Assessment of hemodynamic and blood parameters that may reflect macroscopic quality of porcine kidneys during normothermic machine perfusion using whole blood.

PURPOSE: Using ex vivo normothermic machine perfusion (NMP) with whole blood we assessed marginal porcine kidneys under reperfusion. The aim was to link measureable machine and clinical blood parameters with the currently used visual assessment. This could serve as a baseline for a standardized evaluation score to identify potentially transplantable kidneys in the future. METHODS: Kidneys and autologous whole blood were procured from slaughterhouse pigs (n = 33) and were perfused for 4 h using NMP. The hemodynamic parameters arterial pressure (AP), renal blood flow (RBF) and intrarenal resistance (IRR) were measured. Activity of aspartate transaminase (AST), gamma-glutamyltransferase (GGT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and lactate were assessed in blood at 0/1/2/4 h. Kidneys were grouped into "potentially transplantable" (PT) or "not transplantable" (NT) based on their overall macroscopic appearance after NMP by an experienced physician. RESULTS: PT-kidneys (n = 20) had a significantly lower IRR and higher RBF than NT-kidneys (n = 13). GGT, ALP and LDH did not differ significantly, but at 4 h, AST was significantly higher in PT-kidneys compared to NT-kidneys. Lactate levels kept increasing during NMP in NT-kidneys and were significantly higher at 1/2/4 h than in PT-kidneys. CONCLUSION: The immediately assessed macroscopic aspects of examined kidneys correlated with hemodynamic parameters, increased lactate and lower AST in this study. In the future, NMP with whole blood could be a useful tool to extend the donor pool by allowing the assessment of otherwise unknown characteristics of marginal kidneys before transplantation.

Ex vivo heart perfusion: an updated systematic review.

Due to the discrepancy between patients awaiting a heart transplant and the availability of donor hearts, strategies to expand the donor pool and improve the transplant's success are crucial. This review aims to summarize current knowledge on the ex vivo heart preservation (EVHP) experience as an alternative to standard cold static storage (CSS). EVHP techniques can improve the preservation of the donor's heart before transplantation and allow for pre-transplant organ evaluation.

Impact of Pulsatile Machine Perfusion on Posttransplant Recovery in Asystole Donation: Organ Optimization and the Future of Renal Transplantation.

OBJECTIVES: With the increase in life expectancy and the aging of the population, chronic kidney disease has become increasingly prevalent in our environment. Kidney transplantation remains the gold standard treatment for end-stage renal disease, but the supply of renal grafts has not been able to keep pace with growing demand. Because of this rationale, organ selection criteria have been extended (expanded criteria donation), and alternative donation types, such as donation after circulatory death, have been evaluated. These approaches aim to increase the pool of potential donors, albeit with organs of potentially lower quality. Various forms of donations, including donation after circulatory death, have also undergone assessment. This approach aims to augment the pool of potential donors, notwithstanding the compromised quality of organs associated with such methods. Diverse strategies have been explored to enhance graft function, with one of the most promising being the utilization of pulsatile machine perfusion. MATERIALS AND METHODS: We conducted a retrospective analysis on 28 transplant recipients who met the inclusion criterion of sharing the same donor, wherein one organ was preserved by cold storage and the other by pulsatile machine perfusion. We performed statistical analysis on posttransplant recovery parameters throughout the patients' hospitalization, including admission and discharge phases. RESULTS: Statistically significant differences were noted in delayed graft function (P = .04), blood transfusions requirements, and Clavien-Dindo complications. Furthermore, an overall trend of improvement in discharge parameters and hospital stay was in favor of the pulsatile machine perfusion group. CONCLUSIONS: The use of pulsatile machine perfusion as a method of renal preservation results in graft optimization, leading to earlier recovery and fewer complications compared with cold storage in the context of donation after circulatory death.

Preservation of Porcine Donation after Circulatory Death (DCD) Liver by Perfusion and Orthotopic Liver Transplantation.

