoxifen decreases the myofibroblast count in the healing bile duct tissue of pigs

OBJECTIVE: The aim of this study was to evaluate the effect of oral tamoxifen treatment on the number of myofibroblasts present during the healing process after experimental bile duct injury. METHODS: The sample consisted of 16 pigs that were divided into two groups (the control and study groups). Incisions and suturing of the bile ducts were performed in the two groups. Tamoxifen (20 mg/day) was administered only to the study group. The animals were sacrificed after 30 days. Quantification of myofibroblasts in the biliary ducts was made through immunohistochemistry analysis using anti-alpha smooth muscle actin of the smooth muscle antibody. Immunohistochemical quantification was performed using a digital image system. RESULTS: In the animals treated with tamoxifen (20 mg/day), there was a significant reduction in immunostaining for alpha smooth muscle actin compared with the control group (0.1155 vs. 0.2021, p = 0.046). CONCLUSION: Tamoxifen reduced the expression of alpha smooth muscle actin in the healing tissue after bile duct injury, suggesting a decrease in myofibroblasts in the scarred area of the pig biliary tract. These data suggest that tamoxifen could be used in the prevention of biliary tract stenosis after bile duct surgeries.

Avaliação do torque de inserção de implantes autorrosqueantes após diferentes tipos de instrumentação / Evaluation of the insertion torque of self-tapping dental implants after diferents types of instrumentation

O prognóstico e a previsibilidade do sucesso dos implantes dentários estão diretamente relacionados, dentre alguns fatores, com a sua estabilidade primária e o torque de inserção durante a instalação no leito ósseo. Este estudo tem por objetivo avaliar os torques de inserção in vivo, de implantes dentários instalados após três diferentes formas de instrumentação: subinstrumentação, instrumentação padrão e sobreinstrumentação. Foram instalados três implantes em mandíbulas de ovelhas e os torques foram aferidos através de torquímetro digital no momento da instalação. Os implantes testados apresentaram um alto torque de inserção nos três tipos de instrumentações. Conclui-se que estes implantes apresentam alta estabilidade primária mesmo nos casos de sobreinstrumentação.

He prognosis and predictability about the success of dental implants are directly related to the primary stability and insertion torque during installation in the bone bed. This study aims to evaluate the insertion torque in vivo, of dental implants installed after three different forms of instrumentation: short instrumentation, standard instrumentation and over instrumentation. Three implants were installed in sheep’s jaw and torques were measured using digital torque meter during installation. The implants tested showed a high insertion torque in the three types of instrumentations. We conclude that these implants have a high primary stability even in cases of over instrumentation.

The rabbit as an animal model for experimental surgery.

The white New Zealand rabbit (Oryctolagus cuniculus) is frequently used as a model for in vivo studies. However, information on precautions when using this animal as an experimental model is limited. This review of the literature covers the gamut from the selection of the animal model all the way to its death, and describes procedures for transporting, raising, breeding, housing, administering anesthesia and handling so as to rationalize the utilization of this species while exploiting its unique characteristics. Based upon the literature and our own experience with white New Zealand rabbits, we conclude that the rabbit is an adequate model for experimental surgery.

The rabbit as an animal model for experimental surgery / O coelho como modelo animal para cirurgia experimental

The white New Zealand rabbit (Oryctolagus cuniculus) is frequently used as a model for in vivo studies. However, information on precautions when using this animal as an experimental model is limited. This review of the literature covers the gamut from the selection of the animal model all the way to its death, and describes procedures for transporting, raising, breeding, housing, administering anesthesia and handling so as to rationalize the utilization of this species while exploiting its unique characteristics. Based upon the literature and our own experience with white New Zealand rabbits, we conclude that the rabbit is an adequate model for experimental surgery.

O coelho branco da Nova Zelândia (Oryctolagus cuniculus) é freqüentemente utilizado como modelo em estudos in vivo. Contudo, as informações referentes aos cuidados no emprego deste animal como modelo experimental são limitadas. Esta revisão da literatura pretende rever a literatura desde a seleção do modelo animal até a sua morte, enfatizando, os procedimentos para transporte, criação, reprodução, comportamento, acomodação, anestesia e manejo dos animais, de forma a racionalizar a utilização desses animais reconhecendo as características próprias dessa espécie. Conclui-se que o coelho constitui um modelo adequado e viável para cirurgia experimental.

