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A study was performed to determine the limiting factors to expanding the donor pool with warm ischemically (WI) damaged kidneys. Canine kidneys were damaged by 30 min of WI, and then either cold stored (CS) in ViaSpan (4 degrees C) for 18 h, or warm perfused with exsanguineous metabolic support (EMS) technology (32 degrees C) for 18h, or subjected to combinations of both techniques. The kidneys were autotransplanted with contralateral nephrectomy. In kidneys with WI and CS alone, the mean peak serum creatinine value was 6.3mg/dL and took 14 days to normalize. In contrast, kidneys where renal metabolism was resuscitated ex vivo during 18 h of warm perfusion demonstrated mild elevations in the serum chemistries (2.6mg/dL). The damage in kidneys CS for 18h was ameliorated with 3 h of subsequent warm perfusion and eliminated by 18 h of warm perfusion. In contrast, reversing the order with CS following WI and 18h of warm perfusion resulted in a time-dependent increase in damage. These results identify hypothermia as a major limiting factor to expanding indications for kidney donation. While hypothermia represents the foundation of preservation in the heart-beating donor, its use in WI damaged organs appears to represent a limiting factor.

The detrimental effect of prolonged cold ischemia (CI) on posttransplant renal function has long been recognized. However, the cellular consequences of CI have not been clearly defined. This study describes a model for the identification of CI-induced injury by evaluating ex-vivo renal metabolism and function prior to reperfusion. Small bovine kidneys were cold stored in Viaspan for 24-, 48-, 72-, and 96 h. Kidneys were then warm perfused (32 degrees C) using Exsangiunous Metabolic Support (EMS) technology and evaluated for oxidative metabolism, vascular dynamics and function. Oxygen consumption, vascular resistance, and diuresis were stable in kidneys with CI up to 48 h. After 72- and 96 h of CI, vascular resistance was increased while oxygen consumption and diuresis were reduced (P < 0.05). Glomerular filtration rate was diminished at CI greater than 24 h (P < 0.05). Results show that function was compromised with CI greater than 24 h and preceded the loss of cell viability following 48 h of CI.

Correlation between post-transplant function and exposure to cold ischemia (CI) during preservation has been reported. We attempted to identify the effect of CI on renal function using exsanguinous metabolic support (EMS) technology, to eliminate effects of reperfusion complications. Small bovine kidneys were used to evaluate 4 vs. 24 hours of CI, after warm ischemic (WI) exposure of <15, 30 or 60 minutes. After CI, kidneys were warm perfused (30 degrees C to 32 degrees C) ex vivo using EMS technology. Restored renal metabolism and function were quantified by oxygen consumption, urine production, glomerular filtration rate (GFR), and hemodynamic characteristics. The results demonstrate a CI-associated lag phase in the restoration of metabolism, in which the longer cold-preserved kidneys exhibit a lower initial rate of oxygen consumption. However, after 3 hours of EMS perfusion there was no significant difference in the O2 consumed, urine flow, GFR, perfusion flow, or pressure between the kidneys stored for 4 or 24 hours. An initial reduction in metabolism after longer CI may influence the severity of actual reperfusion injury during transplantation. Therefore, these results provide preliminary evidence suggesting that an acellular warm temperature reperfusion ex vivo may enhance restoration of cellular metabolism and minimize damage from the cold seen upon actual reperfusion.

For the past decades, severe hypothermia has represented the foundation of organ preservation in clinical transplantation. Beneficial as hypothermia has proven to be in preserving grafts from heart-beating donors, hypothermia does not seem to provide the window necessary for the prospective evaluation of organ function. With the increasing use of non-heart-beating donors, it is logical to propose that if organs are to be evaluated prospectively, it will be necessary to preserve them at warmer temperatures. Since both glomerular and tubular functions are inhibited at temperatures below 18 degrees C, such a goal will necessitate organ preservation at a temperature above 20 degrees C. The principle of preservation at warmer temperatures is not new, but with future developments and approaches, successful realization appears within reach. In this overview, a brief history of previous attempts at warm preservation, in the context of the current status of kidney preservation, is presented. Future developments and approaches, with the potential for prospective testing of the function and enhanced resistance to ischemic damage, will be discussed.

Several pathophysiological mechanisms have been purported to be involved in the development of acute ischemic renal failure, such as impairment of tubular function and/or of the renal microcirculation. However, it has not been elucidated as yet which of these mechanisms relates to the extent of kidney damage. Besides, little is known about the time course relationship between tubular and microcirculatory disturbances during the development of ischemia-reperfusion injury. We therefore performed intravital videomicroscopy of the proximal tubules as well as the peritubular microcirculation of the rat renal cortex during the first 24 hr of reperfusion after varying lengths of warm ischemia (30 min, 30 WI group; 60 min, 60 WI group; 90 min, 90 WI group). In a separate group of animals subjected to the same protocol, the survival rate (SR) was determined. The SR in these groups were 100%, 20% and 0%, respectively. Initially, the tubular and microcirculatory changes (i.e., increased tubular diameter and reduced capillary blood flow) relate well to the length of warm ischemia as well as the SR. At a later stage of reperfusion, however, we observed that peritubular capillary blood flow and tubular diameter recovered more quickly in the 90 WI group than in the 30 WI and 60 WI groups. As a result, these parameters as obtained at 24 hr of reperfusion did not relate anymore to the survival rate. Besides, at this stage a severe loss of integrity of the tubular wall was noted in the 60 WI and 90 WI groups. These findings suggest that kidney viability is not determined by the extent of recovery of microcirculatory blood flow and/or tubular diameter during early reperfusion, but by the integrity of the tubular wall.

