Normothermic Ex-vivo Perfusion Research Articles

Hypothermic Ex Vivo Perfusion: Protecting the Donor Heart and the Recipient

We congratulate McLeod et al1 on their study demonstrating successful preservation of hearts for 72 hours utilizing normothermic ex vivo perfusion (NEVP) and plasma cross-circulation, using a live para-corporeal donor sheep. This is a great achievement, because heart preservation was well beyond current clinical storage time limits. However, although the authors note future plans to simplify, the preservation method could be considered methodologically challenging. Additionally, the clinical relevance is somewhat difficult to determine, because of the absence of donor brain death (BD) and related sequelae, well reported to impair organ function.

Normothermic Ex-Vivo Perfusion for Donor Heart Preservation in Transplantation of Patients Bridged with Ventricular Assist Devices

Recently, it has been shown that survival after heart transplantation is impaired in patients bridged with left ventricular assist devices (LVAD), mostly due to increased rates of primary graft dysfunction (PGD). Ex vivo perfusion (EVP) is a graft preservation technique non-inferior to standard cold storage (CS). It allows to maintain the heart in a beating and perfused status during challenging surgical dissection in LVAD patients undergoing heart transplantation, and to reduce ischemic time potentially lowering the risk of PGD. Patients bridged on LVAD and transplanted in two European centers (Udine, Italy and Hanover, Germany) since 2016 were included in the study and prospectively followed. Grafts were transported with EVP using the Organ Care System (Transmedics, Andover, MA) in 44 cases and 21 with CS. The underlying demographics were not different, except for urgency status (86% vs. 57%, p=0.01) and chronic renal failure (59% vs. 29%, p=0.02) in EVP and CS respectively. Median age was 56(21-71) vs. 54(25-65), p=0.73; male sex was 77% vs. 81%, p=0.50 and most frequent ethiology was dilated cardiomyopathy in 73% vs. 52%, p=0.11. No differences were found in donors characteristics, with the employment of extended criteria donors in many cases (41% vs. 43%, p=0.55).Five extended criteria donor hearts were assessed as non-transplantable while on EVP.The remaining grafts were transported for a mean time of 296±64 min in EVP.Ischemic times were significantly shorter in the EVP group (132±29 vs. 223±48 min, p<0.01). The early outcome showed no significant statistical differences between the two groups, but a favourable trend in 30-day mortality after HTx in the EVP group (5% vs. 14%, p=0.19). Severe PGD (11% vs. 19% p=0.32), need of mechanical ventilation >96h (25% vs. 33%, p=0.48), of dialysis (66% vs. 52%, p=0.29), revision for bleeding (16% vs. 19%, p=0.50) and ICU stay (6.1-123 vs. 5.1-195 days, p=0.48) were reported. Furthermore, a trend to better survival at mid-term was found (p=0.25) with 88% vs. 76% survival at 3 years. VAD patients have a high risk of morbidity during HTx. EVP warrants a trend towards improved outcomes in this difficult recipient cohort. The longer available time to perform surgery and the reduced ischemia permit a safer procedure including cases of extended criteria donor employment.

Normothermic machine perfusion of ischaemically damaged porcine kidneys with autologous, allogeneic porcine and human red blood cells.

In porcine kidney auto-transplant models, red blood cells (RBCs) are required for ex-vivo normothermic machine perfusion (NMP). As large quantities of RBCs are needed for NMP, utilising autologous RBCs would imply lethal exsanguination of the pig that is donor and recipient-to-be in the same experiment. The purpose of this study was to determine if an isolated porcine kidney can also be perfused with allogeneic porcine or human RBCs instead. Porcine kidneys, autologous and allogeneic blood were obtained from a local slaughterhouse. Human RBCs (O-pos), were provided by our transfusion laboratory. Warm ischaemia time was standardised at 20 minutes and subsequent hypothermic machine perfusion lasted 1.5–2.5 hours. Next, kidneys underwent NMP at 37°C during 7 hours with Williams' Medium E and washed, leukocyte depleted RBCs of either autologous, allogeneic, or human origin (n = 5 per group). During perfusion all kidneys were functional and produced urine. No macroscopic adverse reactions were observed. Creatinine clearance during NMP was significantly higher in the human RBC group in comparison with the allogeneic group (P = 0.049) but not compared to the autologous group. The concentration of albumin in the urine was significantly higher in the human RBC group (P <0.001) compared to the autologous and allogeneic RBC group. Injury marker aspartate aminotransferase was significantly higher in the human RBC group in comparison with the allogeneic group (P = 0.040) but not in comparison with the autologous group. Renal histology revealed glomerular and tubular damage in all groups. Signs of pathological hyperfiltration and microvascular injury were only observed in the human RBC group. In conclusion, perfusion of porcine kidneys with RBCs of different origin proved technically feasible. However, laboratory analysis and histology revealed more damage in the human RBC group compared to the other two groups. These results indicate that the use of allogeneic RBCs is preferable to human RBCs in a situation where autologous RBCs cannot be used for NMP.

