Liver and kidney preservation by perfusion.

The clinical boundaries of transplantation have been set in an era of simple cold storage. Research in organ preservation has led to the development of flush solutions that buffer the harsh molecular conditions which develop during ischaemia, and provide stored organs that are fit to sustain life after transplantation. Although simple and efficient, this method might be reaching its limit with respect to the duration, preservation, and the quality of organs that can be preserved. In addition, flush preservation does not allow for adequate viability assessment. There is good evidence that preservation times will be extended by the provision of continuous cellular substrate. Stimulation of in-vivo conditions by ex-vivo perfusion could also mean that marginal organs will be salvaged for transplantation. Perfusion will also allow for assessing the viability of organs before transplantation in a continuous fashion. The cumulative effect of these benefits would include expansion of the donor pool, less risk of primary non-function, and extension of the safe preservation period. Use of non-heart-beating donors, international organ sharing, and precise calculation of the risk of primary organ failure could become standard

The non-heart-beating donor: Bridging the gap to the future

Renal grafts from NHBDs result in long-term function that does not compromise current clinical standards and therefore make the NHBD a viable way to expand the donor pool. Several programs around the world are beginning to use NHBD livers in clinical transplantation; thus, there is certain to be a surge of reports appearing in the literature in the near future. It appears from available data to date that NHBD livers retrieved in a controlled fashion from category 3 donors may offer a safe source for more organs. Further research and clinical experience with NHBD transplantation for both kidney and liver should help define reproducible and acceptable methods. However, until an alternative source of organs becomes available, the NHBD represents an increasingly important means to alleviate the growing demand for transplant organs

Hepatic steatosis and its relationship to transplantation.

Fatty infiltration of the liver is common in the brain-dead donor population and has a strong correlation with primary nonfunction after cold preservation, a condition that is catastrophic to liver transplant recipients. This literature review examines factors associated with the development, diagnosis, quantification, and clinical management of this difficult condition

Current practice regarding the use of fatty livers: a trans-Atlantic survey.

A strong association exists between the presence of steatosis in a donor liver for transplantation and the development of primary nonfunction in the recipient. Despite this, appraisal of the donor remains one of the least scientific aspects of the transplantation process, and many centers base their practice on subjective opinion, rather than objective data. We conducted this survey to illuminate controversial issues and highlight the variation of opinion and practice policies both between and within the United Kingdom and the United States. A simple, anonymous, one-page, 10-question survey with tick-box answers was sent to every practicing liver transplant surgeon in the United Kingdom. The same form was sent by E-mail to liver transplant surgeons in the United States with a current E-mail address listed in the American Society of Transplant Surgeons registry. In the United Kingdom, 16 of 19 surgeons polled responded (84.2%) and thus were considered representative. From the United States, there were 78 respondents from 52 centers, representing all 11 United Network for Organ Sharing regions. We found that current practice policies differ not only between nations, but also among centers in each country. US surgeons generally follow a more conservative approach, with greater emphasis on histological assessment. Dichotomous opinions exist on the significance of microvesicular steatosis in both countries. Most evident from this survey is that more research in the field is required to help answer these questions and allow for the safe use of all viable livers

Extended preservation of non-heart-beating donor livers with normothermic machine perfusion.

BACKGROUND: Non-heart-beating donor (NHBD) livers represent an important organ pool, but are seldom utilized clinically and require rapid retrieval and implantation. Experimental work with oxygenated perfusion during preservation has shown promising results by recovering function in these livers. This study compared sanguinous perfusion with cold storage for extended preservation of the NHBD liver in a porcine model. METHODS: Porcine livers were subjected to 60 min of in vivo total warm ischaemia before flushing, after which they were preserved by one of two methods: group 1 (n = 4), University of Wisconsin (UW) solution by standard cold storage for 24 h; group 2 (n = 4), oxygenated autologous blood perfusion on an extracorporeal circuit for 24 h. All livers were subsequently tested on the circuit during a 24-h reperfusion phase. RESULTS: Livers in group 1 showed no evidence of viability during the reperfusion phase with no bile production or glucose utilization; they also displayed massive necrosis. Livers in group 2 demonstrated recovery of function by synthetic function, substrate utilization and perfusion haemodynamics; these livers displayed less cellular injury by hepatocellular enzymes. All differences in parameters between the two groups were statistically significant (P < 0.05). These findings were supported by histological examination. CONCLUSION: Warm ischaemia for 1 h and simple cold storage (UW solution) for 24 h renders the liver non-viable. Oxygenated, sanguinous perfusion as a method of preservation recovers liver function to a viable level after 24 h of preservation

Optimisation of an enzymatic method for beta-galactosidase.

BACKGROUND: The enzyme beta-galactosidase present in the Kupffer cells of the liver has potential as a marker of liver dysfunction prior to transplantation. Spectrophotometric methods have insufficient sensitivity. METHODS: Fluorimetric methods have the required sensitivity and we have optimised such a method in a microtitre plate format to improve its utility. beta-galactosidase acts on the substrate 4-methylumbelliferyl-galactoside (MUG) to produce 4-methylumbelliferone (4-MU), detected fluorimetrically with excitation wavelength 355 nm and emission wavelength 460 nm. RESULTS: Reaction conditions in a citrate-phosphate buffer were optimised to give maximal enzyme activity: pH was optimal at 4.4 (range investigated 3.6-5.0) and substrate concentration at 3.33 mmol/l. A small specimen volume (10 microl) in 80 microl of substrate solution produced adequate fluorescent yield after an incubation period of 30 to 60 min at 37 degrees C. Reaction was terminated by addition of 200 microl of glycine-NaOH, pH 12.8. The assay is linear to 3,000 U/ml. The intra-assay coefficient of variation (CV%) at 50, 502, and 2,012 U/ml was 4.7, 3.1, and 3.4, respectively (n=10). Inter-assay CV% at 51, 496, and 1,986 U/ml was 7.0, 4.0, and 3.9, respectively (n=10). CONCLUSIONS: The assay has greater practical utility and demonstrated significant differences in the perfusate beta-galactosidase between cold-stored and warm-perfused livers in a porcine model of transplantation

Hepatic control of perfusate homeostasis during normothermic extrocorporeal preservation.

BACKGROUND: We investigated the ability of the isolated porcine liver to maintain acid-base homeostasis in the perfusate and the impact of ischemia-reperfusion injury without or with extracorporeal perfusion. METHODS: Harvested livers were either stored for 24 hours in cold University of Wisconsin solution or preserved by continuous, normothermic, oxygenated sanguineous perfusion with supplemental nutrition, prostacyclin, and bile salts. After a further 24-hour period of reperfusion of both groups on an extracorporeal circuit, the perfusate was assessed for both biochemical indices of synthetic and metabolic liver function as well as hepatocellular injury and blood gas analysis. RESULTS: Livers injured by cold ischemia during preservation displayed inferior synthetic and metabolic functions. Perfused livers, which displayed minimal ischemic injury, produced more bicarbonate than the cold-stored organs, suggesting autoregulation of pH homeostasis in perfused livers in contrast to progressively worsening acidosis in cold-stored organs. CONCLUSIONS: Given proper physiologic substrate the porcine liver has the ability to maintain acid-base homeostasis, provided there is not a significant ischemia-reperfusion injury