Optimizing outcomes by preconditioning the donor.

The criteria that define a so-called "marginal donor" kidney have been standardized since 2002. However, every transplant center must establish its own guidelines on organ acceptability. An expanded criteria donor (ECD) kidney is age at least 60 years, or 50 to 59 years with at least two of three specified comorbidities. Cadaveric kidneys have shown worse functional and survival outcomes compared with those from living donors. Thus, all efforts should be made to minimize the effects of ischemia on standard, non-heart-beating or ECD cadaveric donor kidneys. Because of an increasing shortfall between the diminishing number of deceased donor organs available and the increasing waiting lists, an increasing number of living donor transplantations are being performed in Europe. Among deceased donor kidneys, the largest percentage corresponds to ECD--aged or comorbidity donors--and donors after cardiac death. The results of transplants with kidneys from donors over 65 years are 10% to 15% lower than those from younger donors. Older donors present more comorbidities; however, acceptable results may be obtained with careful selection and shortened cold ischemic times. If the transplant center uses these donors to expand the pool of available organs, the donor must be evaluated according to age, vascular condition, renal function, and comorbidity. If the donor is accepted, suitable questions are: Has the potential donor undergone maneuvers to improve the quality of the kidneys? Which kind of approaches should we perform? Should we only use the biopsy information for a decision?

[Technical aspects of isolated organ perfusion devices]. / Aspectos técnicos de los dispositivos de perfusión de órgano aislado.

An aspect of capital importance in the transplant field is the maintainance and preservation of organs during the ischemic phase. Organ susceptibility and injuries secondary to ischemia, organ procurement and transportation are still nowadays one of the main causes for organ failure. Effective artificial organ perfusion has remained a main goal for researchers in this field for more than 100 years. In the second half of the XXth century these techniques have been applied to experimental and clinical organ preservation, with the aim of extending the period of an effective storage (which guarantees an early and good function after the transplant). Primary goal of any organ preservation is to maintain integrity in every cell system in order to minimize those injuries which produces graft dysfunction.

[Pharmacological preconditioning with sildenafil of warm ischemic kidneys]. / Precondicionamiento farmacológico con sildenafilo del riñón con isquemia normotérmica.

OBJECTIVES: To evaluate the preconditioning effect of sildenafil administered preoperatively in kidneys subjected to a period of warm ischemia (WI), hypothermic perfusion (HP) or cold storage (CS) and finally, autotransplant (AT). MATERIAL AND METHOD: We studied 6 groups of autotransplanted kidneys: no-WI-inmediate AT (Group A); 45 min of WI + immediate AT (Group B); 45 min of WI + 60 min of HP + autotransplant (Group C); 45 min of WI + 60 min of CS + autotransplant (Group D); 100 mg of oral sildenafil preoperatively + 45 min of WI + autotransplant (Group E); 100 mg of oral sildenafil preoperatively + 45 min of WI+60 min of HP + autotransplant (Group F). Belzer solution was used for HP; UW-Viaspan for CS. Inmediately after the autotransplant (reperfusion period), we recorded in real time for 60 min the values of Renal vascular Flow (RVF) and Renal Vascular Resistance (RVR). Nitric Oxide levels in the cava and renal graft vein were recorded every 15 min during the 60 min of the reperfusion-study period. Conventional & Electronic microscopy were completed after the process. RESULTS: We obtained significant higher values of RVF and lower values of RVR in sildenafil groups (E and F) in comparison to the other groups (A-D) (Table 1). NO levels were also significantly higher in groups E and F (Fig. 1). Groups A, B, E and F showed integrity of tubule and endothelium in comparison to groups C and D in the microscopic study. CONCLUSIONS: We showed a beneficious effect of sildenafil in inmediate post-transplant reperfusion hemodynamic and biochemical parameters of kidneys subjected to a critical period of warm-ischemia.

[Hystologic and hemodynamic aspects of warm ischemic graft in relation to the preservation method]. / Caracterización histoló6gica y hemodinámica del injerto con isquemia caliente según el método de preservación.

