Influence of flow and addition of oxygen during porcine liver hypothermic machine perfusion

INTRODUCTION: In contrast with kidneys, data on hypothermic machine perfusion (HMP) of livers remain scarce. Optimal liver HMP is poorly defined. Superiority of liver HMP over simple cold storage (SCS), the current standard preservation, must be proven before HMP is applied clinically. In this study, morphology and adenosine triphosphate (ATP) contents of HMP livers at different flows and with versus without O(2) studied in a porcine ex vivo model were compared to SCS. METHODS: Pig livers were procured, flushed with HTK and preserved via SCS or HMP at 3 HMP settings: high flow (HF); low flow (LF); low flow + O(2) (300 mm Hg) (LFO). HMP livers were perfused via the hepatic artery (HA) and portal vein (PV) with KPS-1 TM at 4 degrees C to 6 degrees C for 24 hours with HF: PV: 3 to 5 mm Hg, 1 mL/g liver/min for HA and 25 mm Hg; LF: PV: 3 to 5 mm Hg, 0.5 ml/g liver/min with HA: 20 mm Hg. Morphology and ATP levels were measured in preserved liver tissues. RESULTS: Throughout the SCS preservation, livers remained intact. In HMP livers, vacuoles appeared after 4 hours of preservation in the HF group and after 12 hours in the LF livers. LFO livers remained intact with limited vacuoles. Compared to SCS, HMP livers showed dilated sinusoids, particularly in the HF group. ATP remained relatively constant or even increased during HMP, particularly in the LF group, whereas ATP decreased after SCS. CONCLUSION: Among the various HMP settings, HMP with LFO was superior. ATP levels were the highest in LF. In contrast with all HMP groups, SCS showed the lowest ATP levels, indicating that HMP has the potential to better preserve energy stores.     

Hypothermic machine perfusion of the liver and the critical balance between perfusion pressures and endothelial injury

Hypothermic machine perfusion (HMP) provides better protection against cold ischemic injury than cold storage in marginal donor kidneys. Also, in liver transplantation a switch from static cold storage to HMP could be beneficial as it would allow longer preservation times and the use of marginal donors. A critical question concerning application of HMP in liver preservation is the crucial balance between perfusion pressure and occurrence of endothelial injury. Rat livers were cold-perfused for 24 hours to study perfusion pressures for both hepatic artery and portal vein. Cold storage served as control and was compared to HMP-preserved livers using a mean arterial perfusion pressure of 25 mm Hg and a portal perfusion pressure of 4 mm Hg (25% of normothermic liver circulation) and to HMP at 50 mm Hg and 8 mm Hg perfusion, respectively (50% of normothermic liver circulation). UW solution was enriched with 14.9 micromol/L propidium iodide (PI) to stain for dead cells and with an additional 13.5 micromol/L acridine orange to stain for viable hepatocytes. A low PI-positive cell count was found using HMP at 25% of normal circulation compared to cold storage. The PI count was high for the HMP group perfused at just 50% of normal circulation compared to HMP at 25% and compared to cold storage. In summary, for liver HMP, perfusion at 25% showed complete perfusion with minimal cellular injury. HMP using perfusion pressures of 25 mm Hg for the hepatic artery and 4 mm Hg for the portal vein is feasible without induction of endothelial injury.     

Pronlonged hypothermic machine perfusion preserves hepatocellular function but potentiates endothelial cell dysfunction in rat livers

