Browsing by Author "Riveros, Sergio"

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    Development of a Novel Perfusable Solution for ex vivo Preservation: Towards Photosynthetic Oxygenation for Organ Transplantation
    (Frontiers Media SA, 2021) Veloso Gimenez, Valentina; Escamilla, Rosalba; Necuñir, David; Corrales Orovio, Rocio; Riveros, Sergio; Marino, Carlo; Ehrenfeld, Carolina; Guzman, Christian Dani; Boric, Mauricio P.; Rebolledo, Rolando; Egaña, José Tomas
    Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation.
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    Implementación de un modelo porcino de trasplante hepático en Chile
    (Sociedad de Cirujanos de Chile, 2020) Ochoa, Gabriela; Marino, Carlo; Riveros, Sergio; Morales, Emilio; Jarry, Cristian; Viñuela, Macarena; Alegría, Leyla; Zenteno, María Josefina; Martínez Castillo, Jorge; Achurra Tirado, Pablo; Rebolledo Acevedo, Rolando Arturo
    Objetivo: Presentar la implementación del primer modelo porcino de trasplante hepático (TH) en Chile y sus resultados. Material y Método: Se implementó un protocolo quirúrgico y anestésico en el contextode una investigación en perfusión normotérmica hepática financiada por un Fondo Nacional de Desarrollo Científico y Tecnológico. Los cerdos fueron seleccionados por peso (35-40 kilos), en cada experimentose utilizó dos, donante y receptor, sometidos a procura y trasplante respectivamente. El análisis se realizó con estadística descriptiva. Resultados: Se realizaron 26 experimentos (marzo de 2018-octubre de 2019). El protocolo consta de 7 etapas: Preparación, Instrumentalización, Procura o Hepatectomía, Tiempo Anhepático, Etapa de Isquemia-Reperfusión, Monitorización y Eutanasia. Las primeras tres son similares en ambos cerdos, y desde la cuarta en adelante corresponde sólo al receptor. La supervivencia a la cirugíafue de 92,3% (24/26) y al seguimiento de 76,9% (20/26). La mortalidad se produjo por inestabilidad cardiovascular postreperfusión portal. El tiempo quirúrgico promedio fue de 170 min, y el tiempo anhepático de 33 min. La PAM cursó una baja postreperfusión con recuperación al final de la monitorización (67,4 mmHg media) y la tendencia en ph fue a acidosis al final del seguimiento (7,21 media). Se requirió drogas vasoactivas en 12 casos. Discusión: Logramos implementar un modelo experimental simplificado y reproducible de TH sin necesidad de circulación extracorpórea ni puente veno-venoso gracias a la estandarización de la técnica quirúrgica y de los cuidados perioperatorios. Conclusiones: La consolidación de un modelo experimental significa el primer paso en investigación preclínica de nuevas tecnologías asociadas al TH en Chile.
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    Implementation and design of customized ex vivo machine perfusion. Analysis of its first results
    (Wiley, 2021) Riveros, Sergio; Marino, Carlo; Ochoa, Gabriela; Morales, Emilio; Soto, Dagoberto; Alegria, Leyla; Josefina Zenteno, Maria; Branes, Alejandro; Achurra, Pablo; Rebolledo, Rolando A.
    The lack of organs available for transplantation is a global problem. The high mortality rates on the waiting list and the high number of discarded livers are reasons to develop new tools in the preservation and transplantation process. New tools should also be available for low-income countries. This article reports the development of customized normothermic machine perfusion (NMP). An ex vivo dual perfusion machine was designed, composed of a common reservoir organ box (CRO), a centrifugal pump (portal system, low pressure), and a roller pump (arterial system, high pressure). Porcine livers (n = 5) were perfused with an oxygenated normothermic (37celcius) strategy for 3 hours. Hemodynamic variables, metabolic parameters, and bile production during preservation were analyzed. Arterial and portal flow remain stable during perfusion. Total bilirubin production was 11.25 mL (4-14.5) at 180 minutes. The median pH value reached 7.32 (7.25-7.4) at 180 minutes. Lactate values decreased progressively to normalization at 120 minutes. This perfusion setup was stable and able to maintain the metabolic activity of a liver graft in a porcine animal model. Design and initial results from this customized NMP are promising for a future clinical application in low-income countries.
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    Resultados de un programa nacional de trasplante cardiaco pediátrico: fortalezas y debilidades. Results of a national program of pediatric heart transplantation: strengths and weakness.
    (2017) Becker Rencoret, Pedro Antonio; Besa, Santiago; Riveros, Sergio; González Foretic, Rodrigo Vicente; Navia, Alfonso; Dellepiane, Paulina; Springmüller P., Daniel; Urcelay Montecinos, Gonzalo
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    Right Lobe Liver Donation After Bariatric Surgery. A Case Series of 4 Living Donors
    (2022) Garcia, Daniel; Riveros, Sergio; Ochoa, Gabriela; Rebolledo, Patricia; Achurra, Pablo; Briceno, Eduardo; Vinuela, Eduardo; Arab, Juan Pablo; Jarufe, Nicolas; Fernandes, Eduardo; Martinez, Jorge; Dib, Martin
    Background. The increasing prevalence of obesity and need for bariatric surgery as well as the expanding use of living donors for liver transplantation means that potential donors could present with this surgical history. We present 4 cases of liver donors with previous bariatric surgery in our living donor liver transplant program. Methods. A retrospective descriptive analysis of patients with a bariatric surgery history who underwent right hepatectomy in our living donor liver transplant program is presented. Results. Case 1: A 53-year-old man with body mass index (BMI) of 33 who underwent lapa-roscopic sleeve gastrectomy (LSG). Pretransplant BMI was 21.5. Case 2: A 46-year-old woman with a BMI maximum of 40.8 who underwent LSG and required conversion to Roux-en-Y gas-tric bypass. Pretransplant BMI was 35.1. Case 3: A 53-year-old woman with a BMI maximum of 31.6 who underwent LSG. Pretransplant BMI was 24.2. Case 4: A 38-year-old man with a BMI maximum of 41.5 who underwent Roux-en-Y gastric bypass 6 years before the hepatectomy. Pretransplant BMI was 29.4. No complications were observed. Average operative time was 367.5 minutes, with a hospital stay of 5.8 days and 100% graft survival to date. Discussion. Utilization of selected donors with previous bariatric surgery appears to be a safe option and increases the donor pool.