Pleural Effusions Following Liver Transplantation: A Single-Center Experience.

INTRODUCTION: This was a single-center retrospective study to evaluate incidence, prognosis, and risk factors in patients with postoperative pleural effusions, a common pulmonary complication following liver transplantation. METHODS: A retrospective review was performed on 374 liver transplantation cases through a database within the timeframe of January 1, 2009 through December 31, 2015. Demographics, pulmonary and cardiac function testing, laboratory studies, intraoperative transfusion/infusion volumes, postoperative management, and outcomes were analyzed. RESULTS: In the immediate postoperative period, 189 (50.5%) developed pleural effusions following liver transplantation of which 145 (76.7%) resolved within 3 months. Those who developed pleural effusions demonstrated a lower fibrinogen (149.6 ± 66.3 mg/dL vs 178.4 ± 87.3 mg/dL; P = .009), total protein (5.8 ± 1.0 mg/dL vs 6.1 ± 1.2 mg/dL; P = .04), and hemoglobin (9.8 ± 1.8 mg/dL vs 10.3 ± 1.9 mg/dL; P = .004). There was not a statistically significant difference in 1-year all-cause mortality and in-hospital mortality between liver transplant recipients with and without pleural effusions. Liver transplant recipients who developed pleural effusions had a longer hospital length of stay (16.4 ± 10.9 days vs 14.0 ± 16.5 days; P = .1), but the differences were not statistically significant. However, there was a significant difference in tracheostomy rates (11.6% vs 5.4%; P = .03) in recipients who developed pleural effusions compared to recipients who did not. CONCLUSIONS: In summary, pleural effusions are common after liver transplantation and are associated with increased morbidity. Pre- and intraoperative risk factors can offer both predictive and prognostic value for post-transplantation pleural effusions. Further prospective studies will be needed to further evaluate the relevance of these findings to limit instances of postoperative pleural effusions.

The efficacy of HBOC-201 in ex situ gradual rewarming kidney perfusion in a rat model.

Gradual rewarming from hypothermic to normothermic is a novel perfusion modality with superior outcome to sudden rewarming to normothermic. However, the identification of an oxygen carrier that could function at a temperature range from 4 to 7°C or whether it is necessary to use oxygen carrier during kidney rewarming, remains unresolved. This study was designed to test the use of a hemoglobin-based oxygen carrier (HBOC) during gradual kidney rewarming as an alternative to simple dissolved oxygen. In this study, 10 rat kidneys were randomly divided into the control and the HBOC group. In the control group, no oxygen carrier was used during rewarming perfusion and the perfusion solution was oxygenated only by applying diffused carbogen flow. The protocol mimicked a donor after circulatory death (DCD) kidney transplantation, where after 30 minutes warm ischemia and 120 minutes cold storage in University of Wisconsin solution, the DCD kidneys underwent gradual rewarming from 10 to 37°C during 90 minutes with or without HBOC. This was followed by 30 minutes of warm ischemia in room temperature to mimic the anastomosis time and 120 minutes of reperfusion at 37°C to mimic the early post-transplant state of the graft. The HBOC group demonstrated superior kidney function which was highlighted by higher ultrafiltrate production, better glomerular filtration rate and improved sodium reabsorption. There was no significant difference between the 2 groups regarding the hemodynamics, tissue injury, and adenosine triphosphate levels. In conclusion, this study suggests better renal function recovery in DCD kidneys after rewarming with HBOC compared to rewarming without an oxygen carrier.

Synthetic hemoglobin-based oxygen carriers are an acceptable alternative for packed red blood cells in normothermic kidney perfusion.