BACKGROUND: Although hypothermic machine perfusion (HMP) preservation has been shown to improve organ function and to expand the organ donor pool, problems still exist with the current HMP technology for liver preservation. The present study was conducted to investigate endothelial and hepatocellular functions following extended HMP (> r =24 hr) in rat liver model. METHODS: Following 24-hour hypothermic HMP with University of Wisconsin (UW) solution or 24-hour simple cold storage (SCS), livers were reperfused with Krebs-Henseleit buffer solution at 37 degree C for 30 minutes. Hepatocyte damage and function were assessed by measuring lactate dehydrogenase (LDH) activity, bile production, and indocyanine green (ICG) extraction. Sinusoidal endothelial cell (SEC) function and permeability were determined by hyaluronic acid (HA) uptake and multiple indicator dilution (MID) method, respectively. RESULTS: After 24-hour hypothermic preservation, HMP livers showed lower released LDH levels, higher bile flow rate, and greater hepatic ICG uptake compared with SCS livers. However, LDH levels became significantly higher in HMP than in SCS after 30 minutes of warm perfusion. The increased enzyme levels were accompanied by a significant increase in endothelial permeability to albumin and a decrease in hyaluronic acid uptake in HMP compared to SCS. Liver wet/dry weight ratio confirmed a greater edema in HMP livers than SCS livers. CONCLUSION: These results suggest that 24-hour hypothermic HMP may help preservation of hepatocyte function, but endothelial cell dysfunction during the cold preservation may play a key role in hepatocyte dysfunction and parenchymal cell death upon reperfusion.     

Hypothermic machine perfusion of rat livers preserves endothelial cell function

This study was conducted to investigate the effect of starch in the preservation solution during hypothermic machine perfusion (HMP) on endothelial cell and hepatocyte functions in an isolated perfused rat liver model. Livers isolated from male Sprague-Dawley rats were perfused with the University of Wisconsin (UW) solution (HMP + starch group); modified UW solution (starch omitted) (HMP - starch group) at 0.4 mL/min per g liver; or simply stored in the UW solution (SCS group) at 4 degrees C for 24 hours. Following preservation, livers from HMP + starch, HMP - starch, SCS, and control group (without preservation) were perfused with Krebs-Henseleit Buffer solution at 37 degrees C for 30 minutes. Samples were taken every 10 minutes during 30-minute warm perfusion to assess hepatocyte and endothelial cell function and damage. After 24 hours of hypothermic preservation and 30 minutes rewarming, livers in the HMP + starch group displayed significantly lower lactate dehydrogenase levels and higher bile production. Endothelial cell function was also improved as indicated by hyaluronic acid uptake and shorter transient time for albumin observed in a multiple indicator dilution study. Liver wet and dry ratio and histological findings confirmed reduced edema formation in the tissue of the HMP + starch group livers compared with that of the HMP - starch and SCS group livers. These results suggest that HMP with the UW solution containing starch improve endothelial cell function and induce less hepatocellular damage following 24-hour preservation compared to SCS and HMP with the starch-free UW solution. These results also suggest that oncotic support may be an important component in preserving hepatic microcirculation in HMP.     

Hypothermic machine perfusion of the liver: is it more complex than for the kidney?

Background

Hypothermic machine perfusion (HMP) is superior to simple cold storage (SCS) for the preservation of kidney grafts. Whether HMP is superior to SCS for liver preservation is not known. Before a HMP system can be used clinically for the liver, its superiority to SCS needs to be demonstrated in an in vivo large animal transplant model.

Objective

The aim was to compare outcomes after liver transplantation (LT) following preservation by SCS or HMP using technology/perfusion conditions similar to those for kidney HMP.

Methods

Pig livers were perfused via the hepatic artery and portal vein for 4 hours with nonoxygenated 4°C University of Wisconsin machine perfusion solution. In the SCS group, flushed livers were stored in histidine-tryptophan-ketoglutarate solution. After preservation by SCS (n = 6) or HMP (n = 8) and LT, we assessed graft and recipient survivals, pH and lactate, hepatocellular damage [aspartate aminotransferase (AST)], Kupffer cell activation (β-galactosidase), tumor necrosis factor (TNF) α production, endothelial cell function (hyaluronic acid), and expression of Krüppel-like factor (KLF) 2 and 4, which are mediators of the flow-dependent vasoprotective endothelial phenotype.

Results

No primary graft nonfunction was observed; livers recovered equally well from the postanhepatic metabolic acidosis in both groups. Pig survival was 5/6 (83%) in the SCS versus 2/8 (12.5%) in the HMP group (P = .04). Livers from both groups recovered equally well from the postanhepatic metabolic acidosis. AST in liver rinse-out samples obtained before LT were lower in the HMP than in the SCS group (P < .05). After reperfusion, AST and β-galactosidase were equally increased in both groups (P = .13 and 0.962, respectively); TNF-α and hyaluronic acid levels were higher after HMP versus SCS (P = .001 and 0.043, respectively). KLF-2 and -4 expressions were equally up-regulated after reperfusion in the SCS and HMP groups.