OBJECTIVE: The non-heart-beating donor has been proposed as a solution to donor shortage for renal transplantation. Because the nature of such donors, the kidneys so derived have been damaged by primary warm ischemia (WI), and so potentially they may never function. Minimizing graft injury is especially important in case of transplantation form marginal donors because of a high rate of delayed graft function or primary nonfunction. The aim of this experimental study is to assess the structural and hemodynamic consequences of hypothermic perfusion (HP) versus cold storage (CS), in renal allograft after a period of WI. MATERIAL AND METHODS: We used 20 mini-pigs. WI was achieved by vascular pedicle occlusion during 45 min. We divided organs in 4 groups: A (n=5), kidneys with WI and then transplanted; group B (n=5), grafts with WI and implanted after HP with Belzer solution in our computerized perfusion system. Group C-control, (n=5) transplanted without WI and D (n=5) with WI and 60 min of CS in UW-Viaspan solution. All the procedure was recorded by a computerized data system. Renal vascular resistance (RVR) and renal vascular flow (RVF) were automatically calculated by means of mathematical formulas after renal transplantation. Subsequently histological study was completed in all cases. RESULTS: We observed two patterns after transplantation: (1). Initial increase of RVR with posterior decrease and increase of vascular flow: in organs with WI and HP prior to transplantation (group B) // organs transplanted without WI (group C-control). Electronic and conventional microscopy showed integrity of endothelial and tubule structure. (2). Initial decrease with posterior increase of RVR. Organs with WI (group A) // organs with WI and CS (group D). Structural study showed endothelial and tubule disruption. CONCLUSION: In our experimental model machine perfusion preserves endothelial and tubule structure of kidneys with WI. After transplantation the hemodynamic pattern of grafts with WI and HP is similar to the control group (without WI and direct transplantation).

[Ischemia-reperfusion syndrome and role of preservation graft technique after laparoscopic versus open nephrectomy in a experimental model of living donor kidney transplant]. / Evaluación del síndrome isquemia-reperfusión y papel de la preservación del injerto en la extracción renal laparoscópica versus abierta en un modelo experimental porcino de donante vivo.

INTRODUCTION: Delayed graft function alter living donor transplantation is a subject of debate. Delayed graft function can be partially explained by renal ischemia-reperfusion injury, when severe is associated with decreased graft survival. In this experimental living donor model study, we analyze the hemodynamic, histological and biochemical effects of laparoscopic nephrectomy. We also, analyze the effect of a pulsatile machine perfusion for kidney preservation during cold ischemia time. MATERIAL AND METHODS: Twenty large-white pigs (average weight 40-45 kgrs) were divided in 4 experimental groups: Group A: Laparoscopic nephrectomy+ immediate graft perfusion in pulsatile vacuum pump+autotransplant Group B: Laparoscopic nephrectomy+ immediate graft perfusion by gravity+autotransplant Group C: Open nephrectomy+immediate graft perfusion in pulsatile vacuum pump+autotransplant Group D: Open nephrectomy+ immediate graft perfusion by gravity+autotransplant Both laparoscopic and open nephrectomy were completed transperitoneally according to standardized technique. Hypothermic perfusion was done in a system designed in our lab. RESULTS: We observed a decreased renal artery flow in kidneys procured laparoscopically compared to open nephrectomy. We found an artery flow recovery during the first 60 minutes after revascularization. Renal machine perfusion during cold ischemia time seems to have no beneficial effect, but shows a deleterious effect on hemodynamic event for renal transplantation. Lower plasma nitric oxide level is observed in kidneys obtained by laparoscopy compared with open surgical technique. And finally, we also found higher histological damage in proximal tubular and endothelial cell, in kidneys obtained by laparoscopy compared with open surgery. CONCLUSIONS: In our experience: Laparoscopic nephrectomy versus open nephrectomy produces, in a model of living donor transplant, a lower value or renal blood flow and a higher value of renal vascular resistanse. These hemodynamic findings tend to normalize by 60 min after the reperfusion. A lower blood concentration of nitric oxide after the transplant was detected in laparoscopic group Vs open surgery group.

[Experimental renal preservation units: is this activity necessary in Spain?]. / Unidades de preservación renal experimental. Es necesaria esta actividad en España?

Renal graft preservation research is considered complementary but at the same time important activity in high-quality Kidney Transplant Programs. It provides information on limitations of kidneys to be transplanted and to discard those organs with high probability of failure. Unification of criteria in the selection of organs is essential. We think that this activity should be encouraged by Health Institutions although requires investment in staff and technology.

[Design of experimental models in surgical investigation]. / Diseño de modelos experimentales en investigación quirúrgica.

INTRODUCTION: Research in Medicine is essentially based on three knowledge resources: diseased people (natural and primary), cadaveric bodies (Pathology primary resource) and experimental animals, whom constitutes physiopathologic knowledge resource. Experimental advances reached in the last century have determined the change of the concept "experimental animal" to a wider term: "experimental model". OBJECTIVES: This paper tryes to clarify this concept. To attain this goal, we must define previous considerations in the meaning of the concept "experimental models" and its two key-elements: statistics and design of experiments.

Sildenafil improves immediate posttransplant parameters in warm-ischemic kidney transplants: experimental study.

