Reduction of proteolysis by venous-systemic oxygen persufflation during rat liver preservation and improved functional outcome after transplantation

Deregulation of the Purine Pathway in Pre-Transplant Liver Biopsies Is Associated with Graft Function and Survival after Transplantation

The current shortage of livers for transplantation has increased the use of marginal organs sourced from donation after circulatory death (DCD). However, these organs have a higher incidence of graft failure, and pre-transplant biomarkers which predict graft function and survival remain limited. Here, we aimed to find biomarkers of liver function before transplantation to allow better clinical evaluation. Matched pre- and post-transplant liver biopsies from DCD (n = 24) and donation after brain death (DBD, n = 70) were collected. Liver biopsies were analysed using mass spectroscopy molecular phenotyping. Discrimination analysis was used to parse metabolites differentiated between the two groups. Five metabolites in the purine pathway were investigated. Of these, the ratios of the levels of four metabolites to those of urate differed between DBD and DCD biopsies at the pre-transplantation stage (q < 0.05). The ratios of Adenosine monophosphate (AMP) and adenine levels to those of urate also differed in biopsies from recipients experiencing early graft function (EGF) (q < 0.05) compared to those of recipients experiencing early allograft dysfunction (EAD). Using random forest, a panel consisting of alanine aminotransferase (ALT) and the ratios of AMP, adenine, and hypoxanthine levels to urate levels predicted EGF with area under the curve (AUC) of 0.84 (95% CI (0.71, 0.97)). Survival analysis revealed that the metabolite classifier could stratify six-year survival outcomes (p = 0.0073). At the pre-transplantation stage, a panel composed of purine metabolites and ALT could improve the prediction of EGF and survival.

Oxygen Persufflation in Liver Transplantation Results of a Randomized Controlled Trial

Oxygen persufflation has shown experimentally to favorably influence hepatic energy dependent pathways and to improve survival after transplantation. The present trial evaluated oxygen persufflation as adjunct in clinical liver preservation. A total of n = 116 adult patients (age: 54 (23–68) years, M/F: 70/46), were enrolled in this prospective randomized study. Grafts were randomized to either oxygen persufflation for ≥2 h (O2) or mere cold storage (control). Only liver grafts from donors ≥55 years and/or marginal grafts after multiple rejections by other centers were included. Primary endpoint was peak-aspartate aminotransferase (AST) level until post-operative day 3. Standard parameters including graft- and patient survival were analyzed by uni- and multivariate analysis. Both study groups were comparable except for a longer ICU stay (4 versus 3 days) of the donors and a higher recipient age (57 versus 52 years) in the O2-group. Serum levels of TNF alpha were significantly reduced after oxygen persufflation (p < 0.05). Median peak-AST values did not differ between the groups (O2: 580 U/l, control: 699 U/l). Five year graft- and patient survival was similar. Subgroup analysis demonstrated a positive effect of oxygen persufflation concerning the development of early allograft dysfunction (EAD), in donors with a history of cardiopulmonary resuscitation and elevated ALT values, and concerning older or macrosteatotic livers. This study favors pre-implantation O2-persufflation in concrete subcategories of less than optimal liver grafts, for which oxygen persufflation can be considered a safe, cheap and easy applicable reconditioning method.

"Resuscitation" of marginal liver allografts for transplantation with machine perfusion technology

As the rate of medically suitable donors remains relatively static worldwide, clinicians have looked to novel methods to meet the ever-growing demand of the liver transplant waiting lists worldwide. Accordingly, the transplant community has explored many strategies to offset this deficit. Advances in technology that target the ex vivo "preservation" period may help increase the donor pool by augmenting the utilization and improving the outcomes of marginal livers. Novel ex vivo techniques such as hypothermic, normothermic, and subnormothermic machine perfusion may be useful to "resuscitate" marginal organs by reducing ischemia/reperfusion injury. Moreover, other preservation techniques such as oxygen persufflation are explored as they may also have a role in improving function of "marginal" liver allografts. Currently, marginal livers are frequently discarded or can relegate the patient to early allograft dysfunction and primary non-function. Bench to bedside advances are rapidly emerging and hold promise for expanding liver transplantation access and improving outcomes.