Conventional static cold storage (SCS) exacerbates ischemic injury in the DCD liver, leading to severe complications for transplant recipients. To address this issue, clinical application of MP technology for donor liver preservation is underway. Simultaneously, efforts are focused on the development of various MP instruments, validated through relevant animal model experiments. Effective large animal trials play a pivotal role in clinical applications. However, challenges persist in the ex vivo preservation of DCD livers and the transplantation procedure in pigs. These hurdles encompass addressing the prolonged preservation of donor livers, conducting viability tests, alleviating ischemic injuries, and shortening the anhepatic phase. The use of a variable temperature-controlled MP device facilitates the prolonged preservation of DCD livers through sequential Dual Hypothermic Oxygenated Machine Perfusion (DHOPE) and Normothermic Machine Perfusion (NMP) modes. This protocol enhances the porcine OLTx model by improving the quality of DCD livers, optimizing the anastomosis technique, and reducing the duration of the anhepatic phase.

Modified Langendorff Perfusion Method for Extended Perfusion Times of Rodent Cardiac Grafts.

Despite important advancements in the diagnosis and treatment of cardiovascular diseases (CVDs), the field is in urgent need of increased research and scientific advancement. As a result, innovation, improvement and/or repurposing of the available research toolset can provide improved testbeds for research advancement. Langendorff perfusion is an extremely valuable research technique for the field of CVD research that can be modified to accommodate a wide array of experimental needs. This tailoring can be achieved by personalizing a large number of perfusion parameters, including perfusion pressure, flow, perfusate, temperature, etc. This protocol demonstrates the versatility of Langendorff perfusion and the feasibility of achieving longer perfusion times (4 h) without graft function loss by utilizing lower perfusion pressures (30-35 mmHg). Achieving extended perfusion times without graft damage and/or function loss caused by the technique itself has the potential to eliminate confounding elements from experimental results. In effect, in scientific circumstances where longer perfusion times are relevant to the experimental needs (i.e., drug treatments, immunological response analysis, gene editing, graft preservation, etc.), lower perfusion pressures can be key for scientific success.

Exploring Alternative Perfusion Solutions Using Next-Generation Polymerized Hemoglobin-Based Oxygen Carriers in a Model of Rat Ex Vivo Lung Perfusion.

Lung transplantation is hampered by the lack of suitable donors. Previously, donors that were thought to be marginal or inadequate were discarded. However, new and exciting technology, such as ex vivo lung perfusion (EVLP), offers lung transplant providers extended assessment for marginal donor allografts. This dynamic assessment platform has led to an increase in lung transplantation and has allowed providers to use donors that were previously discarded, thus expanding the donor pool. Current perfusion techniques use cellular or acellular perfusates, and both have distinct advantages and disadvantages. Perfusion composition is critical to maintaining a homeostatic environment, providing adequate metabolic support, decreasing inflammation and cellular death, and ultimately improving organ function. Perfusion solutions must contain sufficient protein concentration to maintain appropriate oncotic pressure. However, current perfusion solutions often lead to fluid extravasation through the pulmonary endothelium, resulting in inadvertent pulmonary edema and damage. Thus, it is necessary to develop novel perfusion solutions that prevent excessive damage while maintaining proper cellular homeostasis. Here, we describe the application of a polymerized human hemoglobin (PolyhHb)-based oxygen carrier as a perfusate and the protocol in which this perfusion solution can be tested in a model of rat EVLP. The goal of this study is to provide the lung transplant community with key information in designing and developing novel perfusion solutions, as well as the proper protocols to test them in clinically relevant translational transplant models.

[Effect of Intrauterine Perfusion of Granulocyte Colony-Stimulating Factor on Endometrium and Blood Flow Parameters in Patients With Thin Endometrium: A Prospective Controlled Clinical Trial]. / å®«è ”çŒæ³¨ç²’ç»†èƒžé›†è½åˆºæ¿€å› å­æ”¹å–„è–„åž‹å­å®«å† è†œæ‚£è€ å† è†œåŠè¡€æµå‚æ•°çš„å‰çž»æ€§ä¸´åºŠå¯¹ç §è¯•éªŒ.