Twenty-four hour ex-vivo normothermic machine perfusion in rat livers.

Ex-vivo liver perfusion (EVLP) is an ideal platform to study liver disease, therapeutic interventions, and pharmacokinetic properties of drugs without any patient risk. Rat livers are an ideal model for EVLP due to less organ quality variability, ease of hepatectomy, well-defined molecular pathways, and relatively low costs compared to large animal or human perfusions. However, the major limitation with rat liver normothermic machine perfusion (NMP) is maintaining physiologic liver function on an ex-vivo machine perfusion system. To address this need, our research demonstrates 24-hour EVLP in rats under normothermic conditions. Early (6 hour) perfusate transaminase levels and oxygen consumption of the liver graft are shown to be good markers of perfusion success and correlate with viable 24-hour post-perfusion histology. Finally, we address overcoming challenges in long-term rat liver perfusions such as rising intrahepatic pressures and contamination, and offer future directions necessary to build upon our work.

Dissemination of a novel organ perfusion technique: ex vivo normothermic perfusion of deceased donor kidneys.

Ex vivo normothermic perfusion (EVNP) technology is a promising means of organ preservation, assessment, and preconditioning prior to kidney transplantation, which has been pioneered by a single group. We describe the challenges of setting up clinical EVNP programs in 2 new centers, as well as early patient outcomes. Governance, training, and logistical pathways are described. In order to demonstrate safety and proficiency in this new technique, early patient outcomes are also described. Patient outcomes included the incidence of primary nonfunction, delayed graft function, graft and patient survival at 1 year. Contralateral kidneys undergoing static cold storage alone were used as a comparator group. Between March 2016 and July 2017, EVNP was performed on 14 kidneys from 12 donors (11 kidneys in center 1, 3 kidneys in center 2). Of the 14 kidneys that underwent EVNP, 12 organs were implanted into 10 recipients. Two pairs of kidneys were implanted as dual grafts and 1 kidney was implanted simultaneously with a pancreas. The remaining 7 kidneys were transplanted as single allografts. Seven pairs of kidneys were available for paired analysis comparing EVNP versus static cold storage. Graft and patient outcomes were comparable between the 2 preservation techniques. The introduction of a clinical EVNP service requires a careful multimodal approach, drawing on the expertise of specialists in transplantation, hematology, and microbiology. Both new clinical EVNP programs demonstrated proficiency and safety when a structured dissemination process was followed.

Ex-vivo Perfusion on Marginal Donors in Heart Transplantation: Clinical Resuts and Pathological Findings

Purpose The ex-vivo normothermic perfusion in Heart Transplantation (HTx) allows to expand the donor pool by reducing the ischemic time and providing graft evaluation. Aim of the study was to compare the traditional cold storage (CS) and ex-vivo normothermic perfusion (EVP) in HTx employing marginal donors. Methods Since 2011, 87 HTx employing marginal donors (age>55 years; expected ischemic time>4h; LVEF 14mm; drug abuse; cardiac arrest; CAD) in standard recipients has been performed, CS was utilized in 70 cases (80%) and EVP in 17 (20%). Pre-operative data, survival and complications at short and long term were analysed. Endomyocardial biopsies were collected at time of organ retrieval (T0), before implantation (T1) and after aortic declamping (T2) for light and electron mycroscopy. Blood samples were collected at T0 and T2 from coronary sinus and peripheral vein for metabolomic evaluation . Results Preoperative data were similar in the two groups. Three organs (15%) were considered not suitable for HTx after EVP. Ischemic time and surgical time were shorter in EVP group, which showed a better short and long term survival: a 5-year survival of 100% vs. 94%, 82% and 73% at 30-day, 1 and 5 years respectively in CS group (p=0.06) and less overall complications (65% vs. 89%, p=0.02). In CS group, endomyocardial biopsies showed a tendency for more prominent myocardial damage after heart reperfusion, especially underlined by mitochondrial and organelles dysfunction (figure1). Conclusion EVP permits to exclude not suitable grafts, to reduce complications and to obtain optimal HTx survival. Pathological findings show a tendency for better myocardial protection.