Graft reconditioning with nitric oxide gas in rat liver transplantation from cardiac death donors

BACKGROUND

Liver transplant outcomes using grafts donated after cardiac death (DCD) remain poor.

METHODS

We investigated the effects of ex vivo reconditioning of DCD grafts with venous systemic oxygen persufflation using nitric oxide gas (VSOP-NO) in rat liver transplants. Orthotopic liver transplants were performed in Lewis rats, using DCD grafts prepared using static cold storage alone (group-control) or reconditioning using VSOP-NO during cold storage (group-VSOP-NO). Experiment I: In a 30-min warm ischemia model, graft damage and hepatic expression of inflammatory cytokines, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and endothelin-1 (ET-1) were examined, and histologic analysis was performed 2, 6, 24, and 72 hr after transplantation. Experiment II: In a 60-min warm ischemia model, grafts were evaluated 2 hr after transplantation (6 rats/group), and survival was assessed (7 rats/group).

RESULTS

Experiment I: Group-VSOP-NO had lower alanine aminotransferase (ALT) (P<0.001), hyaluronic acid (P<0.05), and malondialdehyde (MDA) (P<0.001), hepatic interleukin-6 expression (IL-6) (P<0.05), and hepatic tumor necrosis factor-alpha (TNF-α) expression (P<0.001). Hepatic eNOS expression (P<0.001) was upregulated, whereas hepatic iNOS (P<0.01) and ET-1 (P<0.001) expressions were downregulated. The damage of hepatocyte and sinusoidal endothelial cells (SECs) were lower in group-VSOP-NO.Experiment II: VSOP-NO decreased ET-1 and 8-hydroxy-2'deoxyguanosine (8-OHdG) expression and improved survival after transplantation by 71.4% (P<0.01).

CONCLUSION

These results suggest that VSOP-NO effectively reconditions warm ischemia-damaged grafts, presumably by decreasing ET-1 upregulation and oxidative damage.

A novel organ preservation for small partial liver transplantations in rats: venous systemic oxygen persufflation with nitric oxide gas

The prognosis for recipients of small liver grafts is poor. The aim of this study was to determine the impact of venous systemic oxygen persufflation (VSOP) with nitric oxide (NO) gas for 30% partial liver preservation and transplantation in rats. After we determined optimal NO concentration as 40 ppm in vitro with the isolated perfused rat liver model, we assessed liver injury and regeneration in vivo at 1, 3, 24 and 168 h after transplantation in the following three groups after 3 h-cold storage (n = 20 per group): control group = static storage; VSOP group = oxygen persufflation and VSOP+NO group = oxygen with NO persufflation. The liver graft persufflation was achieved with medical gas via the suprahepatic vena cava; In comparison with control group after transplantation, VSOP+NO preservation (1) increased portal circulation, (2) reduced AST and ALT release, (3) upregulated hepatic endothelial NO synthase, (4) reduced hepatocyte and bileductule damage and (5) improved liver regeneration. These results suggest that gaseous oxygen with NO persufflation is a novel and safe preservation method for small partial liver grafts, not only alleviating graft injury but also improve liver regeneration after transplantation.

Persufflation (or gaseous oxygen perfusion) as a method of organ preservation

Improved preservation techniques have the potential to improve transplant outcomes by better maintaining donor organ quality and by making more organs available for allotransplantation. Persufflation, (PSF, gaseous oxygen perfusion) is potentially one such technique that has been studied for over a century in a variety of tissues, but has yet to gain wide acceptance for a number of reasons. A principal barrier is the perception that ex vivo PSF will cause in vivo embolization post-transplant. This review summarizes the extensive published work on heart, liver, kidney, small intestine and pancreas PSF, discusses the differences between anterograde and retrograde PSF, and between PSF and other conventional methods of organ preservation (static cold storage, hypothermic machine perfusion). Prospective implications of PSF within the broader field of organ transplantation, and in the specific application with pancreatic islet isolation and transplant are also discussed. Finally, key issues that need to be addressed before PSF becomes a more widely utilized preservation strategy are summarized and discussed.

Hypothermic reconditioning by gaseous oxygen persufflation after cold storage of porcine kidneys

BACKGROUND

Delayed graft function still represents a major complication in clinical kidney transplantation. Here we tested the possibility to improve functional outcome of cold stored kidneys a posteriori by hypothermic reconditioning using retrograde oxygen persufflation (ROP) immediately prior to reperfusion.

