A rat model of dual-flow liver machine perfusion system.

PURPOSE: As clinical liver perfusion systems use portal vein and artery flow, dual perfusion techniques are required even in small animal models in order to reproduce clinical setting. The aim of this study was to construct a new dual-flow perfusion system in rat model and optimized the oxygen supply to ensure the aerobic metabolization. METHODS: The dual-flow circuit was fabricated using rat liver and whole blood samples as perfusates. The oxygen supply was controlled according to the amount of dissolved oxygen in the perfusate. Perfusate parameters and adenosine triphosphate (ATP) levels were analyzed to evaluate organ function and metabolic energy state. Stored whole blood also tested the suitability as perfusate. RESULTS: Stored blood showed decrease oxygen delivery and liver function compared to fresh blood. Using fresh blood as perfusate with air only, the dissolved oxygen levels remained low and anaerobic metabolism increased. In contrast, with oxygen control at living body level, anaerobic metabolism was well suppressed, and tissue ATP content was increased. CONCLUSIONS: We developed a new dual-flow system that enable to reproduce the clinical settings. The perfusion system showed the possibility to improve the energy metabolic state of the perfused organ under appropriate partial pressure of oxygen.

Preliminary Observations of An Ex Vivo Normothermic Whole Blood Machine Perfusion in An Experimental Liver Transplant Porcine Model.

BACKGROUND: Even though transplantation is an essential treatment with no viable alternatives, a significant worldwide donor shortage persists. In this study, we assessed the metabolism of livers that underwent extended periods of circulatory death and subsequently conducted functional validation through transplantation to explore the feasibility of using livers from an uncontrolled donor after circulatory death (u-DCD). METHODS: A donor model simulating u-DCD was constructed using pigs. The prolonged warm ischemia time (WIT) was set to 60, 120, and 180 minutes, and the liver function was evaluated after 24 hours of perfusion using an originally developed normothermic perfusion system. Based on the results, functional confirmation by transplantation was performed on the 2 groups with prolonged WIT of 60 and 180 minutes. RESULTS: Based on the 24-hour perfusion of the liver alone, we evaluated the function by transplanting the WI 60-minute model and 180-minute model (N = 3 each). Warm ischemia was 73.5 ± 3.7 minutes and 188 ± 3 minutes in the 60-minute model and 180-minute model, respectively. In the model with 60 minutes of WI, one case survived until the endpoint, and 2 cases survived between 8 and 12 hours, whereas, in the model with 180 minutes of WI, they died within 6 hours. CONCLUSION: We constructed a completely uncontrolled circulatory arrest model without anticoagulation and showed the possibility of using u-DCD livers by ex vivo machine perfusion and transplantation.

A rat model of dual-flow liver machine perfusion system

Purpose: As clinical liver perfusion systems use portal vein and artery flow, dual perfusion techniques are required even in small animal models in order to reproduce clinical setting. The aim of this study was to construct a new dual-flow perfusion system in rat model and optimized the oxygen supply to ensure the aerobic metabolization. Methods: The dual-flow circuit was fabricated using rat liver and whole blood samples as perfusates. The oxygen supply was controlled according to the amount of dissolved oxygen in the perfusate. Perfusate parameters and adenosine triphosphate (ATP) levels were analyzed to evaluate organ function and metabolic energy state. Stored whole blood also tested the suitability as perfusate. Results: Stored blood showed decrease oxygen delivery and liver function compared to fresh blood. Using fresh blood as perfusate with air only, the dissolved oxygen levels remained low and anaerobic metabolism increased. In contrast, with oxygen control at living body level, anaerobic metabolism was well suppressed, and tissue ATP content was increased. Conclusions: We developed a new dual-flow system that enable to reproduce the clinical settings. The perfusion system showed the possibility to improve the energy metabolic state of the perfused organ under appropriate partial pressure of oxygen.

Rapid Metabolic Recovery of Donor Circulatory Death Liver Graft Using Whole Blood Perfusion: A Pig Study.

Ex vivo perfusion technology has been actively developed to solve the problem of severe donor shortage. In this study, the ex vivo metabolic characteristics of porcine donation after circulatory death (DCD) liver in short-term perfusion using whole or diluted blood were compared with those of the in vivo transplanted state to evaluate their initial response to resuscitation. METHODS: The porcine DCD model was constructed by clamping the thoracic aorta. After 60 min of blood flow cessation, retrieved livers were flushed with 500 mL of heparin saline (20 000 IU/L) followed by perfusion with 500 mL of cold histidine-tryptophan-ketoglutarate solution. The liver grafts were immersed in cold histidine-tryptophan-ketoglutarate solution for 60 min. Subsequently, normothermic ex vivo perfusion was performed with 20 000 IU/L of heparin added to the collected blood (whole blood group) or medium mixed with 10% whole blood (dilution group) for 3 h. Blood from the portal vein, the hepatic artery, and infra hepatica inferior vena cava was collected hourly and metabolomic analyses were performed. The other liver graft was heterotopically transplanted as a control (in vivo group). Each experiment was conducted once. RESULTS: The guanosine levels demonstrated similar fluctuating trends in the whole blood and in vivo groups. In contrast, the levels increased during the perfusion in the diluted blood group. Fluctuations in choline metabolism demonstrated similar trends in the whole blood and in vivo groups. CONCLUSIONS: Ex vivo machine perfusion with whole blood over a short time resulted in a metabolic trend similar to that in the in vivo model. Further studies in this regard are warranted to progress in the utilization of DCD organs.