Keeping It Cool: Extended Myocardial Protection with Topical Cooling to Reduce PGD

Purpose Around 2000 heart transplants are performed in Europe annually. Primary Graft Dysfunction(PGD) rates in Europe are among the highest in the world. The increasing use of marginal donor organs has been suggested as a potential cause. Novel techniques using ex-vivo normothermic perfusion have garnered increasing interest but incur a significant cost. We present a series of patients who underwent heart transplantation at our unit using a novel implantation technique to reduce PGD that is cost-effective and reproducible Methods The donor heart is removed from cold storage and placed in an ice slush basin on arrival to our unit. An aortic cross clamp is applied distal to the donor ascending aorta. An antegrade infusion of 600mls of cold blood cardioplegia is followed by cold oxygenated blood (4-6°C) to achieve a mean aortic root pressure of 60-70 mmHg. This continuous antegrade perfusion is maintained throughout the left atrium and aortic anastomosis with a left ventricular vent in situ. A warm cardioplegia hotshot is infused into the aortic root prior to removal of the recipient aortic cross-clamp. The remaining anastomoses are carried out in the usual fashion sequentially. We compared our experience with this method with the national UK cohort (2015-2016) of patients (Control Group). We performed multivariable logistic regression comparing the two cohorts with PGD as the primary outcome measure. Confounders adjusted for include donor age, recipient age and donor-recipient gender mismatch. Results 139 (71.6 %) patients were male. 46(18.6%) of the patients had ischemic cardiomyopathy. The odds ratio of PGD in the control group was 2.99 (95% CI 1.02- 8.75) when compared to the Extended Cooling. Conclusion This novel approach is associated with significant reductions in PGD rates post-transplantation likely due to the shorter warm ischemic time. Larger studies are needed to show differences after further adjustment for known confounders of PGD. We believe this novel technique is safe, cost-effective and reproducible. Around 2000 heart transplants are performed in Europe annually. Primary Graft Dysfunction(PGD) rates in Europe are among the highest in the world. The increasing use of marginal donor organs has been suggested as a potential cause. Novel techniques using ex-vivo normothermic perfusion have garnered increasing interest but incur a significant cost. We present a series of patients who underwent heart transplantation at our unit using a novel implantation technique to reduce PGD that is cost-effective and reproducible The donor heart is removed from cold storage and placed in an ice slush basin on arrival to our unit. An aortic cross clamp is applied distal to the donor ascending aorta. An antegrade infusion of 600mls of cold blood cardioplegia is followed by cold oxygenated blood (4-6°C) to achieve a mean aortic root pressure of 60-70 mmHg. This continuous antegrade perfusion is maintained throughout the left atrium and aortic anastomosis with a left ventricular vent in situ. A warm cardioplegia hotshot is infused into the aortic root prior to removal of the recipient aortic cross-clamp. The remaining anastomoses are carried out in the usual fashion sequentially. We compared our experience with this method with the national UK cohort (2015-2016) of patients (Control Group). We performed multivariable logistic regression comparing the two cohorts with PGD as the primary outcome measure. Confounders adjusted for include donor age, recipient age and donor-recipient gender mismatch. 139 (71.6 %) patients were male. 46(18.6%) of the patients had ischemic cardiomyopathy. The odds ratio of PGD in the control group was 2.99 (95% CI 1.02- 8.75) when compared to the Extended Cooling. This novel approach is associated with significant reductions in PGD rates post-transplantation likely due to the shorter warm ischemic time. Larger studies are needed to show differences after further adjustment for known confounders of PGD. We believe this novel technique is safe, cost-effective and reproducible.