Objective: To investigate the effects of intrauterine perfusion with granulocyte colony-stimulating factor (G-CSF) on the endometrial thickness, volume, and blood flow parameters of patients with thin endometrium and their clinical outcomes. Methods: We designed a prospective non-randomized synchronous controlled trial and recruited patients with thin endometrium who underwent frozen-thawed embryo transfer (FET) at Mianyang Central Hospital between September 1, 2021 and September 1, 2023. They were divided into two groups, an experimental group of patients who received the experimental treatment of intrauterine perfusion with G-CSF and a control group of patients who did not receive the experimental treatment. The general data and the clinical outcomes of the two groups were analyzed and compared. The endometrial thickness, volume and blood flow parameters of patients in the experimental group before and after intrauterine perfusion with G-CSF were analyzed. Results: The clinical data of 83 patients were included in the study. The experimental group included 51 cases, while the control group included 31 cases. There were no significant differences in the baseline data between the two groups. The clinical pregnancy rate of the experimental group (56.86%) was higher than that of the control group (50.00%) and the rate of spontaneous abortion in the experimental group (27.59%) was lower than that in the control group (37.50%), but the differences were not statistically significant (P>0.05). In the experimental group, the postperfusion endometrial thickness ([0.67±0.1] cm) was greater than the preperfusion endometrial thickness ([0.59±0.09] cm), the postperfusion ([1.84±0.81] cm3) was greater than the preperfusion endometrial volume ([1.54±0.69] cm3), and the postperfusion vascularization flow index (VFI) (1.97±2.82) was greater than the preperfusion VFI (0.99±1.04), with all the differences being statistically significant (P<0.05). Conclusion: Intrauterine perfusion with G-CSF can enhance the endometrial thickness, volume, and some blood flow parameters in patients with thin endometrium.

Normothermic liver perfusion derived extracellular vesicles have concentration-dependent immunoregulatory properties.

Extracellular vesicles (EVs) are major contributors to immunological responses following solid organ transplantation. Donor derived EVs are best known for their role in transplant rejection through transferring donor major histocompatibility complex proteins to recipient antigen presenting cells, a phenomenon known as ?cross-decoration'. In contrast, donor liver-derived EVs are associated with organ tolerance in small animal models. Therefore, the cellular source of EVs and their cargo could influence their downstream immunological effects. To investigate the immunological effects of EVs released by the liver in a physiological and transplant-relevant model, we isolated EVs being produced during normothermic ex vivo liver perfusion (NEVLP), a novel method of liver storage prior to transplantation. We found EVs were produced by the liver during NEVLP, and these EVs contained multiple anti-inflammatory miRNA species. In terms of function, liver-derived EVs were able to cross-decorate allogeneic cells and suppress the immune response in allogeneic mixed lymphocyte reactions in a concentration-dependent fashion. In terms of cytokine response, the addition of 1 × 109 EVs to the mixed lymphocyte reactions significantly decreased the production of the inflammatory cytokines TNF-α, IL-10 and IFN-γ. In conclusion, we determined physiologically produced liver-derived EVs are immunologically regulatory, which has implications for their role and potential modification in solid organ transplantation.

[Machine perfusion in transplantation surgery]. / Maschinenperfusion in der Transplantationschirurgie.

The use of machine perfusion in solid organ transplantation has developed tremendously worldwide in recent years. Although the number of randomized controlled trials in the field of organ preservation is still limited, machine perfusion has been shown to be superior to static cold storage of donor organs. Various devices for clinical use with hypothermia or normothermia are already available for most organs. Whether and which perfusion strategy is superior to the others is the subject of current clinical research. This also applies to the further evaluation of possible synergistic effects in the sequential use of the various protocols. The common goal of all dynamic perfusion technologies is to optimize organ preservation between removal and transplantation. By testing the quality of marginal donor organs prior to transplantation, it should also be possible to use these organs without exposing the patient to increased risk. This can lead to a significant expansion of the donor pool. This is particularly important in Germany, where there is an ongoing shortage of organs and restrictive legislation regarding the expansion of the donor pool. Furthermore, the perfusion technology offers the possibility to serve as a platform for other ex situ and in situ therapies on isolated organs. In addition to the conditioning of pre-damaged organs for transplantation, this could lead to further applications in the context of targeted organ therapies and also to improved transplant logistics in the future.

Meta-analysis of intrauterine hCG perfusion efficacy in recurrent implantation failure as defined by ESHRE guidelines.