Conclusions

In this in vivo model, liver HMP with subsequent transplantation was feasible. However, we did not demonstrate an advantage of HMP, using perfusion conditions shown to be effective for the kidney, over SCS. Despite similar immediate graft function, TNF-α generation, and endothelial cell dysfunction were more pronounced after HMP.     

Attempt to rescue discarded human liver grafts by end ischemic hypothermic oxygenated machine perfusion

In a porcine liver transplant model, a brief period of oxygenated hypothermic machine perfusion (HMP) at the end of simple cold storage (SCS) has been shown to improve the viability of damaged liver grafts. To test the clinical validity of this strategy, we randomized SCS-discarded human liver grafts to either 4 hours of HMP (n = 13) or an additional 4 hours of SCS (n = 14). All livers were then warm reperfused to mimic ischemia-reperfusion injury ex vivo. The settings for HMP were: portal vein: 3 mm Hg, 300 mL/min and hepatic artery: 20 mm Hg, po₂: 300 mm Hg. Perfusion used Kidney Machine Perfusion Solution at 4°C to 8°C. During warm reperfusion, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) values were higher (P < .015) among the SCS versus HMP methods at all times. The AST slope was lower in HMP versus SCS (P = .01). The LDH slope tended to be lower for HMP versus SCS (P = .07). Morphological scores were not different between HMP and SCS. At the start of warm reperfusion, MAPK was lower in HMP versus SCS (P = .02). Endothelin-1 (EDN1) and ICAM-1 tended to be lower in HMP versus SCS (P = .1 and .07, respectively). No difference was noted in MAPK, EDN1, and ICAM-1 after 60 or 120 minutes of warm reperfusion. In conclusion, HMP down-regulated MAPK and tended to reduce EDN1 and ICAM-1 mRNA in human liver grafts. During warm reperfusion, HMP versus SCS livers showed reduced AST and LDH release but no morphological difference. Further optimization of liver HMP may require different timing/duration of perfusion and/or an higher perfusion temperature.     

Hepatic function in hypothermically stored porcine livers: comparison of hypothermic machine perfusion vs cold storage

Hypothermic machine perfusion (HMP) has a potential to relieve the current donor liver crisis by providing an improved and extended preservation method. This study examined the effect of HMP on hepatocellular functions, using a prototype liver transporter capable of preserving livers for 24 hours. Livers obtained from adult farm pigs (28 to 32 kg body weight) were divided into three groups: fresh control, HMP, and simple cold storage (n = 4 each). A 4-hour normothermic reperfusion of livers was conducted to assess hepato-metabolic and cellular functions. The hepatic transport function, as indicated by canalicular excretion of indocyanine green, was improved in the HMP group than in the SCS group. The overall tissue viability, as indicated by oxygen consumption levels, was notably improved in HMP and control livers as compared to the SCS group. Higher bile production in both the preserved groups as compared to the fresh control livers could be a result of biliary edema and leakage of plasma into the canaliculus. The hepato-cellular injury, measured by ALT, release was significantly greater in the SCS group as compared to the HMP and control groups. These findings suggest that HMP could be a better method to preserve hepatic function and overall tissue viability as compared to SCS. Improved hepatic functions are indirect indicators of superior microcirculation and sinusoidal endothelial cell functions. Further studies in progress will evaluate these functions to confirm the significance of these observations.     

Improved preservation of warm ischemic livers by hypothermic machine perfusion with supplemented University of Wisconsin solution.