Combined Ex Vivo Hypothermic and Normothermic Perfusion for Assessment of High-risk Deceased Donor Human Kidneys for Transplantation.

BackgroundDespite careful clinical examination, procurement biopsy and assessment on hypothermic machine perfusion, a significant number of potentially useable deceased donor kidneys will be discarded because they are deemed unsuitable for transplantation. Ex vivo normothermic perfusion (EVNP) may be useful as a means to further assess high-risk kidneys to determine suitability for transplantation.MethodsFrom June 2014 to October 2015, 7 kidneys (mean donor age, 54.3 years and Kidney Donor Profile Index, 79%) that were initially procured with the intention to transplant were discarded based on a combination of clinical findings, suboptimal biopsies, long cold ischemia time (CIT) and/or poor hypothermic perfusion parameters. They were subsequently placed on EVNP using oxygenated packed red blood cells and supplemental nutrition for a period of 3 hours. Continuous hemodynamic and functional parameters were assessed.ResultsAfter a mean CIT of 43.7 hours, all 7 kidneys appeared viable on EVNP with progressively increasing renal blood flow over the 3-hour period of perfusion. Five of the 7 kidneys had excellent macroscopic appearance, rapid increase in blood flow to 200 to 250 mL/min, urine output of 40 to 260 mL/h and increasing creatinine clearance.ConclusionsFavorable perfusion characteristics and immediate function after a 3-hour course of EVNP suggests that high-risk kidneys subjected to long CIT may have been considered for transplantation. The combined use of ex vivo hypothermic and normothermic perfusion may be a useful strategy to more adequately assess and preserve high-risk kidneys deemed unsuitable for transplantation. A clinical trial will be necessary to validate the usefulness of this approach.

OC55 OUTCOME OF HEART TRANSPLANTATION WITH MARGINAL DONORS: COLD STORAGE VS NORMOTHERMIC PERFUSION

Abstract Background and aim: The ex-vivo normothermic perfusion in Heart Transplantation (HTx) allows to expand the donor pool by reducing the ischemic time and providing graft evaluation. Aim of the study was to compare the traditional cold storage (CS) and ex-vivo normothermic perfusion (EVP) in HTx employing marginal donors. Methods: From 2011 to 2018, 88 HTx employing marginal donors (age&gt;55 years; expected ischemic time&gt;4 h; LVEF&lt;50%; IVS&gt;14 mm; drug abuse; cardiac arrest; CAD) in standard recipients has been performed, 69 (78%) grafts maintained in CS vs. 19 (22%) in EVP. Endomyocardial biopsies were collected at time of organ retrieval, before implantation and after aortic declamping. Results: No pre-operative differences were found in the two groups. Three organs (16%) were considered not suitable for HTx after EVP, avoiding possible Primary Graft Failure. EVP group showed a better outcome: a 5-year survival of 100% vs. 94.2%, 83% and 72% at 30-day, 1 and 5 years respectively in CS group (p = 0.10); less overall complications (50% vs. 89.9%, p &lt; 0.01), IABP need (0 vs. 23.2%, p = 0.02), shorter mechanical ventilation (24 vs. 48 hours, p = 0.04) and ICU stay (5 vs. 6 days, p = 0.07). In CS group, endomyocardial biopsies showed a tendency for more prominent myocardial damage after heart reperfusion, especially underlined by mitochondrial and organelles dysfunction. Conclusions: EVP permits a safe evaluation of marginal donors, excluding not suitable grafts. Moreover, allows to reduce complications and to obtain optimal survival after HTx. Pathological findings show a tendency for better myocardial protection, confirming clinical results.

The effect on early renal function of various dynamic preservation strategies in a preclinical pig ischemia-reperfusion autotransplant model.