Avaliação histológica comparativa de reparo ósseo em tíbia de coelho tratada com xenoenxertos / Comparative histological evaluation of tibil bone repair in rabbits treated with xenografts

OBJETIVO: Os xenoenxertos são uma alternativa aos enxertos autogênicos e devem ser osteocondutores e biocompatíveis. Um estudo recente demonstrou que as características físicas e químicas das hidroxiapatitas encontradas no comércio não são condizentes com as descrições dos fabricantes. Este estudo avalia a biocompatibilidade e a osteocondução de um xenoenxerto derivado de osso medular bovino. MÉTODOS: Quinze coelhos adultos, pesando entre 2.500g e 3.000g cada um, foram anestesiados e submetidos a procedimentos cirúrgicos para criar três perfurações na tíbia, com 2 mm de diâmetro. Esses orifícios foram preenchidos com coágulo sanguineo, Osseus® e Bio-Oss®. Os animais foram sacrificados depois de 7, 14 e 28 dias. RESULTADOS: A análise histopatológica da interface de osso e biomaterial mostrou ligeira resposta inflamatória depois de 7 dias, que esteve ausente nos períodos subsequentes. Ambos os materiais foram parcialmente substituídos por tecido ósseo diretamente em contato com a superfície dos materiais, sem ocorrência de fibrose. CONCLUSÃO: Concluímos que ambos os materiais são biocompatíveis e absorvíveis, o que permite progressiva aposição óssea na superfície durante todo o período de avaliação.

OBJECTIVE: Xenografts are an alternative to autogenous grafts and must be osteoconductive and biocompatible. A recent study has demonstrated that the physical and chemical characteristics of commercially available hydroxyapatites do not fit the manufacturers' descriptions. This study evaluates the biocompatibility and osteoconduction of a xenograft derived from bovine medullary bone. METHODS: Fifteen adult rabbits weighing between 2,500 g and 3,000 g each were anesthetized and subjected to surgical procedures to create three perforations in the tibia, with a diameter of 2 mm. These were filled with blood clot, Osseus® and Bio-Oss®. The animals were euthanized after 7, 14 and 28 days. RESULTS: Histopathological analysis of the interface between the bone and the biomaterial showed a slight inflammatory response after 7 days, which was absent in the subsequent periods. Both materials were partially replaced by bone tissue directly in contact with the surface of the materials, without the occurrence of fibrosis. CONCLUSION: We concluded that both materials are biocompatible and absorbable, allowing for progressive bone apposition on the surface throughout the evaluation period.

Positive end-expiratory pressure at minimal respiratory elastance represents the best compromise between mechanical stress and lung aeration in oleic acid induced lung injury.

INTRODUCTION: Protective ventilatory strategies have been applied to prevent ventilator-induced lung injury in patients with acute lung injury (ALI). However, adjustment of positive end-expiratory pressure (PEEP) to avoid alveolar de-recruitment and hyperinflation remains difficult. An alternative is to set the PEEP based on minimizing respiratory system elastance (Ers) by titrating PEEP. In the present study we evaluate the distribution of lung aeration (assessed using computed tomography scanning) and the behaviour of Ers in a porcine model of ALI, during a descending PEEP titration manoeuvre with a protective low tidal volume. METHODS: PEEP titration (from 26 to 0 cmH2O, with a tidal volume of 6 to 7 ml/kg) was performed, following a recruitment manoeuvre. At each PEEP, helical computed tomography scans of juxta-diaphragmatic parts of the lower lobes were obtained during end-expiratory and end-inspiratory pauses in six piglets with ALI induced by oleic acid. The distribution of the lung compartments (hyperinflated, normally aerated, poorly aerated and non-aerated areas) was determined and the Ers was estimated on a breath-by-breath basis from the equation of motion of the respiratory system using the least-squares method. RESULTS: Progressive reduction in PEEP from 26 cmH2O to the PEEP at which the minimum Ers was observed improved poorly aerated areas, with a proportional reduction in hyperinflated areas. Also, the distribution of normally aerated areas remained steady over this interval, with no changes in non-aerated areas. The PEEP at which minimal Ers occurred corresponded to the greatest amount of normally aerated areas, with lesser hyperinflated, and poorly and non-aerated areas. Levels of PEEP below that at which minimal Ers was observed increased poorly and non-aerated areas, with concomitant reductions in normally inflated and hyperinflated areas. CONCLUSION: The PEEP at which minimal Ers occurred, obtained by descending PEEP titration with a protective low tidal volume, corresponded to the greatest amount of normally aerated areas, with lesser collapsed and hyperinflated areas. The institution of high levels of PEEP reduced poorly aerated areas but enlarged hyperinflated ones. Reduction in PEEP consistently enhanced poorly or non-aerated areas as well as tidal re-aeration. Hence, monitoring respiratory mechanics during a PEEP titration procedure may be a useful adjunct to optimize lung aeration.