Hypothermic machine perfusion (HMP) has the potential to improve recovery and preservation of Donation after Cardiac Death (DCD) livers, including uncontrolled DCD livers. However, current perfusion solutions lack the needed substrates to improve energy recovery and minimize hepatic injury, if warm ischemic time (WIT) is extended. This proof-of-concept study tested the hypothesis that the University of Wisconsin (UW) solution supplemented with anaplerotic substrates, calcium chloride, thromboxane A2 inhibitor, and antioxidants could improve HMP preservation and minimize reperfusion injury of warm ischemic livers. Preflushed rat livers subjected to 60 min WIT were preserved for 5 h with standard UW or supplemented UW (SUW) solution. Post preservation hepatic functions and viability were assessed during isolated perfusion with Krebs-Henseleit solution. Livers preserved with SUW showed significantly (p < .001) improved recovery of tissue ATP levels (micromol/g liver), 2.06 +/- 0.10 (mean +/- SE), as compared to the UW group, 0.70 +/- 0.10, and the level was 80% of that of fresh control livers (2.60 +/- 0.13). At the end of 1 h of rewarming, lactate dehydrogenase (U/L) in the perfusate was significantly (p < .05) lower in the SUW group (429 +/- 58) as compared to ischemia-reperfusion (IR) (781 +/- 12) and the UW group (1151 +/- 83). Bile production (microg/min/g liver) was significantly (p < .05) higher in the SUW group (280 +/- 13) as compared to the IR (224 +/- 24) and the UW group (114 +/- 14). The tissue edema formation assessed by tissue wet-dry ratio was significantly (p < .05) higher in UW group. Histology showed well-preserved hepatic structure in the SUW group. In conclusion, this study suggests that HMP with SUW solution has the potential to restore and preserve livers with extended WIT.     

Hemodynamic and biochemical changes during normothermic and hypothermic sanguinous perfusion of the porcine hepatic graft

Using an ex vivo liver sanguinous perfusion system, hemodynamic and biochemical changes of the porcine livers were studied, which were preserved cold (4 degrees C) for 24 hr in University of Wisconsin solution and reperfused with normothermic (37 degrees C) (n = 8) or hypothermic (32 degrees C) (n = 8) blood for 3 hr. Six more livers were reperfused with normothermic blood (37 degrees C) immediately after procurement as controls. The total hepatic blood flow was adjusted to 1 ml/min/g liver weight, in which hepatic artery and portal vein flows were administered at a 1:2 ratio. In livers stored cold for 24 hr in UW solution and perfused normothermically, a statistically higher hepatic artery resistance was exhibited at 30 and 60 min after reperfusion (P less than 0.05), and there was lower bile output (P less than 0.05) at 90 and 120 min as compared to the controls. In livers stored cold for 24 hr in UW solution and perfused hypothermically, as compared to ones perfused normothermically, statistically higher hepatic-artery and portal-vein resistances (P less than 0.05) were observed throughout the perfusion period and 60 min after reperfusion, respectively. In addition, bile output and oxygen consumption of these livers were statistically lower than those of ones perfused normothermically (P less than 0.05). In contrast, chemistries of the perfusate of livers perfused hypothermically were comparable to ones perfused normothermically. Histologic examination of the liver perfused hypothermically demonstrated hepatic arterial and/or portal venous congestion and mild-to-moderate hemorrhage in the portal triads. This study suggests that livers preserved for a prolonged period of time demonstrate a high hepatic arterial resistance shortly after revascularization, and that recipient hypothermia after revascularization may be a risk factor for the development of hepatic arterial thrombosis following liver transplantation.     

Hypothermic machine perfusion of liver grafts for transplantation: technical development in human discard and miniature swine models

INTRODUCTION: Cold storage (CS) is the standard preservation technique for liver transplantation (LTx). Hypothermic machine perfusion (HMP) is an alternative preservation technique that provides a continuous supply of substrates and removes waste products. HMP improves early graft function in kidney transplantation, especially for marginal organs: To our knowledge there have been no reports HMP in human LTx. The aim of this study was to develop a reproducible technique for liver HMP prior to initiating a clinical trial. METHODS: For the discard protocol, between May 2001 and March 2002, 10 nontransplantable human livers were obtained. We designed a model of atraumatic, centrifugal HMP of the portal vein (PV) and hepatic artery (HA) via donor vascular conduit. Livers were perfused at 3 degrees C to 5 degrees C with Vasosol solution for 5 to 10 hours using a modified Medtronic Portable Bypass System. Perfusion variables (temp, flow, pressure) where recorded every 30 minutes. During the study, we also validated our techniques in an animal model. For the animal protocol; six swine were used as liver donors and randomized to 12 hours of CS in UW (n = 3) or 12 hours of HMP using Vasosol solution (n = 3). LTx was performed in six swine. Animals survived until postoperative day 5. RESULTS: For the discard protocol, mean HMP time was 6.7 +/- 1.8 hours. Target flow was 0.7 mL/g liver/min. PV and HA pressure ranged from 3 to 5 and 12 to 18 mm Hg, respectively. All grafts were maintained at 3 degrees C to 5 degrees C during HMP. For the animal protocol, all recipients had good liver function and survived to postoperative day 5. AST and TBili were similar between CS and HMP. CONCLUSIONS: Our method of liver HMP appears to be a safe and reliable method to preserve livers. A clinical trial is now underway to evaluate this technique in human LTx.     