The aims of this study were to determine the most optimal timing to start machine perfusion during kidney preservation to improve early graft function and to evaluate the impact of temperature and oxygen supply during machine perfusion in a porcine ischemia-reperfusion autotransplant model. The left kidney of an approximately 40-kg female Belgian Landrace pig was exposed to 30 minutes of warm ischemia via vascular clamping and randomized to 1 of 6 study groups: (1) 22-hour static cold storage (SCS) (n = 6), (2) 22-hour hypothermic machine perfusion (HMP) (n = 6), (3) 22-hour oxygenated HMP (n = 7), (4) 20-hour HMP plus 2-hour normothermic perfusion (NP) (n = 6), (5) 20-hour SCS plus 2-hour oxygenated HMP (n = 7), and (6) 20-hour SCS plus 2-hour NP (n = 6). Graft recovery measured by serum creatinine level was significantly faster for continuous HMP preservation strategies compared with SCS alone and for all end-ischemic strategies. The active oxygenated 22-hour HMP group demonstrated a significantly faster recovery from early graft function compared with the 22-hour nonactive oxygenated HMP group. Active oxygenation was also found to be an important modulator of a faster increase in renal flow during HMP preservation. Continuous oxygenated HMP applied from the time of kidney procurement until transplant might be the best preservation strategy to improve early graft function.

A multicentre randomised controlled trial to compare the efficacy of ex-vivo normothermic machine perfusion with static cold storage in human liver transplantation

A multicentre randomised controlled trial to compare the efficacy of ex-vivo normothermic machine perfusion with static cold storage in human liver transplantation

Normothermic Ex-vivo Liver Perfusion and the Clinical Implications for Liver Transplantation.

Despite significant improvements in outcomes after liver transplantation, many patients continue to die on the waiting list, while awaiting an available organ for transplantation. Organ shortage is not only due to an inadequate number of available organs, but also the inability to adequately assess and evaluate these organs prior to transplantation. Over the last few decades, ex-vivo perfusion of the liver has emerged as a useful technique for both improved organ preservation and assessment of organs prior to transplantation. Large animal studies have shown the superiority of ex-vivo perfusion over cold static storage. However, these studies have not, necessarily, been translatable to human livers. Small animal studies have been essential in understanding and improving this technology. Similarly, these results have yet to be translated into clinical use. A few Phase 1 clinical trials have shown promise and confirmed the viability of this technology. However, more robust studies are needed before ex-vivo liver perfusion can be widely accepted as the new clinical standard of organ preservation. Here, we aimed to review all relevant large and small animal research, as well as human liver studies on normothermic ex-vivo perfusion, and to identify areas of deficiency and opportunities for future research endeavors.

Modified Surgical Technique of Normothermic Ex-Vivo Perfusion Reduces Cold Ischemic Time in Lung Transplantation During the EXPAND Trial

Normothermic ex-vivo perfusion with the Organ Care System (OCS) during the INSPIRE Trial demonstrated reduced primary graft dysfunction (PGD) when compared to cold storage. However en-bloc lung retrieval after OCS perfusion was the standard of care. The cold ischemic time for the second lung was increased waiting for first lung implantation and second lung pneumonectomy. Accordingly, we modified the surgical technique performing a sequential retrieval from the OCS device in an attempt to reduce PGD rates.

Ex-Vivo normothermic perfusion of “Antifreeze” kidneys

Ex-Vivo normothermic perfusion of “Antifreeze” kidneys

Heart Transplantation Using the Normothermic Ex-Vivo Perfusion Device Organ Care System for Donor Heart Preservation - Long-term Outcomes

The aim of this study was to analyze long-term outcomes after heart transplantation (HT) using a normothermic ex-vivo perfusion device the Organ Care System (OCS) for donor heart preservation and compare this with standard cold cardioplegia (CC).