PURPOSE: This study evaluates the efficacy of intrauterine hCG perfusion for RIF, as defined by ESHRE 2023 guidelines, highlighting hCG as a cost-effective alternative to other immunotherapies, especially suitable for less developed regions. It aims to clarify treatment guidance amidst previous inconsistencies. METHODS: This meta-analysis, registered with PROSPERO (CRD42024443241) and adhering to PRISMA guidelines, assessed the efficacy and safety of intrauterine hCG perfusion in enhancing implantation and pregnancy outcomes in RIF. Comprehensive literature searches were conducted through December 2023 in major databases including PubMed, Web of Science, Embase, the Cochrane Library, and key Chinese databases, without language restrictions. Inclusion and exclusion criteria were strictly aligned with the 2023 ESHRE recommendations, with exclusions for studies lacking robust control, clear outcomes, or adequate data integrity. The risk of bias was evaluated using the Newcastle-Ottawa Scale, ROBINS-I, and RoB2 tools. Data analysis was performed in R using the 'meta' package, employing both fixed and random effect models to account for study variability. Subgroup analyses by dosage, volume, hCG concentration, timing of administration, and type of embryo transfer were conducted to deepen insights, enhancing the reliability and depth of the meta-analysis in elucidating the role of hCG perfusion in RIF treatments. RESULTS: Data from 13 studies, comprising six retrospective and six prospective studies from single centers, along with one multi-center RCT, totaling 2,157 participants, were synthesized to evaluate the effectiveness of intrauterine hCG perfusion in enhancing implantation and pregnancy outcomes in patients with RIF. Significant improvements were observed in clinical pregnancy and embryo implantation rates across various dosages, timing of administration, and embryo developmental stages, without impacting miscarriage rates. Notably, the most significant efficacy within subgroups occurred with a 500 IU dosage and perfusion parameters of ≤ 500µL volume and ≥ 2 IU/µL concentration. Additionally, a limited number of studies showed no significant increases in ectopic pregnancy or multiple pregnancy rates, and a modest improvement in live birth rates, although the small number of these studies precludes definitive conclusions. CONCLUSIONS: The analysis suggests that intrauterine hCG perfusion probably enhances embryo implantation, clinical pregnancy, and live birth rates slightly in RIF patients. Benefits are indicated with a dosage of 500 IU and a maximum volume of 500µL at concentrations of at least 2 IU/µL. However, substantial heterogeneity from varying study types and the limited number of studies necessitate cautious interpretation. These findings underscore the need for more rigorously designed RCTs to definitively assess the efficacy and safety.

Distinctive protein expression in elderly livers in a Sprague-Dawley rat model of normothermic ex vivo liver machine perfusion.

BACKGROUND: Liver grafts are frequently declined due to high donor age or age mismatch with the recipient. To improve the outcome of marginal grafts, we aimed to characterize the performance of elderly vs. young liver grafts in a standardized rat model of normothermic ex vivo liver machine perfusion (NMP). METHODS: Livers from Sprague-Dawley rats aged 3 or 12 months were procured and perfused for 6 h using a rat NMP system or collected as a reference group (n = 6/group). Tissue, bile, and perfusate samples were used for biochemical, and proteomic analyses. RESULTS: All livers cleared lactate during perfusion and continued to produce bile after 6 h of perfusion (614 mg/h). Peak urea levels in 12-month-old animals were higher than in younger animals. Arterial and portal venous pressure, bile production and pH did not differ between groups. Proteomic analysis identified a total of 1477 proteins with oxidoreductase and catalytic activity dominating the gene ontology analysis. Proteins such as aldehyde dehydrogenase 1A1 and 2-Hydroxyacid oxidase 2 were significantly more present in livers of older age. CONCLUSIONS: Young and elderly liver grafts exhibited similar viability during NMP, though proteomic analyses indicated that older grafts are less resilient to oxidative stress. Our study is limited by the elderly animal age, which corresponds to mature but not elderly human age typically seen in marginal human livers. Nevertheless, reducing oxidative stress could be a promising therapeutic target in the future.

A 3D bioreactor model to study osteocyte differentiation and mechanobiology under perfusion and compressive mechanical loading.