OBJECTIVE: To evaluate in an experimental model the effects of the PDE5 inhibitor sildenafil on kidney grafts autotransplanted after a period of 45 minutes of warm ischemia and 60 minutes of hypothermic pump perfusion. METHODS: Nine laboratory large-white pigs were divided into two groups. Group A (n = 4): oral dose of 100 mg sildenafil was administered 1 hour before the surgery. Group B (n = 5): no sildenafil given. Right single nephrectomy was completed after a 45-minute period of warm ischemia by complete vascular clamping. Before the autotransplant, all kidneys were submitted to a 60-minute period of hypothermic pulsatile perfusion. Renal flow, arterial pressure, and renal vascular resistance were recorded in real time for 60 minutes after autotransplant. Nitric oxide levels were determined in blood samples of the renal vein at predefined intervals. Optical and electronic microscopy was performed on all organs at the end of the procedure. RESULTS: Renal vascular flow was significantly higher and renal vascular resistance significantly lower in the sildenafil group compared with the non-sildenafil group. No significant differences were observed in systemic arterial pressure values between both groups. Nitric oxide levels were significantly higher for all periods in the sildenafil group. No differences were observed in histological studies. CONCLUSION: Our experimental work suggested a positive effect of sildenafil on the immediate posttransplant outcome of warm-ischemic kidneys without systemic secondary effects.

[Normothermic ischemia effects in renal microcirculation]. / Caracterización de los efectos de la isquemia normotérmica en la microcirculación renal.

We report the results obtained in a experimental work designed to evaluate the consequences of warm ischemia in hypothermic isolated renal perfusion. We perfused a number of kidneys after a period of 45 min of vascular occlusion. An alternative group of kidneys were perfused without previous warm ischemia. Ureter was canulated in all the procedures and output collected during the HP. Creatinine was added to the perfusion solution initially in order to determine creatinine clearance. HP hydrodynamics was recorded on real time through a computerised system. According to the results, renal vascular resistance as well as CrCl were higher in ischemic kidneys. Both facts along with minimal differences in pathologic study suggest an increase in vascular tone of efferent-postglomerular arteriole during HP. HP was an adequate technique to minimize histologic consequences of ischemia. Mycrovascular an biochemical changes produced during HP may be produced, essentially, by dynamic causes.

[Recent advances in the comprehension of the effects of cold ischemia in kidney graft]. / Innovaciones en la compresión de los efectos de la isquemia fría en el injerto renal.

Cold ischemia is the best known method to preserve kidneys for transplant. However, it produces several detrimental effects. First, cellular necrosis. Secondarily, during the hypothermic period a mitochondrial injury process develops which makes the cell entering a pre-apoptotic state. This apoptosis occurs definitively in the reperfusion. Preservation solutions currently available are not perfect and are not able to avoid cold-related cell injuries. The addition of certain substances to UW solution (desferrioxamine) has shown experimentally a reduction in mitochondrial cold-related lesions. Isolated hypothermic kidney perfusion reduces initial graft dysfunction about 20% in comparison to hypothermic storage. This fact relates to important either economical as functional consequences.

Innovaciones en la compresión de los efectos de la isquemia fría en el injerto renal / Recent avances int he comprehension of the effects of cold ischemia in kidney graft

La isquemia fría es el mejor método actual para preservar el riñón para trasplante. Sin embargo condiciona, en primer lugar, un proceso de necrosis celular directo. En segundo lugar, durante el período de hipotermia se desarrolla un proceso de lesión mitocondrial que hace que la célula entre en un estado de apoptosis latente. Esta apoptosis se completa definitivamente en esta población celular en el momento de la revascularización. Las soluciones de preservación actualmente disponibles no son perfectas, y no pueden evitar este proceso. La adición de ciertas sustancias en la solución de UW ha demostrado experimentalmente (Desferrioxamina) una reducción de las lesiones mitocondriales producidas durante la fase de hipotermia. La utilización de perfusión de riñón aislado podría, comparativamente con la hipotermia simple, reducir la aparición de disfunción inicial del injerto hasta en un 20%, lo que tendría consecuencias importantes tanto funcionales como económicas (AU)

Cold ischemia is the best known method to preserve kidneys for transplant. However, it produces several detrimental effects. First, cellular necrosis. Secondarily, during the hypothermic period a mithocondrial injury process develops which makes the cell entering a pre-apoptotic state. This apoptosis occurs definitively in the reperfusion. Preservation solutions currently available are not perfect and are not able to avoid cold-related cell injuries. The adition of certain substances to UW solution (desferrioxamine) has shown experimentally a reduction in mitochondrial cold-related lesions. Isolated hypothermic kidney perfusion reduces initial graft dysfunction about 20% in comparison to hypothermic storage. This fact relates to important either economical as functional consequences (AU)

[Hydrodynamic and biochemical adaptation to perfusion pressure profile in isolated hypothermic renal perfusion]. / Perfusión hipotérmica del riñón aislado: respuesta hidrodinámica y bioquímica al perfil de aplicación de la presión.