Steroids Limit Myocardial Edema During Ex Vivo Perfusion of Hearts Donated After Circulatory Death

Normothermic exvivo heart perfusion (EVHP) has been shown to improve the preservation of hearts donated after circulatory arrest and to facilitate clinical successful transplantation. Steroids are added to the perfusate solution in current clinical EVHP protocols; however, the impact of this approach on donor heart preservation has not been previously investigated. We sought to determine the impact of steroids on the inflammatory response and development of myocardial edema during EVHP. Thirteen pigs were anesthetized, mechanical ventilation was discontinued, and a hypoxemic cardiac arrest ensued. A 15-minute warm-ischemic standoff period was observed, and then hearts were resuscitated with a cardioplegic solution. Donor hearts were then perfused exvivo in a normothermic beating state for 6 hours with 500 mg of methylprednisolone (steroid: n= 5) or without (control: n= 8). The addition of steroids to the perfusate solution reduced the generation of proinflammatory cytokines (interleukin-6, -8, -1β, and tumor necrosis factor-α) and the development of myocardial edema during EVHP (percentage of weight gain: control= 26% ± 7% versus steroid= 16% ± 10%, p= 0.049). Electron microscopy suggested less endothelial cell edema in the steroid group (injury score: control= 1.8 ± 0.2 versus steroid= 1.2 ± 0.2, p= 0.06), whereas perfusate troponin-I (control= 11.9 ± 1.9 ng/mL versus steroid= 9.5 ± 2.4 ng/mL, p= 0.448) and myocardial function were comparable between the groups. The addition of methylprednisolone to the perfusion solution minimizes the generation of proinflammatory cytokines and development of myocardial edema during normothermic exvivo perfusion of hearts donated after circulatory arrest.

The administration of argon during ex vivo normothermic perfusion in an experimental model of kidney ischemia–reperfusion injury

BackgroundArgon has shown potential as an organoprotective agent in numerous models of ischemia–reperfusion injury (IRI). The aim of this study was to evaluate the effects of argon gas during ex vivo normothermic perfusion (EVNP) in an experimental porcine model of kidney IRI. Materials and methodsAfter a warm ischemia time of 15 min and 17 h of static cold storage, porcine kidneys underwent 1 h of EVNP using leukocyte-depleted blood. During EVNP, kidneys were perfused with a gas composition either of 70% argon (n = 6), 70% nitrogen control (n = 6), or standard 95% oxygen (n = 6) balanced with 5% carbon dioxide. After EVNP, kidneys were reperfused with whole blood under standard conditions for 3 h to assess renal function and injury. ResultsDuring 1-h EVNP, the mean renal blood flow was numerically higher in the argon group (49.2 ± 16.2 mL/min/100 g; P = 0.320) compared with the nitrogen and oxygen groups (42.9 ± 18.64 and 37.71 ± 7.0 mL/min/100 g, respectively). Other measures of renal function and hemodynamics were not significantly different between the argon and control groups during this period.During reperfusion, no significant differences were found in functional parameters or inflammatory markers (P < 0.05). Histologic analysis revealed no significant change in morphology or hypoxia-inducible factor-1 alpha staining between gaseous groups. Nuclear hypoxia-inducible factor-1 alpha staining was observed only after 3 h of reperfusion. ConclusionsOur findings suggest that using 70% argon during 1 h of EVNP does not mediate a measurable organoprotective effect in an experimental porcine model of IRI.

Normothermic Ex-Vivo Perfusion of the Intestine

Purpose: Ischemia reperfusion injury is a major risk factor for short and long-term functional survival after intestinal transplantation. Normothermic machine perfusion is an emerging biotechnology designed to prevent the injury associated with cold storage. This study is the first to describe an experimental model of normothermic ex-vivo perfusion of the intestine. Such an innovative approach is critical for the further improvement in the clinical outcome after transplantation of such a uniquely vulnerable hollow organ. Methods: The intestine of 10 cardiac death pigs were retrieved, flushed with UW solution, and perfused using washed pig RBCs based colloid solution with Hct value of 10–15 % at 37[deg]C for 6-12h. The perfusion circuit consisted of pulsatile pump, heat exchanger, oxygenator, and organ basin. The superior mesenteric artery was cannulated with free drainage of the vein. Mean arterial pressure was 80–100 mmHg with a flow of 0.010-0.014 L/min/kg. Peptide based elemental formula was used for luminal nutrition. The perfusate was analyzed for pH, PO2, PCO2, glucose. Results: Four intestines were used to establish the model (G-1) and the remaining six constitute the study group (G-2). The warm and cold ischemia time, 30 to 58min and 90 to 360min, respectively. G-2 showed more active peristalsis compared to G-1 with minimal edema and better perfusion indices. Vascular resistance was significantly (P=0.05) lower (97 ± 25 vs 203 ± 40 dyn[middot]s/cm5) with higher (P=0.02) pH (7.22 ± 0.04 vs 7.0 ± 0.06) and better (P=0.01) O2 consumption (330 ± 57 vs 107 ± 23 ml/min). Interestingly, the enterocyte glucose production was significantly (P=0.04) higher in G-2 compared to G-1 (293 ± 43.8 vs 107 ± 19.3 mg/dl).FIGURE 1: Superior mesenteric artery resistance, pH, oxygen consumption, and glucose level after 6 hours of normothermic machine perfusion.Conclusion: The technical feasibility of intestinal normothermic ex-vivo perfusion was demonstrated and the physio-metabolic principals were successfully established. The perfusate glucose level is unprecedented reliable bioviability marker. Accordingly, further experimental and future clinical trials are warranted.