METHODS

Kidneys from female German Landrace pigs were flushed with Histidine-Tryptophan-Ketoglutarate (HTK) solution and cold-stored for 18 h (control). Some grafts were subsequently subjected to 90 min of retrograde oxygen persufflation (ROP) via the renal vein during cold preservation. Early graft function of all kidneys was assessed thereafter by warm reperfusion in vitro (n=6, resp.).

RESULTS

Renal function upon reperfusion was significantly enhanced by ROP with an approximately twofold increase in renal clearances of creatinine and urea. ROP also led to higher renal vascular flow rates, enhanced urine output and mitigated histological alterations.

CONCLUSION

It is concluded that initial graft function can be improved by 90 min of hypothermic gaseous oxygenation after arrival of the preserved organ in the transplantation clinic.

Liver transplantation using Donation after Cardiac Death donors

The success of solid organ transplantation has brought about burgeoning waiting lists with insufficient donation rates and substantial waiting list mortality. All countries have strived to expand donor numbers beyond the standard Donation after Brain Death (DBD). This has lead to the utilization of Donation after Cardiac Death (DCD) donors, also frequently referred to as Non-Heart Beating Donors (NHBD). Organs from these donors inevitably sustain warm ischaemic damage which varies in its extent and affects early graft function as well as graft survival. As a consequence, 'non-vital' organs such as renal transplants have increased rapidly from DCD donors but more 'vital' organ transplants such as the liver have lagged behind. However, an increasing proportion of liver transplants are now derived from DCD donors. This article covers this expansion, current results, pitfalls, and steps taken to minimize complications and to improve outcome, and future developments that are likely to occur.

Oxygen persufflation as adjunct in liver preservation (OPAL): study protocol for a randomized controlled trial

BACKGROUND

Early graft dysfunction due to preservation/reperfusion injury represents a dramatic event after liver transplantation. Enhancement of donor organ criteria, in order to cope with the ever increasing donor shortage, further increases graft susceptibility to ischemic alterations. Major parts of post-preservation injury, however, occur at the time of warm reperfusion but not during ischemic storage; successful reperfusion of ischemic tissue in turn depends on an adequate redox and intracellular signal homeostasis. The latter has been shown experimentally to be favorably influenced by oxygen persufflation within short time spans. Thus viability of marginally preserved liver grafts could still be augmented by transient hypothermic reconditioning even after normal procurement and static cold storage. The present study is aimed to confirm the conceptual expectations, that hypothermic reconditioning by gaseous oxygen persufflation is a useful method to suppress injurious cellular activation cascades and to improve post-ischemic recovery of marginally preserved liver grafts.

METHODS/DESIGN

OPAL is a prospective single center randomized proof of concept study, including two parallel groups in a total of 116 liver transplant patients. The effect of an in hospital treatment of the isolated liver graft by 2 hours of oxygen persufflation immediately prior to transplantation will be assesses as compared to standard procedure (cold storage without further intervention). The primary endpoint is the peak transaminase serum level (AST) during the first three days after transplantation as a surrogate readout for parenchymal liver injury. Other outcomes comprise patient and graft survival, time of intensive care requirement, hepatic tissue perfusion 1h after revascularisation, early onset of graft dysfunction based on coagulation parameters, as well as the use of a refined scoring-system for initial graft function based on a multi-parameter (AST, ALT, Quick and bilirubin) score. Furthermore, the effect of OPAL on molecular pathways of autophagy and inflammatory cell activation will be evaluated. Final analysis will be based on all participants as randomized (intention to treat).

TRIAL REGISTRATION

Current Controlled Trials ISRCTN00167887.

Gaseous persufflation with carbon monoxide during ischemia protects the isolated liver and enhances energetic recovery

BACKGROUND

The benefit of carbon monoxide as applied by controlled, continuous gaseous persufflation during liver preservation on postischemic graft recovery was investigated in an isolated rat liver model.

METHODS

Livers from male Wistar rats were retrieved 30 min after cardiac arrest of the donor and subjected to 18 h of cold storage. Some grafts were subjected to gaseous persufflation with carbon monoxide (CO, dissolved in nitrogen) during static cold storage at a concentration of 50 ppm or 250 ppm. Graft viability was assessed thereafter upon warm reperfusion in vitro.

