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This is a collection of creative nonfiction essays.

O presente estudo objetivou avaliar as alterações hemodinâmicas, de oxigenação, de ventilação e metabólicas em cavalos sedados com a associação de romifidina e tartarato de butorfanol submetidos a pneumotórax unilateral de baixa pressão por 20 minutos. Foram utilizados cinco eqüinos machos, hígidos, de diferentes raças, submetidos a dois procedimentos. No primeiro procedimento (Grupo I) os animais receberam a associação de romifidina (0,06 mg/kg) e tartarato de butorfanol (0,04 mg/kg) por via intravenosa. A coleta de dados foi realizada imediatamente antes da administração dos fármacos e após 10, 30, 40 e 65 minutos. No segundo procedimento (Grupo II), os mesmos animais receberam a associação dos fármacos e foram submetidos a toracoscopia, com a criação de pneumotórax unilateral esquerdo de 20 minutos de duração. A coleta de dados foi realizada imediatamente antes e 10 minutos após sedação; 20 minutos após o início do pneumotórax; 5 e 30 minutos após o término do pneumotórax. Os valores obtidos foram confrontados estatisticamente através de provas paramétricas, com a Análise de Variância seguida do Teste de Tukey para a comparação dos diferentes momentos em cada grupo e teste t-Student entre os dois grupos, adotando-se significância estatística de 5% (p<0,05). No Grupo I observou-se redução significativa da freqüência, débito e índice cardíacos até o término das mensurações. No Grupo II houve redução semelhante, porém o débito e índice cardíacos diminuíram de forma não significativa. Os valores da pressão arterial sistólica, diastólica e média permaneceram constantes no Grupo I, e apresentaram diminuição gradativa no Grupo II, significante somente para pressão arterial sistólica aos 5 e 30 minutos após o pneumotórax, e aos 30 minutos após o pneumotórax para pressão arterial média. O valor médio da pressão de artéria pulmonar apresentou aumento após a sedação apenas no Grupo I. A pressão venosa central apresentou incremento significativo aos 10 e 40 minutos após a sedação no Grupo I, e aos 10 minutos após a sedação e 20 minutos de pneumotórax no Grupo II. O índice de resistência vascular sistêmica apresentou aumento significativo somente no Grupo I após a sedação. Não foram presenciadas alterações significativas nos valores do índice de resistência vascular pulmonar em ambos os grupos. A pressão parcial de oxigênio no sangue arterial reduziu de forma significativa no Grupo II após a sedação e aos 20 minutos de pneumotórax. Também neste grupo, os valores de conteúdo, pressão parcial e saturação de oxigênio no sangue venoso misto reduziram de forma significativa em todos os momentos após a mensuração controle. Em ambos os grupos o índice de oferta de oxigênio diminuiu após a sedação, permanecendo reduzido de forma significativa somente no Grupo I. Os valores da diferença arteriovenosa de oxigênio e da taxa de extração de oxigênio apresentaram elevação significativa após a sedação no Grupo II, que persistiu até o término das mensurações. Em ambos os grupos, as alterações na freqüência respiratória, pressão parcial de dióxido de carbono arterial e pH não foram significativas. O bicarbonato plasmático arterial apresentou aumento significativo 30 minutos após o término do pneumotórax no Grupo II. A partir dos resultados obtidos foi possível concluir que: o pneumotórax unilateral induzido com baixo fluxo e mantido a baixo nível pressórico não leva a alterações hemodinâmicas, de oxigenação, ventilação e metabólicas significativas em eqüinos hígidos. A associação de romifidina e butorfanol conferiu sedação e analgesia suficientes para a realização do procedimento. porém foi a responsável pelas alterações hemodinâmicas e de oxigenação. / The aim of this study was to evaluate changes on hemodynamic, oxygenation, ventilation and metabolic values in horses sedated with romifidine and butorphanol, submitted to a low pressure induced unilateral pneumothorax for 20 minutes. Five healthy male horses, of different breeds, were submitted to two procedures. In the first one (Group I) the horses were treated with the intravenous combination of romifidine (0,06 mg/kg) and butorphanol (0,04 mg/kg). Data were collected immediately before and 10, 30, 40 and 65 minutes after drug application. In the second procedure (Group II), the same horses were treated with the drug combination and were submitted to thoracoscopy, with a left unilateral pneumothorax of 20 minutes long. Data were collected immediately before and 10 minutes after drug application, as well 20 minutes after the beginning of the pneumothorax and 5 and 30 minutes after the end of the pneumothorax. Data were submitted to Analysis of Variance test followed by Tukey?s test to compare different moments in each group and t-Student test between