Osteocytes perceive and process mechanical stimuli in the lacuno-canalicular network in bone. As a result, they secrete signaling molecules that mediate bone formation and resorption. To date, few three-dimensional (3D) models exist to study the response of mature osteocytes to biophysical stimuli that mimic fluid shear stress and substrate strain in a mineralized, biomimetic bone-like environment. Here we established a biomimetic 3D bone model by utilizing a state-of-art perfusion bioreactor platform where immortomouse/Dmp1-GFP-derived osteoblastic IDG-SW3 cells were differentiated into mature osteocytes. We evaluated proliferation and differentiation properties of the cells on 3D microporous scaffolds of decellularized bone (dBone), poly(L-lactide-co-trimethylene carbonate) lactide (LTMC), and beta-tricalcium phosphate (ß-TCP) under physiological fluid flow conditions over 21 days. Osteocyte viability and proliferation were similar on the scaffolds with equal distribution of IDG-SW3 cells on dBone and LTMC scaffolds. After seven days, the differentiation marker alkaline phosphatase (Alpl), dentin matrix acidic phosphoprotein 1 (Dmp1), and sclerostin (Sost) were significantly upregulated in IDG-SW3 cells (p = 0.05) on LTMC scaffolds under fluid flow conditions at 1.7 ml/min, indicating rapid and efficient maturation into osteocytes. Osteocytes responded by inducing the mechanoresponsive genes FBJ osteosarcoma oncogene (Fos) and prostaglandin-endoperoxide synthase 2 (Ptgs2) under perfusion and dynamic compressive loading at 1 Hz with 5 % strain. Together, we successfully created a 3D biomimetic platform as a robust tool to evaluate osteocyte differentiation and mechanobiology in vitro while recapitulating in vivo mechanical cues such as fluid flow within the lacuno-canalicular network. STATEMENT OF SIGNIFICANCE: This study highlights the importance of creating a three-dimensional (3D) in vitro model to study osteocyte differentiation and mechanobiology, as cellular functions are limited in two-dimensional (2D) models lacking in vivo tissue organization. By using a perfusion bioreactor platform, physiological conditions of fluid flow and compressive loading were mimicked to which osteocytes are exposed in vivo. Microporous poly(L-lactide-co-trimethylene carbonate) lactide (LTMC) scaffolds in 3D are identified as a valuable tool to create a favorable environment for osteocyte differentiation and to enable mechanical stimulation of osteocytes by perfusion and compressive loading. The LTMC platform imitates the mechanical bone environment of osteocytes, allowing the analysis of the interaction with other cell types in bone under in vivo biophysical stimuli.

Coronary Angiography During Ex-Situ Heart Perfusion in a Porcine Model.

Heart transplantation is the gold standard treatment for advanced heart failure. The procurement of extended criteria donors (ECD) increases due to the current organ shortage. Coronary angiography is recommended in ECD at risk for coronary artery disease but is not systematically performed. These hearts are, therefore, either declined for transplant or procured without screening for coronary artery disease. Coronary angiography during normothermic ex-situ heart perfusion (NESP) could be an interesting approach to enhance the rate of ECD procurement and to reduce the risk of primary graft failure in the absence of coronary angiography in ECD. The present protocol aims to provide material details along with optimal imaging views for coronary angiography during NESP. Reproducible angiographic views were observed, including one dedicated to the right coronary artery, two for the left anterior descending artery, two for the circumflex artery, and a spider view. Continuous lactate extraction was observed in all procedures with a final median concentration of 1.10 mmol/L (0.61-1.75 mmol/L) two hours after coronary angiography, consistent with myocardial viability. The median contrast agent volume used for ex-situ imaging of the isolated perfused heart was 48 mL (38-108 mL). This protocol was reproducible for coronary artery imaging and did not impair myocardial viability during NESP.

Recent solid-phase microextraction-based analytical approaches for the profiling of biliary bile acids in pre-transplant assessments of liver grafts subjected to normothermic ex vivo liver perfusion.