RESULTS

CO-persufflation significantly reduced cellular enzyme loss (maximal at 50 ppm) and functional recovery (bile production and energy charge) upon reperfusion by about 50%. The effect was associated with a reduction of free radical-induced lipid peroxidation, lower vascular perfusion resistance, and improved mitochondrial ultrastructure.

CONCLUSION

Viability of cold stored liver grafts can be notably augmented by gaseous ex vivo application of low dose CO to the isolated organ.

Dopamine as additive to cold preservation solution improves postischemic integrity of the liver

Dopamine pretreatment has been used to confer protection against cellular injury following hypothermia or anoxia, especially in vascular endothelial cells. Ischemia/reperfusion-associated tissue alterations still represent a major drawback in liver transplantation. The present study was aimed to investigate the effect of dopamine as an ex vivo adjunct, added to the cold storage solution, on cold preservation of the liver. Rat livers were excised 30 min after cardiac arrest, flushed with preservation solution and cold stored for 18 h. Dopamine (10, 50 or 100 microM) was added to the preservation solution in other livers. Organ viability was evaluated by 120 min of warm reperfusion in vitro (n = 6, resp.). Dopamine induced a dose related up to fourfold (at 50 mum) reduction in parenchymal (ALT, LDH) and mitochondrial (GLDH) enzyme release and significantly reduced histologic signs of tissue injury. Bile production and tissue ATP was doubled by dopamine. On the molecular level, dopamine enhanced postischemic phosphorylation of protein kinase A and p42/44 MAP kinase. Inhibition of cAMP-PKA pathway by simultaneous application of RP-cAMPs had no effect on P42/44 phosphorylation, or functional recovery of dopamine-treated grafts. Dopamine supplementation of the flush-out solution appears as a simple way for ex vivo augmentation of liver viability during preservation, not mediated via the catecholamine-cAMP signal cascade.

Normothermic versus hypothermic ex vivo flush using a novel phosphate-free preservation solution (AQIX) in porcine kidneys

BACKGROUND

The initial flush of an organ is important to remove any cellular components from the microcirculation before storage. The aim of this study was to assess graft function after an ex vivo warm flush with a novel non-phosphate buffered preservation solution AQIX RS-I (AQIX) compared with a traditional cold flush.

METHODS

Porcine kidneys were either warm-flushed with AQIX RS-I at 30°C, or cold-flushed at 4°C with University of Wisconsin solution (UW) or hyperosmolar citrate (HOC) preservation solution at a pressure of 100 cmH2O (n = 6). Renal function was measured ex vivo by perfusing the organs with autologous blood at 37°C on an isolated organ perfusion system.

RESULTS

The AQIX group flushed significantly quicker than the cold stored groups (22 ± 1.8 versus UW 4.9 ± 1.6 versus HOC 10 ± 1.6 mL/min/100g; P = 0.001) and gained less weight than the UW group (19 ± 2.9 versus UW 30 ± 3.4 versus HOC 21% ± 7.7%; P = 0.025). The AQIX group also had superior acid-base homeostasis. Functional results, histologic analysis, and ADP: ATP levels were comparable between the groups.

CONCLUSION

Flushing kidneys with AQIX at 30°C cleared the renal microcirculation of blood more rapidly without any detrimental effects when compared to traditional cold flushing with UW or HOC at 4°C. Warm initial flushing has potential to be developed as part of normothermic renal preservation techniques.

Protective effect of reduced glutathione and venous systemic oxygen persufflation on rat steatotic graft following liver transplantation

BACKGROUND

The aim of this study is to explore the protective effect of high-dose reduced glutathione (GSH) preconditioning and venous systemic oxygen persufflation (VSOP) on rat steatotic liver grafts following transplantation.

METHODS

Steatotic liver model was established by feeding rats a high-fat, high-cholesterol diet, and infusing stomach with 50% alcohol (1 mL/100g body weight/d) for 6 wk. In the pretreated group, short-term and high-dose of GSH administration and VSOP were performed. In rat orthotopic liver transplantation model, the recipient survival, liver function, hepatic microcirculation blood flow, hepatic redox, hepatocytes apoptosis and necrosis, and hepatic ultrastructure alteration were observed.

