Function and metabolism of canine kidneys after aerobic ischemia by orthograde persufflation with gaseous oxygen

Persufflation—Current State of Play

With the ever-increasing disparity between the number of patients waiting for organ transplants and the number organs available, some patients are unable to receive life-saving transplantation in time. The present, widely-used form of preservation is proving to be incapable of maintaining organ quality during long periods of preservation and meeting the needs of an ever-changing legislative and transplantation landscape. This has led to the need for improved preservation techniques. One such technique that has been extensively researched is gaseous oxygen perfusion or Persufflation (PSF). This method discovered in the early 20th century has shown promise in providing both longer term preservation and organ reconditioning capabilities for multiple organs including the liver, kidneys, and pancreas. PSF utilises the organs own vascular network to provide oxygen to the organ tissue and maintain metabolism during preservation to avoid hypoxic damage. This review delves into the history of this technique, its multiple different approaches and uses, as well as in-depth discussion of work published in the past 15 years. Finally, we discuss exciting commercial developments which may help unlock the potential for this technique to be applied at scale.

Retrograde Flushing of Living Donor Renal Allografts via the Renal Vein: A Simple, Effective Technique

BACKGROUND

Prograde flushing (PF) of living donor renal allografts with preservation solution via the renal artery or arteries is standard practice. PF may be difficult and potentially injurious to the donor kidney, especially in grafts with small or multiple arteries. In this report, we present our experience with retrograde flushing (RF) of 7 living donor kidneys via the renal vein.

METHODS

Retrospective review of 7 consecutive living donor renal transplants performed using the RF technique was performed. The 7 preceding living donor renal transplants performed using the standard arterial PF technique served as a control group.

RESULTS

All 7 recipients of RF kidneys experienced immediate graft function. At postoperative days 3 and 30, there was no difference in estimated glomerular filtration rate between the RF study group and PF controls.

CONCLUSIONS

The RF technique is simple and safe, with results equivalent to the PF technique. The RF technique may be especially useful after recovering kidneys with small and/or multiple arteries.

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.

A comparison of the metabolic effects of continuous hypothermic perfusion or oxygenated persufflation during hypothermic storage of rat liver

The metabolic consequences of supplying oxygen by two different modes were investigated. The effects of hypothermic liver preservation after cold hypoxic flush (Group I), oxygenated vascular persufflation (Group II), and continuous oxygenated perfusion (Group III) were compared. Adenine nucleotides were measured to assess energetics, and 1H nuclear magnetic resonance spectroscopy was employed to investigate other metabolic pathways. Energetics were maintained by both modes of oxygenation at 24 h. The mitochondrial redox state is indicated by the ratio of acetoacetate (Ace) and beta-hydroxybutyrate (betaHb). The detection of only betaHb or Ace in the hypoxic flush and perfused livers, respectively, suggested that the mitochondria of these livers were hyperreduced and hyperoxidized, respectively. In contrast, both components of the redox couple were detected in the persufflated livers, suggesting that persufflation may be a simple and effective method of maintaining hepatic energetics long-term while maintaining a more normal mitochondrial redox state.

Reduction in nonparenchymal cell injury and vascular endothelial dysfunction after cold preservation of the liver by gaseous oxygen