Development of a Simple and Active Shunt System in the Anhepatic Stage for Surgical Training of Orthotopic Liver Transplantation.

BACKGROUND: A pig model has been commonly used for technical training for clinical liver transplantation (LT). However, as the healthy pigs have no shunt bypassing the portal vein (PV), it is necessary to complete LT within 30 minutes after shutting off the PV flow. While a model that uses an ex vivo shunt system has been used to alleviate the constraints of the anhepatic phase, it has been often difficult to keep sufficient blood flow rate and prevent the intestinal congestion because the blood vessels were occluded easily with the suction pressure by using the conventional shunt system. METHODS: We designed a portable shunt system and a novel connector that can prevent the blood vessel from occluding. The system can separately control the flow rate of PV and inferior vena cava (IVC) and detect whether the blood vessels were occluded. By reducing the solution volume in the circuit, the effected blood loss ex vivo could be minimized. The stability of this system was verified with 15 medical doctors in an advanced medical professional education course. RESULTS: The system enabled the blood flow to maintain ≥ 20 mL/minute and prevented the intestinal congestion. The perioperative hemodynamics of the recipient were stable without a blood transfusion using 25 to 40 kg pigs. We confirmed that all LT training were completed, even 60 minutes after shutting off the PV flow. CONCLUSIONS: Our system greatly contributed to training on LT for conducting the survival experiments.

Continuous Resuscitation for Porcine Liver Transplantation From Donor After Cardiac Death.

BACKGROUND: To solve the serious donor shortage, the demand is increasing for developing a new method to use the marginal donors, including donors after cardiac death (DCD). Continuous machine perfusion from ex vivo to in situ is a novel technique to overcome warm ischemia during organ grafting as an ischemia-free transplantation. Herein, we tested orthotopic and heterotopic ischemia-free liver transplantation in pigs and evaluated the perfusion characteristics of DCD grafts from ex vivo preservation to implantation. MATERIALS AND METHODS: The demonstration of ischemia-free transplantation was conducted using both orthotopic and heterotopic transplantation models. Warm ischemia time (WIT) was set at 60 minutes or 120 minutes in the DCD models. Recipients were humanely killed 3 days after transplant. Flow rates of portal vein and hepatic artery were set to 0.06 to 0.15 mL/min/g and 0.04 to 0.06 mL/min/g for the liver weight ratio, respectively. RESULTS: Under the stable perfusion rate by machine perfusion, the average hepatic artery pressure of the liver graft after a WIT of 120 minutes was approximately 80 mm Hg higher than after WIT of 60 minutes. The recipient with liver graft of WIT of 60 minutes could not survive overnight. In heterotopic model, the recipient with 1 hour DCD liver survived until humanely killed. CONCLUSIONS: The results of pressure monitoring in our DCD liver graft model indicate that pressures are influenced not only by thrombus formation but also by postmortem rigidity at 2 hours after cardiac death.

Reduction of Warm Ischemia Using a Thermal Barrier Bag in Kidney Transplantation: Study in a Pig Model.

BACKGROUND: With recent advances in surgical technologies, minimally invasive endoscopic and robot-assisted surgical procedures have been introduced. However, prolonged warm ischemic time of the kidneys remains a concern after the organ is removed from a donor and during transplantation into a recipient. We developed a Thermal Barrier Bag (TBB) to prevent warm ischemia during transplantation. To confirm the effectiveness of the TBB, adenosine triphosphate (ATP) activity in the kidney was measured during an ex vivo warming test. An ischemia model porcine kidney was also used as the donor kidney and placed into the TBB; thereafter, the change in temperature at the time of transplantation was examined. MAIN FINDINGS: The purse-like design of the TBB efficiently suppressed heat conduction. A simulation was conducted that allowed the calculation of organ heat transfer condition. In the ex vivo experiment, temperature increases were suppressed in the group whose kidneys were placed in the TBB (30 minutes after transplantation: with TBB = 30°C, without TBB = 35°C). ATP measurements showed that the residual rate was substantially higher in the TBB group (P = .056). Moreover, a temperature suppression effect was demonstrated during the renal transplantation experiment (30 minutes after transplantation: with TBB = 27°C, without TBB = 31°C). CONCLUSION: The ex vivo warming experiment demonstrated that use of TBB slows down the rate of ATP decay in fresh kidneys. In addition, when an ischemic model porcine kidney was placed into the TBB and the temperature change at the time of transplantation was measured, an in vivo temperature-suppressing effect was observed.