RESULTS

In the pretreated rat steatotic grafts, hepatic GSH (from 29.43 +/- 4.83 to 41.56 +/- 8.51mg/mgprot), superoxide dismutase (SOD) (from 48.32 +/- 6.27 to 67.74 +/- 7.68 NU/mgprot), and adenosine triphosphate (ATP) (from 1.61 +/- 0.20 to 2.28 +/- 0.09 micromoles/g) were significantly increased (P < 0.05), whereas malondialdehyde (MDA) was significantly decreased (from 7.20 +/- 2.18 to 4.63 +/- 0.58 nmol/mgprot, P < 0.05). The hepatocyte necrosis of fatty liver graft was significantly reduced in the pretreated group when compared with non-treated fatty ones (37.71% +/- 9.69% versus 16.63% +/- 5.53%; t = 3.777, P = 0.014), and significantly improved liver function and hepatic ultrastructure were observed in the pretreated fatty liver group after operation. The animal survival after transplanted with fatty liver was significantly improved (chi(2) = 4.07, P = 0.0436).

CONCLUSION

A short course pretreatment with high-dose GSH and oxygen persufflation during cold preservation effectively protect steatotic liver grafts from ischemic damage and significantly improve early survival rate in a rat fatty liver transplantation model.

Function and quality of kidneys after cold storage, machine perfusion, or retrograde oxygen persufflation: results from a porcine autotransplantation model

OBJECTIVES

Especially for preservation of marginal donor organs, machine perfusion (MP) and retrograde oxygen persufflation (ROP) are alternatives to cold storage (CS). Using a porcine kidney autotransplantation model we compared metabolic and morphologic effects of CS, ROP, and MP on kidneys exposed to warm ischemia.

METHODS

Kidneys of 21 pigs were exposed in situ to warm ischemia for 60min. The kidneys were randomly allocated to three experimental groups, each receiving a 4-h treatment of either cold storage, machine perfusion, or retrograde oxygen persufflation. Tissue samples were examined for malondialdehyde and histological changes. Daily blood samples were examined for creatinine levels.

RESULTS

Seven days after transplantation, the plasma creatinine levels in the CS and MP groups were still significantly elevated above the baseline values. In the ROP group, all animals exhibited nearly normal creatinine levels. Malondialdehyde, an indicator of lipidperoxidation, was dramatically increased in the machine perfused kidneys on day 7, whereas the malondialdehyde levels in the other two groups were near normal values. The MP kidneys exhibited the most striking histological changes.

CONCLUSION

Though MP has been well introduced in organ transplantation, in our opinion, it must still be optimized and standardized. It is necessary to clarify questions such as whether there is a need for oxygenation during perfusion, the length of perfusion, the impact of pressure, and the effects of additional scavengers. The results of the present study suggest the reconsideration of the ROP-technique for the preservation of predamaged donor grafts especially of NHBD and further studies, comparing MP and ROP upon long term preservation are strongly encouraged.

Possibility of conditioning predamaged grafts after cold storage: influences of oxygen and nutritive stimulation

The potential of short-term oxygenated perfusion after cold storage (CS) to reverse deleterious priming of nonheart beating donors grafts should be investigated, addressing the respective role of oxygenation and nutrients or metabolic charge. Livers were retrieved 30 min after cardiac arrest of male Wistar rats and preserved with histidine tryptophan ketoglutarate (HTK)-solution for 18 h by CS. After 16 h, some livers were put on an oxygenated machine-preservation-circuit for the last 2 h and conditioned by cold perfusion with either HTK (conHTK), HTK supplemented with adenosine, phosphate and glucose (conHTK+) or Williams-E solution (conWE). Upon warm reperfusion, postconditioning with any of the solutions led to a significant (three- to fivefold) reduction of parenchymal damage (ALT, GLDH-release) compared with CS. Metabolic recovery (bile production) was also significantly enhanced compared with CS, with best results found after conHTK. The beneficial effect of postconditioning with HTK was associated with a significantly mitigated cleavage of caspase 12 and 3. We conclude from these data that conditioning of predamaged livers is possible even after CS by short-term oxygenated perfusion in the cold and, under these conditions, not depending on energetic support or nutritive stimulation.