Normothermic machine perfusion presents a novel platform for pretransplant assessment and reconditioning of kidney grafts. Maintaining the metabolic activity of a preserved graft at physiologic levels requires an adequate oxygen supply, typically delivered by crystalloid solutions supplemented with red blood cells. In this study, we explored the feasibility of using a synthetic hemoglobin-based oxygen carrier (HBOC) in human kidney normothermic perfusion. Fourteen discarded human kidneys were perfused for 6 hours at a mean temperature of 37°C using a pressure-controlled system. Kidneys were perfused with a perfusion solution supplemented with either HBOC (n = 7) or packed red blood cells (PRBC) (n = 7) to increase oxygen-carrying capacity. Renal artery resistance, oxygen extraction, metabolic activity, energy stores, and histological features were evaluated. Throughout perfusion, kidneys from both groups exhibited comparable behavior regarding vascular flow (P = .66), oxygen consumption (P = .88), and reconstitution of tissue adenosine triphosphate (P = .057). Lactic acid levels were significantly higher in kidneys perfused with PRBC (P = .007). Histological findings were comparable between groups, and there was no evidence of histological damage caused by the HBOC. This feasibility experiment demonstrates that a HBOC solution can offer a logistically more convenient off-the-shelf alternative to PRBC in normothermic machine perfusion of human kidneys.

End-ischemic machine perfusion reduces bile duct injury in donation after circulatory death rat donor livers independent of the machine perfusion temperature.

A short period of oxygenated machine perfusion (MP) after static cold storage (SCS) may reduce biliary injury in donation after cardiac death (DCD) donor livers. However, the ideal perfusion temperature for protection of the bile ducts is unknown. In this study, the optimal perfusion temperature for protection of the bile ducts was assessed. DCD rat livers were preserved by SCS for 6 hours. Thereafter, 1 hour of oxygenated MP was performed using either hypothermic machine perfusion, subnormothermic machine perfusion, or with controlled oxygenated rewarming (COR) conditions. Subsequently, graft and bile duct viability were assessed during 2 hours of normothermic ex situ reperfusion. In the MP study groups, lower levels of transaminases, lactate dehydrogenase (LDH), and thiobarbituric acid reactive substances were measured compared to SCS. In parallel, mitochondrial oxygen consumption and adenosine triphosphate (ATP) production were significantly higher in the MP groups. Biomarkers of biliary function, including bile production, biliary bicarbonate concentration, and pH, were significantly higher in the MP groups, whereas biomarkers of biliary epithelial injury (biliary gamma-glutamyltransferase [GGT] and LDH), were significantly lower in MP preserved livers. Histological analysis revealed less injury of large bile duct epithelium in the MP groups compared to SCS. In conclusion, compared to SCS, end-ischemic oxygenated MP of DCD livers provides better preservation of biliary epithelial function and morphology, independent of the temperature at which MP is performed. End-ischemic oxygenated MP could reduce biliary injury after DCD liver transplantation.

Metabolic and lipidomic profiling of steatotic human livers during ex situ normothermic machine perfusion guides resuscitation strategies.

There continues to be a significant shortage of donor livers for transplantation. One impediment is the discard rate of fatty, or steatotic, livers because of their poor post-transplant function. Steatotic livers are prone to significant ischemia-reperfusion injury (IRI) and data regarding how best to improve the quality of steatotic livers is lacking. Herein, we use normothermic (37°C) machine perfusion in combination with metabolic and lipidomic profiling to elucidate deficiencies in metabolic pathways in steatotic livers, and to inform strategies for improving their function. During perfusion, energy cofactors increased in steatotic livers to a similar extent as non-steatotic livers, but there were significant deficits in anti-oxidant capacity, efficient energy utilization, and lipid metabolism. Steatotic livers appeared to oxidize fatty acids at a higher rate but favored ketone body production rather than energy regeneration via the tricyclic acid cycle. As a result, lactate clearance was slower and transaminase levels were higher in steatotic livers. Lipidomic profiling revealed ω-3 polyunsaturated fatty acids increased in non-steatotic livers to a greater extent than in steatotic livers. The novel use of metabolic and lipidomic profiling during ex situ normothermic machine perfusion has the potential to guide the resuscitation and rehabilitation of steatotic livers for transplantation.

Subnormothermic Machine Perfusion of Steatotic Livers Results in Increased Energy Charge at the Cost of Anti-Oxidant Capacity Compared to Normothermic Perfusion.