OBJECTIVES: To evaluate hydrodynamic, biochemical and pathologic consequences of positive forced pressure on hypothermic isolated renal perfusions in comparison to softly progressive administration of perfusion solution. MATERIAL AND METHOD: 16 hypothermic experimental pig renal perfusion o 180 min completed under constant flow conditions. A vacuum computer-controlled pump was used. A comparison was performed of the results obtained by two groups of organs (forced perfusion pressure -I.B.- and soft perfusion pressure -I.S.). RESULTS: Even though perfusion flor did not offer significant differences among both groups at the end of the procedure, I.B. group showed medium perfusion pressure and renal vascular resistance values significantly higher. Nitric oxide metabolites concentration was also greater in I.B. group. Finally, these kidneys showed more tubular cell aedema and glomerular shrinkage in comparison to I.S. group. CONCLUSIONS: Sharp and forced hypothermic perfusion of the isolated kidney don't increase flow perfusion values. Inversely, hydrodynamic and pathologic results are worst in comparison to soft and progressive organ perfusion.

Hydrodynamic and biochemical effects of isolated hypothermic renal perfusion depending on the pump model and perfusion solution.

OBJECTIVES: To evaluate hydrodynamic, biochemical, and histological consequences of hypothermic isolated renal perfusion using a new computerized perfusion system. MATERIALS AND METHODS: The device that allowed us to obtain on renal hydrodynamics during perfusion included multiple parts. The organ was perfused at 4 degrees C with a constant flow either using a classic roller pump or a pump designed in our laboratory to employ vacuum or atmospheric pressure sequentially to achieve a truly pulsatile wave (vacuum-powered tubular pump). The study included 16 minipigs with Eurocollins or Belzer perfusion solutions sampled at predefined interval and histological studies of the organs performed. RESULTS: There was a significant difference in weight increase between the two types of pumps; those perfused with Eurocollins showed greater values than those with Belzer solution. Onset of nitric oxide (NO) in the perfusion solution increased inversely with the renal vascular resistance. The highest NO levels were observed with the Belzer solution and vacuum pump. CONCLUSIONS: Changes in renal hydrodynamics, as induced by perfusion wave form and solution type, may be recorded in real time using a computerized system. A vacuum pump with the Belzer solution achieved the best experimental results.

[Hydrodynamic and biochemical effects of hypothermic perfusion of isolated kidney according to the type of pump]. / Efectos hidrodinámicos y bioquímicos de la perfusión hipotérmica de riñón aislado según el tipo de bomba utilizada.

OBJECTIVE: To study on isolated kidney perfusions by means of a self-designed computer-controlled organ perfusion system the hydrodynamic and biochemical effects of two types of pumps: a self-designed vacuum powered tubular pump and a classical roller pump. BASIC PROCEDURES: Experimental study performed on 12 right mini-pig kidneys. After transperitoneal bilateral nephrectomy, organs are perfused with Eurocollins solution in a randomised manner with one type of pump. The system records continuously perfusion pressure, flow and renal resistance. RESULTS: Medium renal vascular resistance was significantly lower in vacuum powered tubular pump perfusions. LDH level in the solution showed correlation with perfusion flow. CONCLUSIONS: Vacuum powered tubular pump increases renal flow and lowers renal vascular resistance significantly in comparison to roller pump. LDH level in the solution is related to good-quality hydrodynamic perfusion parameter values.

[Computer-controlled isolated kidney hypothermic perfusion system]. / Sistema de perfusión hipotérmica de riñón aislado controlado por ordenador.

OBJECTIVE: To evaluate at the laboratory a self-designed computer-controlled kidney perfusion system. A vacuum powered tubular pump with active valves developed by our group is used. This pump is able to produce a flow and pressure patterns very similar to the pulse wave in the human circulatory system. BASIC PROCEDURES: This is an experimental study performed with mini-pig kidneys. After transperitoneal bilateral nephrectomy, both organs are sorted either to immediate perfusion or to perfusion after a period of 24 hours of cold storage in Eurocollins solution. The system is able to record continuously perfusion pressure, flow and intrarenal resistance. RESULTS: A progressive decrease in renal vascular resistance along with an increase in the flow value were observed during the procedures. These dynamic changes become evident both in immediate and deferred renal perfusions. CONCLUSIONS: Computer-controlled kidney perfusion system provide us the opportunity of recording in real time renal microcirculatory state modifications during a perfusion. Vascular system seems to be actively modified by the perfusion. This fact should be researched in the next future.