Primary organ function of warm ischaemically damaged porcine kidneys after retrograde oxygen persufflation*

BACKGROUND

As warm ischaemic damage is a major reason for the loss of donor organs, an experimental study was performed in order to evaluate retrograde oxygen persufflation (ROP) as a method to extend the warm ischaemic tolerance of kidneys.

METHODS

Kidneys of 32 pigs were exposed to warm ischaemia for 60, 90 or 120 min. Then, 16 kidneys were subjected to ROP for 4 h at 4 degrees C and 16 controls were stored in cold UW-solution, followed by autotransplantation.

RESULTS

Only in the group with 60 min warm ischaemic time and ROP did all animals survive the observation period of 7 days. In all other groups some animals died due to anuria. Short-term survivors in these groups had significantly higher creatinine levels.

CONCLUSIONS

In this setting, ROP was superior to cold storage when applied after 60 min of warm ischaemia. Clinical evaluation of ROP in the setting of marginal donors and non-heartbeating donation is recommended.

Preharvest donor hyperoxia predicts good early graft function and longer graft survival after liver transplantation

A total of 44 donor/recipient perioperative and intraoperative variables were prospectively analyzed in 89 deceased-donor liver transplantations classified as initial good graft function (IGGF) or initial poor graft function (IPGF) according to a scoring system based on values obtained during the 1st 72 postoperative hours from the serum alanine aminotransferase (ALT) concentration, bile output, and prothrombin activity. The IGGF compared with the IPGF group showed: 1) longer graft (P = .002) and patient (P = .0004) survival; 2) at univariate analysis, a higher (mean [95% confidence interval]) preharvest donor arterial partial pressure of oxygen (PaO(2)) (152 [136-168] and 104 [91-118] mmHg, respectively; P = .0008) and arterial hemoglobin oxygen saturation (97.9 [97.2-98.7] and 96.7 [95.4-98.0]%, respectively; P = .0096), a lower percentage of donors older than 65 years (13 and 33%, respectively; P = .024), a lower percentage of donors treated with noradrenaline (16 and 41%, respectively; P = .012). At multivariate analysis, IGGF was associated positively with donor PaO(2) and negatively with donor age greater than 65 years and with donor treatment with noradrenaline. Independently from the grouping according to initial graft function, graft survival was longer when donor PaO(2) was >150 mmHg than when donor PaO(2) was < or =150 mmHg (P = .045). In conclusion, preharvest donor hyperoxia predicts IGGF and longer graft survival.

Role of hepatocytes and bile duct cells in preservation-reperfusion injury of liver grafts

In liver transplantation, it is currently hypothesized that nonparenchymal cell damage and/or activation is the major cause of preservation-related graft injury. Because parenchymal cells (hepatocytes) appear morphologically well preserved even after extended cold preservation, their injury after warm reperfusion is ascribed to the consequences of nonparenchymal cell damage and/or activation. However, accumulating evidence over the past decade indicated that the current hypothesis cannot fully explain preservation-related liver graft injury. We review data obtained in animal and human liver transplantation and isolated perfused animal livers, as well as isolated cell models to highlight growing evidence of the importance of hepatocyte disturbances in the pathogenesis of normal and fatty graft injury. Particular attention is given to preservation time-dependent decreases in high-energy adenine nucleotide levels in liver cells, a circumstance that (1) sensitizes hepatocytes to various stimuli and insults, (2) correlates well with graft function after liver transplantation, and (3) may also underlie the preservation time-dependent increase in endothelial cell damage. We also review damage to bile duct cells, which is increasingly being recognized as important in the long-lasting phase of reperfusion injury. The role of hydrophobic bile salts in that context is particularly assessed. Finally, a number of avenues aimed at preserving hepatocyte and bile duct cell integrity are discussed in the context of liver transplantation therapy as a complement to reducing nonparenchymal cell damage and/or activation.

Extension of ischemic tolerance of porcine livers by cold preservation including postconditioning with gaseous oxygen

BACKGROUND

Transplantation of organs from nonheartbeating donors was recommended to reduce organ shortage. In vitro experiments with rat livers have shown that the warm ischemic tolerance of the liver may be extended by persufflation with gaseous oxygen during cold storage. The qualification of this method for procurement of livers harvested after cardiac arrest was tested in an in vivo approach with pigs.