Survival transplantation of preserved non-heart-beating donor rat livers: preservation by hypothermic machine perfusion

BACKGROUND: Non-heart-beating donor (NHBD) livers are an untapped source with the potential to provide relief to the current donor shortage problem. Hypothermic machine perfusion (MP) has the potential to reclaim and preserve these marginal donor organs. METHODS: This study compared 5-day survival in a rat NHBD liver transplantation model with simple cold storage (SCS) and MP-preserved tissues that had experienced 30 min of warm ischemia followed by a 5-hr preservation period with the University of Wisconsin solution. Total release of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT) were determined at major time points. Bilirubin levels and histology were examined after 5-day survival. RESULTS: Six of seven control livers and five of six MP livers survived, whereas SCS tissues had survival in zero of seven. The results showed that MP livers had reduced release of LDH and ALT after 5 hr of storage, 5.07+/-1.42 and 2.02+/-0.69 U (mean+/-SE), respectively, compared with SCS, 15.54+/-0.81 and 3.41.3+/-0.73 U, respectively. Bilirubin values after 5-day survival of MP livers (1.17+/-0.49 mg/dL) were comparable to controls (0.91+/-0.36 mg/dL). Histology confirms that SCS displayed increased necrosis and MP tissue showed regions of near normal hepatic structure. CONCLUSIONS: These results suggest that MP for 5 hr improves survival and reduces cellular damage of liver tissue that has experienced 30 min of warm ischemia when compared with SCS tissues. Further studies need to be conducted, but this study suggests that MP preservation has the potential to reclaim and preserve NHBD liver tissues.     

Effects of exogenous endothelin-1 application on liver perfusion in native and transplanted porcine livers

PURPOSE: This study was designed to assess and differentiate the impact of progressivly increasing portal venous endothelin-1 (ET) plasma concentrations on hepatic micro- and macroperfusion of native porcine livers (Group A) and liver grafts after experimental transplantation (Group B). METHODS: A standardized gradual increment in systemic ET plasma concentration (0-58 pg/ml) was induced by continuous ET-1 infusion into the portal vein in both groups (A: n = 10, B: n = 10). Control animals received only saline (n = 5, each group). Hepatic microcirculation (HMC) was quantified by thermodiffusion electrodes, hepatic artery flow (HAF), and portal venous flow (PVF) by Doppler flowmetry. RESULTS: No changes in ET or perfusion parameters were observed in controls. The mean ET level after orthotopic liver transplantation (OLT) in Group B was elevated (baseline: 3.8 +/- 2.4 pg/ml) compared with Group A (2.8 +/- 1.9 pg/ml). With rising ET levels HAF decreased progressively in Group A from 205 +/- 97 (baseline) to 160 +/- 72 ml/min, and in Group B from 161 +/- 87 to 146 +/- 68 ml/min. PVF decreased in Group A from 722 +/- 253 to 370 +/- 198 ml/min, and in Group B from 846 +/- 263 to 417 +/- 203 ml/min. Baseline HMC in Group A was 86 +/- 15 and decreased significantly to 29 +/- 9 ml/100 g/min, and baseline MC in Group B was 90 +/- 22 and decreased to 44 +/- 32 ml/100 g/min. No significant alteration in systemic circulation was noted at the ET concentrations investigated. CONCLUSIONS: Significant impairment of hepatic micro- and macrocirculation was detected after induction of systemic ET levels above 9.4 pg/ml both in native and in transplanted livers. Disturbance of HMC was caused predominantly by reduction of portal venous flow, while the effect of ET on HAF was less pronounced. Characteristics of flow impairment in transplanted and native livers were analogous after short cold ischemic graft storage (6 h).     