groups, with 5% of significance (p<0,05). In Group I was observed a significantly reduction of the heart rate, cardiac output and cardiac index until the end of the measurements. In Group II there was similar reduction, however the decrease of the cardiac output and cardiac index was not significant. The systolic, diastolic and mean arterial pressure remained constant in Group I, and a gradual decrease was observed in Group II. In this group, a significant decrease of the systolic arterial pressure was present at 5 and 30 minutes after the end of the pneumothorax, and the mean arterial pressure only 30 minutes after the end of the pneumothorax. The mean pulmonary arterial pressure increased after sedation only in Group I. The central venous pressure increased significantly 10 and 40 minutes after sedation in Group I and at 20 minutes after the end of the pneumothorax in Group II. The systemic vascular resistance increased significantly after sedation only in Group I. The pulmonary vascular resistance values did not change significantly in both groups. The arterial partial pressure of oxygen reduced significantly after sedation and at 20 minutes after the end of the pneumothorax in Group II. In this group a significant decrease of mixed venous oxygen content, partial pressure and saturation was present in all moments in relation to baseline values. In both groups the oxygen delivery index reduced after sedation, remaining significantly reduced only in Group I. The arteriovenous oxygen difference and the oxygen extraction ratio increased significantly after sedation in Group II, and persisted until the end of the procedure. In both groups the respiratory rate, the arterial pressure of carbon dioxide and pH did not change significantly. Plasma bicarbonate increased only in Group II 30 minutes after the end of the pneumothorax. In view of the obtained results its possible to conclude that: low pressure unilateral pneumothorax induced with low flow did not induce significant changes in hemodynamic, oxygenation, ventilation and metabolic values in healthy horses. The combination of romifidine and butorphanol provided good sedation and analgesia to the surgery perform, however was the responsible for the hemodynamic and oxygenation changes that occurred.

Residual osteochondral debris represents a clinical problem associated with arthroscopic debridement and curettage of joint surfaces. At the Oregon State University Veterinary Teaching Hospital (OSU-VTH), during a period from January, 1983 to August, 1986, incidence of radiographically recognizable osteochondral debris in the carpal joints of postarthroscopic equine patients was excessive. Uncertainty exists regarding the fate and effects of this debris on the normal equine joint. Reports in human medical literature implicate osteochondral debris as both an inflammatory stimulus and a mechanical abrasive in the pathogenesis of osteoarthrosis. This study was designed to evaluate the fate and effects of surgically implanted autogenous osteochondral fragments, intended to mimic remaining operative debris, on various physical and biochemical parameters of normal equine middle carpal joints over a six month time period. Four autogenous osteochondral fragments, removed from the lateral trochlear ridge of the talus, were arthroscopically placed as loose bodies into a randomly selected middle carpal joint in each of 10 young horses (2 to 4 years old). The contralateral middle carpal joint, subjected to a sham procedure, served as control. Postoperative therapy was consistent with usual treatment of clinical arthroscopic patients. Lameness evaluation, radiographic examination, carpal circumference measurement, and synovial fluid analysis were performed preoperatively and at scheduled intervals postoperatively. After two months of confinement, the horses were subjected to an increasing level of exercise, intended to mimic a four month conditioning program. Animals were euthanatized at 1 month (1), 2 months (2), 4 months (1), and 6 months (6). Gross and microscopic examination of remaining fragments, articular cartilage, and synovial membrane of each middle carpal joint was performed. Clinically, increased joint circumference, effusion, lameness, and radiographic appearance of degenerative joint disease distinguished implanted from control joints over the six month period. Implanted joints were grossly characterized by grooved, excoriated cartilage surfaces and synovium which was thickened, erythematous, and irregular. Loose bodies became adhered to synovium at their subchondral bone surface within four weeks after placement into the joint. At four weeks, bone within fragments was undergoing necrosis, while cartilage was preserved. At eight weeks, fragments were radiographically inapparent, grossly evident as pale plaques on the synovial surface, and