Orthotopic liver transplantation (OLT) is an effective treatment for patients with advanced primary biliary cirrhosis (PBC). We have conducted a retrospective analysis of 400 consecutive patients transplanted for PBC between 1983 and 1999. Mean follow-up was 56 months. The proportion of patients grafted for PBC fell progressively, from 35% in 1990 (n ‫؍‬ 80) to 21% in 1999 (n ‫؍‬ 111); comparison of patients grafted in the 2 decades showed that the median age increased from 53 to 56 years and the median serum bilirubin at transplantation fell from 270 mol/L to 132 mol/L. The overall actuarial patient and graft survival at 1, 5, and 10 years is 83%, 78%, and 67% and 82%, 75%, and 61%, respectively. The net gain in 5-year survival compared with predicted survival in the absence of transplantation fell from 37% (range, 82%-90%) to 16% (range, 91%-99%). Multiple organ failure (16.1%) and sepsis (9.6%) were the major causes of early deaths (<6 months). Recurrent PBC, diagnosed on allograft histology, was found in 68 (17%) patients, at a mean time of 36 months. We were unable to identify any pretransplantation donor or recipient factor, which identified those patients at risk of recurrence, although recurrence was much earlier and more frequently seen in patients receiving tacrolimus (P ‫؍‬ .04). PBC remains a good indication for liver transplantation, with excellent survival rates. The age at transplantation increased although patients tended to be grafted earlier. Survival rates have increased although there is a reduction in the survival benefit. Recurrence may be common, but does not seem to affect medium-term graft survival. (HEPATOLOGY 2001;33:22-27.)Orthotopic liver transplantation (OLT) in humans was first successfully reported by Starzl in 1968 1 ; in the early years, few patients were transplanted and survival rates were poor. With increasing experience; better selection; improved surgical, anesthetic, and microbiological techniques; and the introduction of potent immunosuppressive agents, results have improved considerably. As results have improved, patients have been offered transplantation when they are less ill and more likely to withstand the stresses of the procedure and the postoperative period.Primary biliary cirrhosis (PBC) has been one of the most common indications for liver transplantation in adults. 2 Although the pathogenesis remains uncertain and medical therapy, at best, only slows progression of the disease, the natural history is well understood and there are several prognostic models that have been developed to predict not only survival in the absence of transplantation but also survival after transplantation. 3,4 The indications for transplantation are relatively well defined: either a poor quality of life, usually because of intractable lethargy or pruritus, or an anticipated length of life less than 1 year. 5

Esse trabalho descreve um experimento simples e de fácil execução, destinado ao estudo da transferência de calor e massa por meio de uma aula prática. Tal estudoé realizado a partir da fusão de uma placa de gelo, ao ar ambiente, e com base na avaliação quantitativa do calor transferido por radiação, convecção e condensação de vapor d água sobre a superfície dessa placa. Os valores teóricos, previstos a partir de equações relativas a esses processos de transferência de calor e massa, são comparados com dados experimentais relativosà taxa mássica de fusão dessa placa. A facilidade na execução dos ensaios e a simplicidade do equipamento empregado torna esse experimento uma atividade prática de fácil implementação em disciplinas que tratam da transferência de calor e massa. Além disso, a concordância entre valores teórico e experimental da taxa de transferência de calor e massa, e a metodologia empregada na análise e quantificação dessa taxa, viabilizam o experimento proposto como uma ferramenta pedagógica eficiente para o estudo desse tema. Palavras-chave: transferência de calor e massa, fusão de uma placa de gelo, radiação, convecção, condensação de vapor d'água.This work describes a simple and easy-to-perform experiment, destined to the study of the heat and mass transfer by means of a practical class. This study is carried out from the melting of an ice sheet into ambient air and based on the quantitative evaluation of the heat transferred by radiation, convection and condensation of water vapor on the surface of that plate. The theoretical values, predicted from equations related to these processes of heat and mass transfers, are compared with experimental data concerning the melting mass rate of this plate. The ease of running the tests and the simplicity of the equipment employed makes this experiment a practical activity that is easy to implement in disciplines dealing with heat and mass transfer. In addition, the agreement between theoretical and experimental values of the heat and mass transfer rate, and the methodology used in the analysis and quantification of this rate, make feasible the proposed experiment as an efficient pedagogical tool to study this subject.

No abstract

Liver transplantation is now widely recognised as an effective treatment option for patients with advanced liver disease. Many units now achieve greater than 85% survival at 1 year, with the majority of patients having a high quality of life. The maintenance of a high quality of life requires careful clinical management to ensure that the continued maintenance of excellent liver graft function is not achieved at the expense of immunosuppressive drug complications or morbidity. Acute liver rejection will occur in between 30 to 45% of patients, although with modern immunosuppressive protocols, usually combining one of the calcineurin agents, either cyclosporin or tacrolimus, with both azathioprine and corticosteroids (prednisolone) ensures that relatively few grafts are lost from severe acute rejection. While the incidence and severity of acute rejection may be one factor in raising the risk of chronic rejection, it may not be the principal one in many patients. It is important to recognise that the frequency of rejection also varies with the primary underlying liver disease, with patients with hepatitis B or alcoholic liver disease having relatively low rejection rates, compared with patients with primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC), which range between 20 to 70%. Chronic rejection will account for some 5% of grafts lost in the first 3 to 5 years. Indeed, there is some evidence that the incidence of chronic rejection is actually declining over the past few years. While the reason for this apparent decline is uncertain, and it could relate to better immunosuppression management, or more likely to the growing recognition that chronic graft dysfunction may be due to recurrent liver disease, such as autoimmune hepatitis, PBC, PSC, or recurrent hepatitis C. The differentiation of recurrent primary liver disease from chronic rejection can prove to be very difficult in clinical practice. Thus, the clinician must carefully monitor liver and graft function, evaluate any biochemical changes, and try to reach a clear diagnosis before considering any modification of immunosuppressive schedules.

Nesse trabalho é descrito um experimento quantitativo destinado a avaliar a transferência de calor durante o resfriamento de um cilindro de aço e comparar os resultados experimentais com valores previstos em modelos de convecção e radiação do calor. Além de executar os ensaios, o aluno é requisitado a confeccionar uma planilha eletrônica que detalha os cálculos realizados e avalia a consistência dos resultados. O experimento foi concebido para ser facilmente implementado em aulas práticas de cursos de graduação; e, nesse intuito, buscou-se utilizar materiais e equipamentos que viabilizem a realização de ensaios simples e de fácil execução. Os resultados obtidos são satisfatórios e propiciam uma análise quantitativa sobre os mecanismos envolvidos na transferência de calor num sistema físico real.