运用CT灌注成像监测介入断流术后肝脏血流灌注的变化

目的运用CT灌注成像评价肝硬化门静脉高压症患者介入断流术后肝脏血流灌注的变化。方法收集2001年6月至2006年5月间23例肝硬化门静脉高压症患者,其中15例行部分脾栓塞术、8例行部分脾栓塞术联合胃冠状静脉栓塞术;术前后采用东芝Xpress型螺旋CT行单层肝脏动态增强扫描,同时测定主动脉、门静脉和肝脏感兴趣区的CT值,取增强的CT值绘制时间密度曲线。去卷积法计算肝脏各灌注参数。结果部分脾栓塞术后肝脏门静脉灌注量有所减少,但肝动脉灌注量增加,总肝灌注量与术前差异无统计学意义（t＝-0．677,P〉0．05）,肝动脉灌注指数从12．5％升至32．5％。部分脾栓塞术联合胃冠状静脉栓塞术术前肝脏门静脉灌注量为0．862ml·min^-1·ml^-1,术后为0．722ml·min^-1·m^-1,两者差异无统计学意义（t=-0．281,P〉0．05）,肝动脉灌注量、总肝灌注量分别由术前的0．128、0．990ml·min^-1·ml^-1。增加至术后的0．290、1．021ml·min^-1·ml^-1。结论螺旋CT灌注成像能客观反映肝硬化门静脉高压症患者部分脾栓塞术、胃冠状静脉栓塞术术后肝血流动力学的变化。     

Biliary secretion of extracorporeal porcine livers with single and dual vessel perfusion.

BACKGROUND: Hepatic support systems that provide detoxification without biliary secretion (i.e., isolated hepatocyte systems) are sufficient to improve encephalopathy and bridge patients to transplantation. However, biliary secretion may be critical when hepatic support attempts to restore function and regeneration of the host liver. The purpose of these studies was to optimize the support liver secretory response to bile acid by either single-vessel (portal vein; PV) or dual-vessel (hepatic artery [HA] + PV) perfusions during extracorporeal porcine liver perfusion. METHODS: Extracorporeal porcine liver perfusion of anesthetized pigs was developed using support porcine livers perfused through the PV (n=4) alone and through the HA + PV (n=4) via a venovenous circuit. Support livers were provoked with taurocholate (TC) to enhance bile aqueous and hydrophobic outputs. RESULTS: After cold preservation and reperfusion, both PV and HA + PV livers had initial 1-hr bile aqueous outputs < 15% of in vivo flow, with cholesterol (C) and phospholipid (PC) outputs <25% of in vivo flow. Bile flow was significantly greater for recovered HA + PV livers (3.0+/-0.01 ml/15 min) than PV livers (1.9+/-0.01 ml/15 min). Despite this, PC output was significantly greater for PV than HA + PV livers. The C/PC ratio of PV livers was twice that of HA + PV livers. TC infusion (48 micromol/kg/15 min) of HA + PV livers demonstrated significantly greater increments in bile flow, PC output, and C output than PV livers. CONCLUSION: In the unstimulated state, porcine support livers with dual-vessel perfusion generated greater aqueous and C outputs despite diminished PC output than in those with single-vessel perfusion. TC stimulation increased bile flow, PC output, and C output in dual-perfused livers more than in PV livers. HA + PV perfusion of support livers is the preferred technique for removing hydrophobic compounds that require PC transport for excretion or exist in the aqueous phase.     

Protagonism of the arterial circulation in the preservation of the pig's liver by simple perfusion and hypothermic storage

A modified technique to perform the successive perfusions of the liver that are necessary for its preservation by the simple perfusion method and hypothermic storage is presented. This technical variety has been tested on Large White pig's livers and consists in doing the successive perfusions of cooling, preservation and washout, first through the hepatic artery and there after through the portal vein. The macroscopic and biochemical characteristics of the effluents obtained through the infrahepatic inferior vena cava during the perfusion-washout of the livers at the end of the period cold ischemia shows its effectiveness. Likewise, the hepatic perfusion-washout begun via the arterial vein and finished via the portal one avoids post-revascularization hyperpotassemia in the receptor animals. It is hypothesized that the arterial protoganism of perfusions, when the simple perfusion and hypothermic storage method of hepatic preservation is used, could be a prophylaxis against complications of a post-transplant biliary origin.     