BACKGROUND: Liver transplantation is the definitive treatment for end-stage liver failure, but the scarcity of donor organs remains a significant challenge. Leveraging organs from extended criteria donors (ECD) offers a potential avenue to address worldwide shortages, though these organs are more susceptible to post-reperfusion injury. This study explores the use of normothermic ex vivo liver perfusion (NEVLP) as a method for organ preservation - an approach that sustains liver metabolism and facilitates pre-transplant assessments of organ viability via bile analysis. The focal point of this study revolves on the development of analytical methods for determining the bile acid profile throughout the peritransplantation period as a potential indicator of liver function and viability. RESULTS: The study optimized and validated a high-throughput analytical method to quantify selected bile acids in bile samples using a thin-film microextraction-liquid chromatography-mass spectrometry (TFME-LC-MS) platform. Furthermore, it introduced a solid-phase microextraction-microfluidic open interface-mass spectrometry (SPME-MOI-MS) method for rapid direct analysis of bile acid isobar groups. In the animal study, discernible variations in the concentrations of specific bile acids were observed between donors after circulatory death (DCD) and heart-beating donors (HBD), particularly following normothermic perfusion and reperfusion. Noteworthy fluctuations in individual bile acid concentrations were observed throughout the entire organ transplantation process, with taurocholic acid (TCA), glycocholic acid (GCA), and glycochenodeoxycholic acid (GCDCA) emerging as promising indicators of organ quality. The efficacy of the SPME-MOI-MS platform in corroborating these trends highlights its potential for real-time bile acid analysis during liver transplantation procedures. SIGNIFICANCE: Our findings underscore the efficacy of NEVLP in tandem with advanced bile acid analysis methods as a reliable strategy for pre-transplant assessments of organ viability, potentially increasing the use of ECD organs and reducing organ shortages. The ability to monitor bile acid profiles in real-time provides crucial insights into liver function and ischemic injury, making significant strides in improving transplant outcomes and patient survival rates.

Successful Kidney Donation Following Long-Term Normothermic Regional Perfusion: Challenges of the First Uncontrolled Donation After Circulatory Death in Iran.

The global organ donation crisis continues to escalate despite advancements in medical procedures. Uncont-rolled donation after circulatory death provides an alternative method to increase the donor pool, especially for kidney transplants. This case study from Iran offers insights into the complex, yet essential, facets of organ procurement under uncontrolled donation after circulatory death protocols. A 38-year-old woman experienced a severe cerebrovascular accident and subsequent cardiac arrest. She was declared for uncontrolled donation after circulatory death, and her organs were preserved using cardiopulmonary bypass for 6 hours. Notably, her kidneys were successfully removed and transplanted into 2 recipients: a 43-year-old man with chronic kidney disease due to hypertension and a 48-year-old man with chronic kidney disease associated with diabetes mellitus. The first recipient experienced initial complications with kidney function that required a prolonged hospital stay, but he eventually exhibited improved renal function. The second recipient experienced fluctuating kidney function initially, which stabilized, demonstrating the practical viability of kidneys procured through uncontrolled donation after circulatory death. This pioneering case in Iran underscores the potential of uncontrolled donation after circulatory death to expand organ procurement and addresses critical medical, ethical, and legal challenges. We emphasize the need for refined protocols that reduce wait times and improve organ viability, thereby contributing to the broader organ donation network. Future research should focus on enhancement of normothermic regional perfusion techniques to improve outcomes for both donors and recipients.

Ex Situ Left Ventricular Pressure-Volume Loop Analyses for Donor Hearts: Proof of Concept in an Ovine Experimental Model.

Ex situ heart perfusion (ESHP) has emerged as an important strategy to preserve donation after brain death (DBD) and donation after circulatory death (DCD) donor hearts. Clinically, both DBD and DCD hearts are successfully preserved using ESHP. Viability assessment is currently based on biochemical values, while a reliable method for graft function assessment in a physiologic working mode is unavailable. As functional assessment during ESHP has demonstrated the highest predictive value of outcome post-transplantation, this is an important area for improvement. In this study, a novel method for ex situ assessment of left ventricular function with pressure-volume loop analyses is evaluated. Ovine hearts were functionally evaluated during normothermic ESHP with the novel pressure-volume loop system. This system provides an afterload and adjustable preload to the left ventricle. By increasing the preload and measuring end-systolic elastance, the system could successfully assess the left ventricular function. End-systolic elastance at 60 min and 120 min was 2.8 ± 1.8 mmHg/mL and 2.7 ± 0.7 mmHg/mL, respectively. In this study we show a novel method for functional graft assessment with ex situ pressure-loop analyses during ESHP. When further validated, this method for pressure-volume assessments, could be used for better graft selection in both DBD and DCD donor hearts.

Continuous oxygen monitoring to enhance ex-vivo organ machine perfusion and reconstructive surgery.