METHODS

Livers from 15 donor pigs were explanted, heparinized, flushed with and stored in University of Wisconsin solution for 4 hr at 4 degrees C, and then implanted into 15 recipients. The organs were dissected immediately after cardiac arrest (group 1) or after 60 min of warm ischemia (groups 2 and 3). Group 2 livers received 75,000 IU of superoxide dismutase together with the flush solution and were persufflated with gaseous oxygen via the venous vascular system during cold storage. Main end point was survival after 5 days. Additionally, metabolic, functional and inflammatory criteria were measured in the blood.

RESULTS

All animals of the groups 1 and 2 survived, all animals of group 3 died within 3 hr after reperfusion. In all groups the blood parameters reflected significant damage of the livers. However, the ischemic damage was comparable in the groups 1 and 2 whereas the livers of group 3 exhibited significantly higher levels of aspartate alanine aminotransferase and lactate dehydrogenase, and a significantly elongated partial thromboplastin time 1 hr after reperfusion (P=0.016).

CONCLUSIONS

Venous systemic oxygen persufflation in combination with antioxidative medication is a promising new method of resuscitating ischemically altered livers from nonheartbeating donors for successful transplantation.

Cold preservation of fatty liver grafts: prevention of functional and ultrastructural impairments by venous oxygen persufflation

BACKGROUND/AIMS

The incidence of steatosis in livers retrieved for organ transplantation is up to 30%. Due to the shortage of donor organs, many of these livers are accepted for clinical transplantation, although a high rate of graft dysfunction is associated with ischemic preservation of steatotic livers. The present study was intended to reduce the ischemia/reperfusion injury of steatotic grafts by the use of venous systemic oxygen persufflation during cold storage.

METHODS

A histologically-documented mild to moderate steatosis was induced in livers of Wistar rats by fasting for 2 days and subsequent feeding of a fat-free diet enriched in carbohydrates. Fatty livers were retrieved and flushed via the portal vein with 60 ml of HTK. In group A, livers were then stored ischemically at 4 degrees C for 24 h. Livers of group B were additionally connected to a gaseous oxygen supply and persufflated with O2 via the venous vascular system during the cold storage period. Viability of the livers was then assessed upon isolated perfusion in vitro with oxygenated Krebs-Henseleit buffer.

RESULTS

Venous systemic oxygen sufflation resulted in a relevant and significant reduction of parenchymal (ALT: 132+/-90 vs 434+/-172 U/l; p<0.01) and mitochondrial (GLDH: 116+/-57 vs 633+/-241 U/l; p<0.001) enzyme release during reperfusion. Moreover, Kupffer cell activation, as evaluated from acid phosphatase activity in the perfusate, was reduced to about 1/3 (4.0+/-1.3 vs 11.9+/-5.3 U/l; p<0.01). Electron microscopic analysis revealed that the liver mitochondria and sinusoidal endothelial lining were better preserved after oxygen persufflation, which was in line with the data on enzyme release and the increased portal perfusion pressure in the untreated group, while normal values were found after venous systemic oxygen sufflation.

CONCLUSION

Venous oxygen persufflation may thus represent a useful tool for the safe and improved preservation of ischemia-sensitive steatotic livers.

Excellent recovery after prolonged heart storage by preservation with coronary oxygen persufflation: orthotopic pig heart transplantations after 14-hr storage

BACKGROUND

Improvement of heart preservation is still the greatest challenge in preservation research. The unchanged severe restriction of acceptable storage periods of heart grafts since the beginning of clinical heart transplantation indicates that technical innovations are necessary if a substantial improvement is to be achieved.

METHODS

Here, we present the results of hypothermic preservation using the innovative technique of coronary oxygen persufflation (COP). COP simply adds gaseous oxygen to hypothermic graft storage and requires only a "valve guard" for reversible closure of the aortic valve. Fourteen-hr preservation was followed by orthotopic transplantation and evaluations of functional as well as metabolic recovery. Mature pig hearts, a model with restricted preservation tolerance similar to the human heart, were used to guarantee the clinical relevance of this study.

