A Novel Hypobaric Perfusion Method to Remove Microthrombi in Kidney Grafts with Prolonged Circulatory Arrest: A Pilot Study on a Porcine Model.

Background: Intragraft microthrombi prevent complete organ perfusion, thereby compromising the viability maintained by preservation solutions or machine perfusion. Herein, we developed and evaluated a hypobaric perfusion method for flushing microthrombi from kidney grafts with prolonged circulatory arrest in a porcine model. Methods: Porcine renal grafts with 1-h warm ischemia were flushed with heparin-containing perfusate in a normobaric environment (control group) or a hypobaric environment of -20 to -30 mm Hg (hypobaric perfusion group) for 10 min using a gravity drip from a 1-m height. Perfusion parameters, histological findings in ex vivo blood perfusion experiments (2 control and 4 hypobaric perfusion kidneys), and safety in allogeneic porcine transplantation experiments (1 donor to 2 recipients) were evaluated. Results: The -20 mm Hg hypobaric perfusion group exhibited greater maximal flow than the control group (20.4 versus 6.9 mL/min; P = 0.028). Histological evaluation following 3 h of static cold storage and 10 min ex vivo porcine whole-blood perfusion revealed statistically significant reductions in congestion and edema (1.5 versus 3, and 0.5 versus 4 on a 5-point scale, from 0 to 4; P = 0.014 and 0.006, respectively) in the medulla along with improved ischemia-reperfusion injury scores (4.0 versus 4.7 on a 6-point scale, from 0 to 5; P = 0.004) in the -20 mm Hg hypobaric perfusion group. Kidney grafts perfused under -30 mm Hg hypobaric environment followed by 3 h of static cold storage could be used for porcine allogeneic transplantation without any macroscopic damage to the graft, effect on intraoperative handling, or perioperative adverse events. Thus, the hypobaric perfusion method was considered safe. Conclusions: Perfusion in a hypobaric environment may prevent graft congestion, edema, and further reperfusion injury by flushing out erythrocytes occluding the medullary capillaries, improving marginal renal graft quality, and reducing the number of discarded grafts.

Development and application of a spray tip that enables electrocoagulation of a variety of tissues.

Background: Spray hemostasis is possible using a high-frequency power source from the tip of an electric scalpel; however, the difficulties regarding the uniformity and rapidity of the hemostasis surface remain. This study reports the development of a novel electrocoagulation device tip that can be used in endoscopic and robotic surgeries and can quickly coagulate and hemostat and easily adjust the extent of cauterization and hemostasis while minimizing the depth of thermal injury. Methods: The safety and efficacy of the hemostatic device were verified in a porcine model. A liver surface transection was conducted in vivo and the rapidity of the hemostatic effect of the device was observed. An extracted stomach, kidney, and liver were cauterized ex vivo by three operators with different surgical skills and the effects were analyzed pathologically. In addition, a sacrificed pig cadaver was used to achieve hemostasis at a renal transection site using the multi-spray endoscope tip. Results: An increase in the number of tip terminals expanded the cauterization surface and shortened the cauterization time. In parenchymatous organs, uniform cauterization was possible without increasing the depth of thermal injury. The cauterization depth did not depend on the operator's skill, and the spray coagulation was safe. The variable spray tip allowed for simple hemostasis during open and laparoscopic surgeries. Conclusions: This novel electrocoagulation device tip can be developed as a forceps that can change the spray range and can be used during laparoscopic and robotic surgeries.

Evaluating a New Device for Reducing Second Warm Ischemia During Organ Transplantation in a Porcine Model of Kidney, Heart, and Pancreas Transplantation.

BACKGROUND: Second warm ischemia (SWI) injury between the completion of vascular anastomosis and graft reperfusion has been a longstanding issue in organ transplantation. This type of SWI injury is more severe in transplanted organs more sensitive to temperature changes. This study aimed to present the newly developed OrganPocket, an organ protector made from a proprietary elastomer material, and to demonstrate its efficacy in mitigating SWI injury in clinical kidney transplantation. METHODS: We used an ex vivo porcine organ model to evaluate OrganPocket. After removal, donor organs were immersed and cryopreserved in an organ preservation solution at 4°C before being placed in an OrganPocket. The organ graft and OrganPocket were held for 30 minutes in a 37°C environment mimicking intra-abdominal conditions while temperatures were recorded. Control organs were evaluated under the same conditions without an OrganPocket. In addition, we tested OrganPocket in an intra-abdominal porcine allograft transplant model. RESULTS: The control organ group temperature reached ≥16°C after 30 minutes, while the mean core temperature in the OrganPocket organ group remained at no more than 10°C. Despite an SWI time of approximately 30 minutes, the surface organ temperature upon removal of OrganPocket was 20°C. Cardiac grafts also exhibited a normal heartbeat after reperfusion. CONCLUSIONS: OrganPocket is the world's first device designed to prevent SWI and should also prove useful for heart transplantation.

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.

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.