Contrast Enhanced Ultrasound (CEUS) Assessment of Normothermic Ex Situ Perfusion Demonstrates Improved Liver Arterial Resistance

Ex situ liver perfusion offers the potential to “recondition” organs prior to transplantation. Putative benefits of perfusion include delivery of oxygen, as well as wash-out of the micro-circulation prior to transplantation. Assessment of “reconditioning” has previously centred around biochemistry, such as lactate clearance. Ex-vivo assessment of liver perfusion by CEUS has not been widely reported in the literature. 7 human livers declined for transplantation underwent ex-vivo normothermic perfusion with a red-cell based perfusate at fixed pressures (arterial pressure 75 mmHg, portal pressure 5 mmHg). Contrast enhanced ultrasound (CEUS) was used to assess the livers at zero, two and six hours. 0.7mls Sonovue was injected in the hepatic artery and portal vein separately to identify circulation specific differences in perfusion. Cineloops acquired in the hepatic hilum using low MI technique had regions of interest placed on the main vessel and the parenchyma to generate perfusion curves (Intensity (Db)/ Time (s)). Area Under the Curve (AUC) was analysed (difference between vessel and parenchyma (dAUC) resistance) to quantify changes in tissue perfusion. During perfusion portal vein vessel flow, as measured by AUC, remained relatively stable across all livers, as did the portal parenchymal AUC (dAUC 471/454/340 at 0/2/6 hours). However, although arterial vessel AUC improved, arterial parenchymal flow improved proportionally more (433/197/39 at 0/2/6 hours). CEUS assessment of a human liver on ex-situ normothermic perfusion is possible. Normothermic ex situ perfusion improves the hepatic arterial vascular tone, but has an even greater effect on parenchymal arterial microcirculation.

The Effects of Normothermic Ex-Situ Perfusion on Liver Elasticity Measurements Using Shearwave Elastography

Ex situ liver perfusion offers the potential to “recondition” organs prior to transplantation. Vasoconstriction during cold storage may be reduced by perfusion, which in turn, should result in a “relaxation” of the liver and decreased stiffness. To our knowledge this is the first report of direct shearwave elastography measurements in human ex-vivo livers on machine perfusion. 9 human livers declined for transplantation underwent ex-vivo normothermic perfusion with a red-cell based perfusate at fixed pressures (arterial pressure 75 mmHg, portal pressure 5 mmHg). Shearwave elastography (ElastPQ, Philips healthcare) was performed at zero, two and six hours in the centre of the right lobe. Six measurements were made at each time interval and the velocities averaged. Other factors were measured such as warm ischaemic time, lactate, bile production and biopsies were taken at regular intervals. Shearwave elasticity measurements were achievable in all livers. Elasticity mean at baseline was 1.932 m/s (SD 0.154 m/s), at two hours 1.652 m/s (0.164 m/s) and at six hours 1.806 m/s (SD 0.137 m/s). Liver elasticity reduced between zero and two hours in almost all livers (8 of 9 livers) and then rose again between two and six hours (6 of 9 livers). This suggests that normothermic perfusion is reducing vasoconstriction and washing out the microcirculation making the liver more compliant in the early phase, however, these effects are diminished in long term perfusion. Shearwave elastography of ex-vivo liver transplants is possible and demonstrates a reduction of liver elasticity in the first two hours of normothermic perfusion.