composed of dense fibrous connective tissue. Histologically, synovial membrane specimens from implanted joints demonstrated significant (P < 0.05) inflammatory change two months after implantation. Mononuclear cells infiltrated the synovial layers. Significant physical damage (P < 0.05) was apparent within the articular cartilage two and six months after surgery. Chondrocyte degenerative change was significant (P < 0.05) six months after surgery. Generalized reduction in Safranin-O uptake was not apparent within each level of cartilage samples, but focal reduction in staining was readily apparent in cartilage layers adjacent to physical defects. Synovitis, physical articular damage, and focal chondrocyte degenerative change resulted from a combination of 1) direct mechnical abrasion by the implants or implant-derived debris, 2) an induced effect of osteochondral debris on the synovium, 3) synovitis-induced cartilage degeneration, and 4) supraphysiologic loading associated with exercise. In this study, osteochondral loose bodies of a defined size and shape were resorbed by the synovium within two months after joint implantation. These fragments directly and indirectly induced synovitis and significant articular cartilage degeneration. Methods to prevent and reduce residual postoperative debris and damage associated with its presence are discussed. Implementation of this methodology should reduce the potential for subsequent articular pathology. / Graduation date: 1991

The potential use of the macrolide antimicrobial tilmicosin in the horse was assessed by initially reviewing bacterial isolates from equine infections. This demonstrated that respiratory disease due to Gram positive organisms was the most common bacterial infection documented at WCVM. Furthermore, 45% of Streptococcus zooepidemicus isolates were resistant to the commonly used potentiated sulphonamides. <p>It was necessary to first develop and validate a robust HPLC analytical technique to detect tilmicosin in a variety of equine tissues. The methodology was fully validated in plasma and lung with LODs of 13 ng/mL and 181 ng/g respectively.<p>In a preliminary trial, we administered tilmicosin to recently weaned foals at a dose of 4 mg/kg PO sid or 10 mg/kg SC q 72 hrs. The oral dose did not result in detectable tissue concentrations of tilmicosin. The pharmacokinetics of the injectable dose were similar to previous reports in other species. The injectable preparation resulted in severe swelling at the site of injection associated with edema and tissue necrosis. Otherwise, tilmicosin was well tolerated by the foals and no foals developed severe colitis. However, a semi-quantitative fecal bacteriological technique demonstrated marked changes in the normal fecal flora, with profound overgrowth of the Enterbacteriacae and almost complete removal of the normal â-hemolytic streptococci population. No known pathogens were isolated from the feces.<p>In a subsequent study, we investigated the administration of higher doses of oral tilmicosin to unweaned foals to simulate treatment of R. equi. A dose of 40 mg/kg PO sid resulted in detectable plasma concentrations of tilmicosin. Foals were treated at this dose regimen for 2 weeks and sequentially euthanized. Tissue analysis demonstrated concentrations of tilmicosin in tissues similar to those seen with the 10 mg/kg sc dose with a Cmax of 4 µg/g in lung and a MRT which was shorter at 8.8 hrs. The MIC50 of R. equi to tilmicosin was 4 µg/g. Based on pharmacodynamic studies it appears that oral tilmicosin has the potential to be of use in the treatment of R. equi pneumonia in foals. No adverse clinical effects were noted in the foals; however, the fecal flora was again changed by tilmicosin administration. <p>The fecal flora of the unweaned foals was different from that of the older animals with almost no â-haemolytic streptococci and a predominantly Gram negative flora. Disruption of the fecal flora did result in overgrowth of Cl. perfringens which was not associated with disease.<p>In a final study, we compared the effects of tilmicosin and ceftiofur on the fecal flora of adult horses. The fecal flora of the horses receiving tilmicosin was severely disrupted in the same manner as the weaned foals with the added effect of overgrowth of Cl. perfringens. Ceftiofur which is widely regarded as being associated with antimicrobial associated diarrhea had very little effect on the fecal flora.<p>It is concluded that oral tilmicosin shows potential for the treatment of R. equi pneumonia in young foals. However, care should be taken due to possibility of developing colitis. The drugs use should be avoided in older horses due to the very real risk of developing acute bacterial colitis. The injectable preparation should not be used in horses due to the severity of the reaction at the injection site.