Retrograde oxygen persufflation (ROP) has been reported to be beneficial to kidney preservation. The purpose of this study was to investigate whether use of ROP during cold storage (CS) with Universita of Wisconsin (UW) solution could ameliorate energy metabolism and functional recovery of ischemically injured rat kidneys and, moreover, to study the particular role of adenosine (ADO) in CS with ROP. Kidneys subjected to 30 min of warm ischemia (WI) were preserved for 24 h in 4 degrees C UW solution with or without ROP and with or without ADO. Measurements of tissue high-energy phosphate levels showed that reduced total adenine nucleotides (TAN) after 30 min of WI further declined during the subsequent CS. In ROP kidneys, however, TAN were less reduced, suggesting that even during CS, TAN can still be regenerated in the injured kidneys when ROP is combined with UW solution. When UW did not contain ADO, regeneration of TAN by ROP was slightly less than in the case of UW with ADO. This indicates that the supply of molecular oxygen is a significant factor in TAN resynthesis during CS. There was no statistically significant difference in survival rate between the ROP and CS groups, indicating that an improved energy status is not the sole determinant of functional recovery. We conclude that the gaseous oxygen supply provided by ROP during CS in UW solution ameliorates the energy state of ischemically injured rat kidneys and that exogenous ADO from the UW solution contributes to the improvement of energy metabolism to a limited extent.

The current shortage of transplantable organs has renewed interest in kidneys obtained from non-heart-beating donors. Kidneys from these donors have suffered warm ischemia (WI). The effectiveness of two preservation solutions, i.e., the University of Wisconsin (UW) and the histidine tryptophan ketoglutarate (HTK) solutions, for preservation of kidneys that have been subjected to WI was tested in dogs. The left kidney was autotransplanted after 30 min of WI, and subsequent 24-hr cold storage (CS) in either UW (n = 6) or HTK (n = 6), with immediate contralateral nephrectomy. Surgical biopsies from the cortex were taken before WI, after 30 min of WI, after 24 hr of CS, and after 1 hr of reperfusion for electron microscopy and for analysis of energy metabolites. At 2 weeks after transplantation in the UW group, 4 out of 6 and, in the HTK group, 1 out of 6 dogs survived. As from day 2, serum creatinine was lower in the UW group as compared with the HTK group (P < 0.05). After 24 hr of CS, in the HTK group the luminal membranes of proximal tubular cells were partly denuded of microvilli. Moreover, the tubular lumen was filled with blebs and debris. In the UW group, the brush borders remained intact, although microvilli were swollen. Energy metabolites were analyzed with HPLC. Thirty minutes of WI resulted in a +/- 45% reduction of total adenine nucleotide (TAN) content. During CS, TAN levels further decreased in both groups; however, after 24 hr of CS, the levels of adenosine, inosine, hypoxanthine, and xanthine were significantly higher in the UW group as compared with the HTK group (P < 0.05, P < 0.01, P < 0.01, P < 0.01). At 1 hr of reperfusion, TAN levels were higher in the UW group as compared with the HTK group (4.66 +/- 0.16 vs. 4.02 +/- 0.28, P < 0.05). Our results show that UW is a superior solution compared with HTK in the preservation of ischemically damaged kidneys, demonstrating better survival, better recovery of kidney function, better protection against ischemia-induced ultrastructural damage, and better preservation of energy metabolism indicated by (a faster) regeneration of TAN levels after reperfusion.

The growing success in renal transplantation has resulted in an increase in the need for donor organs. Procurement of kidneys from heart-beating (HB) donors is unlikely ever to meet this demand. Non-heart-beating (NHB) donors offer a yet untapped source of renal grafts. Cadaver kidneys from patients who have sustained cardiac standstill are often considered unsuitable for transplantation due to prolonged warm ischemia time. Using an emergency in situ perfusion technique it is possible to limit warm ischemic damage and to salvage these kidneys for transplantation. The procedure requires prompt action and cooperation of emergency service personnel. This report presents a protocol for the emergency in situ preservation procedure that can be practiced in most hospitals. At the University Hospital of Maastricht, The Netherlands, implementation of this procedure resulted in 20% more kidneys available for transplantation. Although NHB donor kidneys showed a higher rate of delayed function compared with a matched HB donor kidney population, there was no significant difference in long-term graft survival between the two groups.