Seventy-two-hour preservation of the canine liver by machine perfusion

The UW solution effectively preserves the dog liver for up to 48 hr by simple cold storage. This solution contains lactobionate as the primary impermeant. Another solution developed for machine perfusion of the kidney is similar to the UW solution but contains gluconate in place of lactobionate. In this study the UW gluconate solution was used for the continuous hypothermic machine perfusion of dog livers for 72 hr. Dog livers were continuously perfused at 5 degrees C through the portal vein at a pressure of 16-18 mm Hg and transplanted. Seven of 8 dogs survived for 7 or more days following orthotopic transplantation. The livers functioned as well as those preserved for 48 hr by cold storage in the UW solution as indicated by various liver-function tests. Successful machine perfusion was only achieved when the perfusate contained a high concentration of potassium (125 mM) but not with a high concentration of sodium (125 mM). This study demonstrates the feasibility of machine-perfusion preservation of the liver that yields longer preservation of equal quality compared to simple cold storage. For the development of truly long-term preservation (5 or more days) and better quality short-term preservation, machine perfusion may be the method of choice.     

Functional recovery of preserved livers following warm ischemia: improvement by machine perfusion preservation

BACKGROUND: Hypothermic machine perfusion preservation has the potential to relieve the current donor shortage problem by reclaiming and preserving marginal donor organs including those from viable non-heart-beating donors. A number of problems exist with the current machine perfusion technology for preserving livers, and much research is needed to determine the clinical impact of this technology in preserving non-heart-beating donor livers. METHODS: This study was conducted to compare the poststorage function and microcirculation of simple cold stored and machine perfusion preserved livers that had experienced 30 min of warm ischemia followed by a 10 hr preservation period. In an isolated rat liver perfusion model, lactate dehydrogenase activity, indocyanine green secretion, and portal pressure values were determined at major time points. An intravital microscopy was conducted to assess microcirculation. RESULTS: The results showed an increase in flow homogeneity of machine perfused livers, which correlated with the reduction in portal pressure when compared with simple cold storage (5.4+/-0.4 vs. 8.7+/-0.6 mm Hg). A reduction in lactate dehydrogenase levels in the perfusate (333+/-22 vs.103+/-8 U/L) and an increase in bile production of the machine perfused livers (4.9+/-0.5 vs. 33.2+/-1.7 microg/min/g liver) and indocyanine green secretion (11.7+/-1.7 vs. 21.2+/-2.1 Abs/g bile) were observed at all time points (mean+/-SE of final point given). Intravital microscopic examination indicated that large regions of non flow, as indicated by the absence of fluorescein isothiocyanate-labeled albumin, were observed in the simple cold stored tissue, whereas machine perfused liver showed increase flow homogeneity. Values of bile production, indocyanine secretion, and cellular damages were comparable with controls. Histologic examination confirmed that simple cold stored tissue displayed increased vacuolization, and machine perfused tissue showed regions of normal hepatic structure. CONCLUSION: These results suggest that machine perfusion for 10 hr improves both poststorage function and microcirculation while reducing cellular damage of liver tissue that has experienced 30 min of warm ischemia, when compared with simple cold storage. Further studies need to be conducted, but this study suggests that machine perfusion preservation has the potential to reclaim and preserve liver tissues after warm ischemic insult.     