Neuromuscular blocking properties of atracurium during sevoflurane or propofol anaesthesia in dogs.

OBJECTIVE: To quantify the neuromuscular blockade (NMB) produced by atracurium in either sevoflurane or propofol-anaesthetized dogs. ANIMALS: Twelve healthy, female adult mixed-breed dogs weighing 13 +/- 3 kg (range 10-22 kg). MATERIALS AND METHODS: Three doses of atracurium (0.1, 0.2 and 0.3 mg kg(-1)) were tested at 1-week intervals. Anaesthesia was induced with inhaled sevoflurane or intravenous propofol and maintained with end-tidal sevoflurane concentrations of 1.95% (1.25 x MAC) or propofol 0.6 mg kg(-1) minute(-1) respectively. Acceleromyography and train-of-four stimulation of the fibular nerve were used for the assessment of NMB. The percentage depression of the first twitch (T1) and the fourth to the first twitch ratio (T4/T1), the maximum degree of neuromuscular block achieved and surgical muscle relaxation were recorded. Before and during neuro muscular blockade (at 10 minute intervals) body temperature, ECG, arterial blood pressure, inspired and expired CO2 concentrations and SpO2 were recorded. RESULTS: Atracurium produced a dose-dependent duration of NMB in both propofol and sevoflurane-anaesthetized dogs. Duration of block was longer in dogs anaesthetized with sevoflurane. All studied doses of atracurium caused twitch depression > or =95% with little or no cardiovascular changes. CONCLUSIONS: Sevoflurane produces a clinically relevant potentiation of atracurium-induced NMB in dogs compared with propofol. CLINICAL RELEVANCE: Significant differences in the potentiation of NMB drugs are encountered with commonly used anaesthetics in the dog.

Controle automático da ventilação mecânica para minimizar a lesão pulmonar induzida pela ventilação / Automatic control of the mechanical ventilation for minimizing the ventilation induced lung injury

O ajuste de parâmetros dos ventiladores mecânicos pulmonares para evitar a reabertura cíclica de unidades alveolares e pequenas vias aéreas, assim como a hiperdistensão dos septos alveolares, tem sido motivo de atenção nos últimos anos. Este trabalho utiliza um modelo de lesão pulmonar aguda (ALI) em suínos para testar um controlador de ventiladores em malha fechada baseado em regras e modelos discutidos na literatura. Utiliza-se um modelo polinomial da cursa pressão-volume do sistema respiratório para o ajuste da pressão positiva ao final da expiração (PEEP), visando evitar a reabertura cíclica de unidades alveolares, e o ajuste do volume corrente, visando evitar a hiperdistensão pulmonar. Um índice de hiperdistensão baseado na identificação de uma elastância não linear para o sistema respiratório permite o uso do controlador com qualquer forma de onda de ventilação constrolada. Os resultados do controlador proposto foram confrontados com resultados obtidos na ventilação de um grupo controle, manualmente ventilados com base nas mesmas premissas. Como resultado, o controlador automático obteve valores de PEEP dentro da faixa de valores obtidos no grupo controle, porém com menor dispersão. O índice de hiperdistensão calculado ficou abaixo do limiar de hiperdistensão em 5 dos 6 animais do grupo ventilado automaticamente, e em 3 dos 6 animais ventilados do grupo controle. O controlador se comportou de forma estável e os resultados recomendam seu uso em ALI.