The potential use of the macrolide antimicrobial tilmicosin in the horse was assessed by initially reviewing bacterial isolates from equine infections. This demonstrated that respiratory disease due to Gram positive organisms was the most common bacterial infection documented at WCVM. Furthermore, 45% of Streptococcus zooepidemicus isolates were resistant to the commonly used potentiated sulphonamides. <p>It was necessary to first develop and validate a robust HPLC analytical technique to detect tilmicosin in a variety of equine tissues. The methodology was fully validated in plasma and lung with LODs of 13 ng/mL and 181 ng/g respectively.<p>In a preliminary trial, we administered tilmicosin to recently weaned foals at a dose of 4 mg/kg PO sid or 10 mg/kg SC q 72 hrs. The oral dose did not result in detectable tissue concentrations of tilmicosin. The pharmacokinetics of the injectable dose were similar to previous reports in other species. The injectable preparation resulted in severe swelling at the site of injection associated with edema and tissue necrosis. Otherwise, tilmicosin was well tolerated by the foals and no foals developed severe colitis. However, a semi-quantitative fecal bacteriological technique demonstrated marked changes in the normal fecal flora, with profound overgrowth of the Enterbacteriacae and almost complete removal of the normal â-hemolytic streptococci population. No known pathogens were isolated from the feces.<p>In a subsequent study, we investigated the administration of higher doses of oral tilmicosin to unweaned foals to simulate treatment of R. equi. A dose of 40 mg/kg PO sid resulted in detectable plasma concentrations of tilmicosin. Foals were treated at this dose regimen for 2 weeks and sequentially euthanized. Tissue analysis demonstrated concentrations of tilmicosin in tissues similar to those seen with the 10 mg/kg sc dose with a Cmax of 4 µg/g in lung and a MRT which was shorter at 8.8 hrs. The MIC50 of R. equi to tilmicosin was 4 µg/g. Based on pharmacodynamic studies it appears that oral tilmicosin has the potential to be of use in the treatment of R. equi pneumonia in foals. No adverse clinical effects were noted in the foals; however, the fecal flora was again changed by tilmicosin administration. <p>The fecal flora of the unweaned foals was different from that of the older animals with almost no â-haemolytic streptococci and a predominantly Gram negative flora. Disruption of the fecal flora did result in overgrowth of Cl. perfringens which was not associated with disease.<p>In a final study, we compared the effects of tilmicosin and ceftiofur on the fecal flora of adult horses. The fecal flora of the horses receiving tilmicosin was severely disrupted in the same manner as the weaned foals with the added effect of overgrowth of Cl. perfringens. Ceftiofur which is widely regarded as being associated with antimicrobial associated diarrhea had very little effect on the fecal flora.<p>It is concluded that oral tilmicosin shows potential for the treatment of R. equi pneumonia in young foals. However, care should be taken due to possibility of developing colitis. The drugs use should be avoided in older horses due to the very real risk of developing acute bacterial colitis. The injectable preparation should not be used in horses due to the severity of the reaction at the injection site.

Equine gastric ulcer syndrome (EGUS) is common amongst equine athletes of various disciplines and linked to decreased performance. Prevalence among racehorses has been reported to be over 90%, performance horses at 60%, and endurances horses at about 70%. In swine, concentrate form and smaller particle size increase gastric ulceration; thus, the objective of this study was to investigate the effect of concentrate type on EGUS. Quarter Horse yearlings (n=19; 12-18 mo) were blocked by initial EGUS score on a scale of 0 to 4 (0= no ulceration or hyperkeratosis, 4= extensive, deep ulceration) and sex, and utilized in a 77-d cross-over design with two 28-d periods separated by a 21-d washout period. During the first 28-d period, horses were separated into 1 of 2 treatment groups that were all fed Bermuda grass hay and either a commercially available pelleted or textured concentrate. After the initial 28-d period, horses were all fed pelleted feed and Bermuda grass hay for a 21-d washout period then treatment groups were switched for the final 28-d period. Baseline EGUS scores were not different between horses assigned to either treatment (mean 1.1); however, upon treatment, horses fed textured feed acquired a reduced incidence of ulceration as compared to those fed pelleted (mean score of 1.6 vs 1.1, respectively; P =0.02). Degree and incidence of ulceration was influenced by concentrate form; yearlings fed pelleted feed had higher ulcer scores then those fed textured feed. Therefore, the findings of this study suggests that textured feed may be a effective management tool to aid in the reduction of severity in horses afflicted with EGUS.