There continues to be significant debate regarding the most effective mode of ex situ machine perfusion of livers for transplantation. Subnormothermic (SNMP) and normothermic machine perfusion (NMP) are two methods with different benefits. We examined the metabolomic profiles of discarded steatotic human livers during three hours of subnormothermic or normothermic machine perfusion. Steatotic livers regenerate higher stores of ATP during SNMP than NMP. However, there is a significant depletion of available glutathione during SNMP, likely due to an inability to overcome the high energy threshold needed to synthesize glutathione. This highlights the increased oxidative stress apparent in steatotic livers. Rescue of discarded steatotic livers with machine perfusion may require the optimization of redox status through repletion or supplementation of reducing agents.

Single-Center Experience With Liver Transplant Using Donors With Very High Transaminase Levels.

OBJECTIVES: Elevation of transaminases has been used as a marker of hepatic ischemic injury and as a crucial parameter for liver graft assessment. However, analysis of serum transaminases has limitations regarding the quantitative assessment of liver necrosis and is not a reliable predictor of outcomes. MATERIALS AND METHODS: We retrospectively reviewed the medical records of all liver transplants (N = 238) performed at the UMass Memorial Medical Center from 2009 to 2013. RESULTS: Fourteen liver grafts showed high peak aminotransferases alanine aminotransferase (ALT) and aspartate aminotransferase (AST) at > 1000 U/L. This high aminotransferase group was compared with 224 donors with low transaminase levels (ALT/AST < 1000 U/L). The high transaminase donors had a median peak AST level of 3216 U/L (range, 1823-13?030 U/L) and ALT level of 2677 U/L (range, 812-7080 U/L). The high transaminase donors showed higher levels of lactate dehydrogenase, international normalized ratio, total bilirubin, and gamma-glutamyltransferase compared with low transaminase donors; however, only lactate dehydrogenase results reached statistical significance. None of the grafts from the high transaminase donors showed primary nonfunction. Three-year graft and patient survival rates were similar in both groups (75% vs 80% [P = .48] and 72% vs 82% [P = .33], respectively). In an analysis of the discard rate of livers over a 10-year period in the United States using the Scientific Registry of Transplant Recipients database, the discard rate of livers with high aminotransferase levels was 69.14% compared with 22.23% for livers with low transaminase levels. CONCLUSIONS: Liver grafts from donors with high transaminase levels can lead to clinical results that are similar to liver grafts from donors who had lower peak transaminase levels.

A Comparative Study of Single and Dual Perfusion During End-ischemic Subnormothermic Liver Machine Preservation.

BACKGROUND: It remains controversial if arterial perfusion in addition to portal vein perfusion during machine preservation improves liver graft quality. Comparative studies using both techniques are lacking. We studied the impact of using single or dual machine perfusion of donation after circulatory death rat livers. In addition, we analyzed the effect of pulsatile versus continuous arterial flow. METHODS: Donation after circulatory death rat livers (n = 18) were preserved by 6 hours cold storage, followed by 1 hour subnormothermic machine perfusion (20°C, pressure of 40/5 mm Hg) and 2 hours ex vivo warm reperfusion (37°C, pressure of 80/11 mm Hg, 9% whole blood). Machine preservation was either through single portal vein perfusion (SP), dual pulsatile (DPP), or dual continuous perfusion (DCP) of the portal vein and hepatic artery. Hydrodynamics, liver function tests, histopathology, and expression of endothelial specific genes were assessed during 2 hours warm reperfusion. RESULTS: At the end of reperfusion, arterial flow in DPP livers tended to be higher compared to DCP and SP grafts. However, this difference was not significant nor was better flow associated with better outcome. No differences in bile production or alanine aminotransferase levels were observed. SP livers had significantly lower lactate compared to DCP, but not DPP livers. Levels of Caspase-3 and tumor necrosis factor-α were similar between the groups. Expression of endothelial genes Krüppel-like-factor 2 and endothelial nitric oxide synthase tended to be higher in dual perfused livers, but no histological evidence of better preservation of the biliary endothelium or vasculature of the hepatic artery was observed. CONCLUSIONS: This study shows comparable outcomes after using a dual or single perfusion approach during end-ischemic subnormothermic liver machine preservation.