RESULTS

After 14-hr hypothermic storage, COP-preserved hearts were able to recover within 2 hr of cardiopulmonary bypass to a steady cardiovascular function without mechanical or pharmacologic support. The left ventricular pressure amplitude of mHTK-COP-preserved hearts as well as energy charge potential recovered to pregrafting values and the ventricular power output to 66%. Hearts simply stored in University of Wisconsin (UW), modified Bretschneider's histidine-tryptophan-ketoglurate (mHTK), or Euro-Flush with glutathione (EFG) solution had only limited recovery, with significantly lower ventricular power output of 18%, 29% or 30% of pregrafting controls on average.

CONCLUSIONS

Fourteen-hr oxygenated pig heart preservation using COP results in optimal recovery. Storage preservation in solutions containing hyaluronidase (mHTK and EFG) results in higher recoveries as compared to UW solution, an effect that may support the excellent recovery after mHTK-COP preservation.

Microscopic analysis of NADH fluorescence during aerobic and anaerobic liver preservation conditions: A noninvasive technique for assessment of hepatic metabolism

Gaseous insufflation of oxygen via the venous vascular system is thought to be an useful tool for preventing anoxic tissue injury during extended time periods of ischemic preservation and for allowing for an improved recovery of organ function after transplantation. The present study aimed at the application of a noninvasive technique for monitoring effectiveness and homogeneity of gaseous areation by using an epiillumination microscopic technique for assessment of tissue nicotinamide adenine dinucleotide (NADH) fluorescence. Rat livers were flushed with and stored in University of Wisconsin solution at 4 degrees C for 48 h (n = 20). In half of the experiments (n = 10) gaseous oxygen was applied subsequent to organ harvest. Using ultraviolet-excitation high-resolution microscopy and computer-assisted image analysis liver surfaces were scanned for NADH intensity and spatial heterogeneity at 1, 24, and 48 h preservation time. Livers simply stored without aeration served as controls (n = 10). NADH intensity data were compared with corresponding data of tissue adenosine triphosphate (ATP) concentrations determined enzymatically. NADH fluorescence already differed at 1 h preservation between the two groups with significantly lower values in the aerobically stored livers. NADH fluorescence further decreased between 1 and 24 h preservation and remained low until 48 h, whereas in the anaerobically stored livers NADH fluorescence was found to be constantly high over the entire observation period. Aerobic storage resulted in rather homogeneous tissue oxygenation with an intrahepatic variation of NADH fluorescence <20%. In parallel, oxygen persufflation appropriately restored tissue ATP content within 1 to 24 h of preservation, while the simply stored livers exhibited pronounced depletion of ATP. We demonstrate for the first time that by means of retrograde gaseous oxygenation, ischemic livers can be readily and effectively oxygenated. Our study further indicates that the noninvasive microscopic analysis of tissue NADH fluorescence may be an useful tool for estimating efficiency of strategies in organ preservation.

Biophysical aspects of liver aeration by vascular persufflation with gaseous oxygen

BACKGROUND

Venous systemic oxygen persufflation of the liver (i.e., gaseous insufflation of oxygen via the venous vascular system) has proven to be an effective tool for preventing anoxic tissue injury during extended time periods of ischemic preservation. It also allows for an improved recovery of the persufflated organ after orthotopic transplantation.

METHODS

Biophysical aspects of the persufflation technique with regard to persufflation pressure (9 mmHg versus 18 mmHg) and oxygen concentration (pure oxygen versus air) in the persufflation gas were investigated in rat livers, using epi-illumination microscopic detection of autofluorescence of NADH, which accumulates in anoxic tissue.

RESULTS

We demonstrated that a low-pressure persufflation (9 mmHg) is as sufficient as a higher pressure persufflation (18 mmHg) in oxygenating the ischemic organ. Moreover, oxygenation of the liver was found to be complete and rather homogeneous upon the pure oxygen persufflation, irrespective of the insufflation pressure used. In contrast, insufflation of air instead of pure oxygen resulted in insufficient aeration of the liver, even at the higher persufflation pressure of 18 mmHg.

CONCLUSIONS

Our results indicate that the oxygen concentration of the persufflation gas rather than the persufflation pressure is a determinant of successful tissue oxygenation during cold storage.