Verapamil improves rat hepatic preservation with UW solution

Verapamil, a calcium channel blocker, improves myocardial preservation during cold cardioplegia and protects against renal damage during periods of warm and cold ischemia. To determine if verapamil could prevent ischemic damage to livers during and after cold storage, harvested rat livers were flushed with either University of Wisconsin (UW) solution or UW solution with 25 mg/liter verapamil. Twenty rats were used in each group. After 24 hr of storage at 4 degrees C, livers were perfused with oxygenated blood through the portal veins for 2 hr at 37 degrees C and pH 7.4. Liver enzymes, electrolytes, and perfusate flow rate were determined at 30-min intervals. At 90 min of perfusion, the verapamil group of livers had less elevation of AST (110 +/- 17 IU/liter vs 172 +/- 25 IU/liter, P less than 0.05), ALT (115 +/- 21 IU/liter vs 210 +/- 34 IU/liter, P less than 0.05), and LDH (962 +/- 170 IU/liter vs 1452 +/- 253 IU/liter, NS). Verapamil livers produced more bile than controls (6.9 +/- 1.9 microliters/g vs 2.3 +/- 1.7 microliter/g, P less than 0.05) and maintained a higher portal flow rate throughout the perfusion. Both groups showed similar reduction in liver weights after storage (3.9 +/- 0.9% vs 2.8 +/- 0.7%) and required the same amount of bicarbonate for correction of acidosis during perfusion (2.6 +/- 0.2 mM vs 2.8 +/- 0.2 mM). Light microscopic exam after perfusion showed hepatocyte damage in 30% of control livers, but 0% of verapamil livers. We conclude that verapamil-treated rat livers showed less damage and better function upon reperfusion after 24 hr of cold storage. This agent may be clinically useful as an additive to the UW preservation solution for livers.     

低温机械灌注对大鼠肾脏炎症因子表达水平的影响

目的 探讨低温机械灌注（HMP）对大鼠肾脏炎症因子表达水平的影响。 方法  雄性大鼠30只,随机分为对照组（Control组）,静态冷保存组（SCS组）和HMP组,每组10只。记录HMP过程中流速、肾内阻力和灌注流出液pH值。收集每组肾脏组织,采用逆转录聚合酶链反应（RT-PCR）检测CXC趋化因子配体（CXCL）1、CXCL2、干扰素（IFN）-β1、IFN-α4、CC趋化因子配体（CCL）2、CCL20、白细胞介素（IL）-17α、IL-17C和肿瘤坏死因子（TNF）-α的信使RNA（mRNA）表达水平,苏木素-伊红（HE）染色观察肾脏组织病理学改变。 结果  HMP过程中的流速、肾内阻力保持稳定,灌注流出液pH值缓慢降低。RT-PCR结果显示,与Control组比较,SCS组和HMP组CXCL1、CXCL2、CCL2、CCL20、IL-17α、IL-17C和TNF-α的mRNA相对表达量升高;与SCS组比较,HMP组CXCL1、CXCL2、CCL2、CCL20、IL-17α和TNF-α的mRNA相对表达量升高（均为P<0.05）。HE染色结果显示,Control组肾脏细胞形态正常,SCS组出现明显的上皮坏死、胞质空泡化、刷状缘丢失、上皮脱落,与SCS组比较,HMP组病理改变程度减轻。 结论  HMP能激活肾脏炎症反应,抑制HMP过程中的炎症反应激活有望进一步提高移植物保存效果。     

贲门周围血管离断术前后肝硬化病人肝脏血流灌注的改变

目的：利用肝脏阻抗血流图探讨肝硬化门静脉高压症病人的肝脏血流灌注改变和贲门周围血管离断术对肝脏血流灌注的影响。方法：选取22例肝硬化门静脉高压症病人，分别在术前1周、术后2周检测肝血流阻抗改变，同时用Doppler检测门静脉血流动力学变化。结果：阻抗血流图表明，和对照XEG相比，门静脉高压症病人的肝动脉、门静脉向肝血流灌注明显下降，总肝灌注量降低；门静脉高压症病人术后门静脉向肝灌注增加，肝动态的向肝灌注无显著改变。Doppler测定表明门静脉高压症病人的门静脉直径增加，血流量增加，但血流速度无显著差别；术后门静脉血流动力学与术前无差别。结论：肝硬化病人肝动脉、门静脉向肝有效血流灌注都降低，肝脏总血流量下降；贲门周围血管离断术增加大部分病人的门静脉向肝血流灌注，但对肝动脉的向肝灌注无显著影响；肝脏阻抗血流图作为反映肝脏动态血流灌注的无创性检查，对于评价肝硬化病人的肝脏血流及评价手术对肝脏血流动力学的影响有一定的价值。