Potential approaches to improve the outcomes of donation after cardiac death liver grafts.

There is a growing discrepancy between the supply and demand of livers for transplantation resulting in high mortality rates on the waiting list. One of the options to decrease the mortality on the waiting list is to optimize organs with inferior quality that otherwise would be discarded. Livers from donation after cardiac death (DCD) donors are frequently discarded because they are exposed to additional warm ischemia time, and this might lead to primary-non-function, delayed graft function, or severe biliary complications. In order to maximize the usage of DCD livers several new preservation approaches have been proposed. Here, we will review 3 innovative organ preservation methods: (1) different ex vivo perfusion techniques; (2) persufflation with oxygen; and (3) addition of thrombolytic therapy. Improvement of the quality of DCD liver grafts could increase the pool of liver graft's for transplantation, improve the outcomes, and decrease the mortality on the waiting list.

Oxygenated Hypothermic Machine Perfusion After Static Cold Storage Improves Hepatobiliary Function of Extended Criteria Donor Livers.

BACKGROUND: The mechanism through which oxygenated hypothermic machine perfusion (HMP) improves viability of human extended criteria donor (ECD) livers is not well known. Aim of this study was to examine the benefits of oxygenated HMP after static cold storage (SCS). METHODS: Eighteen ECD livers that were declined for transplantation underwent ex situ viability testing using normothermic (37 °C) machine perfusion (NMP) after traditional SCS (0 °C-4 °C) for 7 to 9 hours. In the intervention group (n = 6), livers underwent 2 hours of oxygenated HMP (at 12 °C) after SCS and before NMP. Twelve control livers underwent NMP without oxygenated HMP after SCS. RESULTS: During HMP, hepatic ATP content increased greater than 15-fold, and levels remained significantly higher during the first 4 hours of NMP in the HMP group, compared with controls. Cumulative bile production and biliary secretion of bilirubin and bicarbonate were significantly higher after HMP, compared with controls. In addition, the levels of lactate and glucose were less elevated after HMP compared with SCS preservation alone. In contrast, there were no differences in levels of hepatobiliary injury markers AST, ALT, LDH, and gamma-GT after 6 hours of NMP. Hepatic histology at baseline and after 6 hours of NMP revealed no differences in the amount of ischemic necrosis between both groups. CONCLUSIONS: Two hours of oxygenated HMP after traditional SCS restores hepatic ATP levels and improves hepatobiliary function but does not reduce (preexisting) hepatobiliary injury in ECD livers.

Gradual Rewarming with Gradual Increase in Pressure during Machine Perfusion after Cold Static Preservation Reduces Kidney Ischemia Reperfusion Injury.

In this study we evaluated whether gradual rewarming after the period of cold ischemia would improve organ quality in an Isolated Perfused Kidney Model. Left rat kidneys were statically cold stored in University of Wisconsin solution for 24 hours at 4°C. After cold storage kidneys were rewarmed in one of three ways: perfusion at body temperature (38°C), or rewarmed gradually from 10°C to 38°C with stabilization at 10°C for 30 min and rewarmed gradually from 10°C to 38°C with stabilization at 25°C for 30 min. In the gradual rewarming groups the pressure was increased stepwise to 40 mmHg at 10°C and 70 mmHg at 25°C to counteract for vasodilatation leading to low perfusate flows. Renal function parameters and injury biomarkers were measured in perfusate and urine samples. Increases in injury biomarkers such as aspartate transaminase and lactate dehydrogenase in the perfusate were lower in the gradual rewarming groups versus the control group. Sodium re-absorption was improved in the gradual rewarming groups and reached significance in the 25°C group after ninety minutes of perfusion. HSP-70, ICAM-1, VCAM-1 mRNA expressions were decreased in the 10°C and 25°C groups. Based on the data kidneys that underwent gradual rewarming suffered less renal parenchymal, tubular injury and showed better endothelial preservation. Renal function improved in the gradual rewarming groups versus the control group.