Reintroduction of oxygen to previously anoxic tissue may result in severe cell injury (oxygen paradox) and contribute to the so-called reperfusion damage of ischemic organs. Our study investigated the influence of simple gaseous oxygen supply during ischemia on nonparenchymal cell alterations upon reperfusion of the liver. Livers from male Wistar rats were isolated, rinsed blood-free and stored for 48 h at 4 degrees C in UW-preservation solution (group 1; n = 6). Gaseous oxygen was insufflated into a second group of livers (group 2; n = 6) during the storage period via the inferior caval vein at a pressure limited to 18 mmHg. To simulate the period of slow rewarming of the organ during surgical implantation in vivo, all livers were incubated at 25 degrees C in saline solution for 30 min prior to reperfusion. Reperfusion was carried out in vitro in a recirculating system with Krebs-Henseleit buffer. A control group was perfused immediately after harvest. The technique of aerobic storage (group 2) resulted in normal vascular perfusion characteristics without elevation of portal venous pressure (PVP) above control values, in contrast to group 1 livers which showed a significantly elevated PVP, averaging between 1.5 and 2 times the values of the control. Hepatic efflux of NO (nmol/ml) after 10 min of reperfusion was massively increased in group 1, while only low concentrations were found in group 2 and in control livers. Kupffer cell activation after ischemia was shown by a huge increase in acid phosphate release upon reperfusion compared with the control, with significantly lower values in group 2 after 10 min of reperfusion than in group 1. Thus, aerobic ischemia by gaseous oxygen persufflation seems an appropriate tool for long-term organ preservation, preventing vascular and parenchymal dysfunction upon reperfusion.

Reduction in nonparenchymal cell injury and vascular endothelial dysfunction after cold preservation of the liver by gaseous oxygen

Reintroduction of oxygen to previously anoxic tissue may result in severe cell injury (oxygen paradox) and contribute to the so-called reperfusion damage of ischemic organs. Our study investigated the influence of simple gaseous oxygen supply during ischemia on nonparenchymal cell alterations upon reperfusion of the liver. Livers from male Wistar rats were isolated, rinsed blood-free and stored for 48 h at 4 degrees C in UW-preservation solution (group 1; n = 6). Gaseous oxygen was insufflated into a second group of livers (group 2; n = 6) during the storage period via the inferior caval vein at a pressure limited to 18 mmHg. To simulate the period of slow rewarming of the organ during surgical implantation in vivo, all livers were incubated at 25 degrees C in saline solution for 30 min prior to reperfusion. Reperfusion was carried out in vitro in a recirculating system with Krebs-Henseleit buffer. A control group was perfused immediately after harvest. The technique of aerobic storage (group 2) resulted in normal vascular perfusion characteristics without elevation of portal venous pressure (PVP) above control values, in contrast to group 1 livers which showed a significantly elevated PVP, averaging between 1.5 and 2 times the values of the control. Hepatic efflux of NO (nmol/ml) after 10 min of reperfusion was massively increased in group 1, while only low concentrations were found in group 2 and in control livers. Kupffer cell activation after ischemia was shown by a huge increase in acid phosphate release upon reperfusion compared with the control, with significantly lower values in group 2 after 10 min of reperfusion than in group 1. Thus, aerobic ischemia by gaseous oxygen persufflation seems an appropriate tool for long-term organ preservation, preventing vascular and parenchymal dysfunction upon reperfusion.

The effects of allopurinol and SOD on lipid peroxidation and energy metabolism in the liver after ischemia in an aerobic/anaerobic persufflation

This study was aimed at examining the vulnerability of the liver to oxygen-free radicals upon reoxygenation after prolonged ischemia. Livers from male Wistar rats were first flushed with Ringer's and Euro-Collins solutions. After ischemic storage in Krebs-Henseleit solution at 37 degrees C for 60 min and in Euro-Collins solution at 4 degrees C for another 60 min, they were then persufflated with either gaseous O2 or N2 for 30 min at 37 degrees C, and rinsed again with Ringer's solution. Enzyme concentrations and calcium ion activities were measured in the effluent rinsing solution after passage through the liver. Treatment with superoxide dismutase (SOD) or allopurinol resulted in a significant reduction of tissue injury, determined by the enzyme loss, calcium uptake, and lipid peroxidation upon persufflation with O2. Allopurinol also improved the tissue levels of ATP and the sum of adenine nucleotides after aerobic persufflation, whereas SOD did not. Notwithstanding, neither treatment had any effect on anoxic persufflation with N2. Thus, we conclude that the postischemic liver is susceptible to oxygen-induced free radical injury and that allopurinol and SOD promote specific antioxidative protection of the liver, with the exclusion of side effects related to substrates or perfusion modalities.