Continuous oxygenation monitoring of machine-perfused organs or transposed autologous tissue is not currently implemented in clinical practice. Oxygenation is a critical parameter that could be used to verify tissue viability and guide corrective interventions, such as perfusion machine parameters or surgical revision. This work presents an innovative technology based on oxygen-sensitive, phosphorescent metalloporphyrin allowing continuous and non-invasive oxygen monitoring of ex-vivo perfused vascularized fasciocutaneous flaps. The method comprises a small, low-energy optical transcutaneous oxygen sensor applied on the flap's skin paddle as well as oxygen sensing devices placed into the tubing. An intermittent perfusion setting was designed to study the response time and accuracy of this technology over a total of 54 perfusion cycles. We further evaluated correlation between the continuous oxygen measurements and gold-standard perfusion viability metrics such as vascular resistance, with good agreement suggesting potential to monitor graft viability at high frequency, opening the possibility to employ feedback control algorithms in the future. This proof-of-concept study opens a range of research and clinical applications in reconstructive surgery and transplantation at a time when perfusion machines undergo rapid clinical adoption with potential to improve outcomes across a variety of surgical procedures and dramatically increase access to transplant medicine.

A novel translational model of atherosclerosis, the ex vivo pump-perfused amputated human limb model.

The preclinical study of atherosclerosis has traditionally centred around the use of small animal models, translating to large animal models, prior to first-in-man studies. We propose to disrupt this paradigm by designing an ex vivo pump perfused human limb model. The novel model consists of taking a freshly amputated limb and incorporating it into an ex situ pump-perfused bypass system (akin to extracorporeal membrane oxygenation), circulating warmed, oxygenated blood. The circuit incorporates an introducer sheath and guiding catheter for intravascular imaging and X-ray angiography. Regular monitoring is performed using blood gas analysis, aiming for physiological parameters. The model maintains oxygen saturations > 99% for the length of perfusion (up to 6-h). Clinical grade X-ray angiography, intravascular ultrasound and optical coherence tomography have been successfully performed. Indocyanine green, a near-infrared fluorescent dye that localises to atherosclerotic plaque, has been injected into the system and left to circulate for 90-min. Fluorescence reflectance imaging of the dissected arterial bed confirmed uptake in areas of calcific atherosclerotic plaque on intravascular imaging. This is the first demonstration of an ex vivo pump-perfused "living" limb experimental model of atherosclerosis, which shows promise for future studies in translational interventional imaging and molecular targeting.

Spectral characterization of intraoperative renal perfusion using hyperspectral imaging and artificial intelligence.

Accurate intraoperative assessment of organ perfusion is a pivotal determinant in preserving organ function e.g. during kidney surgery including partial nephrectomy or kidney transplantation. Hyperspectral imaging (HSI) has great potential to objectively describe and quantify this perfusion as opposed to conventional surrogate techniques such as ultrasound flowmeter, indocyanine green or the subjective eye of the surgeon. An established live porcine model under general anesthesia received median laparotomy and renal mobilization. Different scenarios that were measured using HSI were (1) complete, (2) gradual and (3) partial malperfusion. The differences in spectral reflectance as well as HSI oxygenation (StO2) between different perfusion states were compelling and as high as 56.9% with 70.3% (± 11.0%) for "physiological" vs. 13.4% (± 3.1%) for "venous congestion". A machine learning (ML) algorithm was able to distinguish between these perfusion states with a balanced prediction accuracy of 97.8%. Data from this porcine study including 1300 recordings across 57 individuals was compared to a human dataset of 104 recordings across 17 individuals suggesting clinical transferability. Therefore, HSI is a highly promising tool for intraoperative microvascular evaluation of perfusion states with great advantages over existing surrogate techniques. Clinical trials are required to prove patient benefit.

A tale of two kidneys, and the case for machine perfusion in South Africa.

Extended-criteria donors (ECDs) are seen as a means of addressing the shortfall in solid-organ availability for transplant. However, the use of ECD kidneys is associated with a greater risk of primary non-function compared with standard-criteria donor kidneys, and a higher discard rate has been described internationally. There seems to be a lack of consensus in the consideration of ECD kidneys for transplant, with reliance often placed on the subjective assessment of individual clinicians. The following case examines the difference in the institutional decision-making process applied to two kidneys from a single donor, and provides an argument for the use of hypothermic machine perfusion in low- to middle-income countries as an efficacious and objective means of assessing ECD kidney suitability.