Noninvasive measurement of Carbon turnover for evaluation of porcine renal grafts during ex vivo machine perfusion.

Background: Kidney transplantation suffers from a shortage of donor organs. Despite this, a lot of grafts are discarded due to inadequate quality. As many kidneys are afflicted by transient filtration failure early after preservation, classical renal function tests are not applicable to differentiate between prospective recovery or continuing deficit of renal function.

Role of perfusion medium in rewarming machine perfusion from hypo- to normothermia.

Background: Gradual warming up of cold stored organ grafts using a controlled machine perfusion protocol facilitates restitution of cellular homeostasis and mitigates rewarming injury by adapted increase of temperature and metabolism. The aim of the present study was to compare intra- and extracellular type perfusion media for the use in machine perfusion-assisted rewarming from hypo- to normothermia.

Methods: Rat livers were retrieved 20 min after cardiac arrest.

Successful temporary machine perfusion of marginal liver grafts early after retrieval or shortly before implantation.

Objectives: The benefit of machine perfusion during storage of liver grafts retrieved after cardiac death should be investigated as applied either at the beginning or near the end of the preservation period.

Methods: Rat livers were explanted 20 min after cardiac arrest of the donor and cold-stored (CS) for 18 h. Other grafts were additionally subjected to 2 h of normothermic machine perfusion (MP) either 3 h after retrieval (early MP) or 3 h before reperfusion (late MP), thus extending total ischemic time to 20 h.

Comparison Between Terminal or Preterminal Conditioning of Donor Livers by Ex Situ Machine Perfusion.

Background: The successful implementation of end-ischemic normothermic machine perfusion (NMP) into clinical practice comes along with unusual demands for trained personnel and technical facilities in the implantation clinic. This creates an interest to bundle expertise and professional equipment for execution of MP at regional pump centers at the disadvantage of adding a second short period of cold preservation while sending the reconditioned grafts to the actual implant clinic. Differences of liver recovery upon reperfusion either immediately after NMP or after 3 h of cold storage subsequent to NMP should therefore be evaluated.

The impact of oxygen supply and erythrocytes during normothermic kidney perfusion.

The influence of erythrocytes and oxygen concentration on kidneys during long-term normothermic kidney perfusion is under debate. This study compares acellular and erythrocyte-based NMP with focus on oxygen delivery to the tissue as well as the effects of high oxygenation on tissue integrity. Pig kidneys were connected to NMP for six hours.

Controlled oxygenated rewarming as novel end-ischemic therapy for cold stored liver grafts. A randomized controlled trial.

Abrupt return to normothermia has been shown a genuine factor contributing to graft dysfunction after transplantation. This study tested the concept to mitigate reperfusion injury of liver grafts by gentle warming-up using ex vivo machine perfusion prior to reperfusion. In a single center randomized controlled study, livers were assigned to conventional static cold storage (SCS) alone or to SCS followed by 90 min of ex vivo machine perfusion including controlled oxygenated rewarming (COR) by gentle and protracted elevation of the perfusate temperature from 10°C to 20°C.

Comparison of thermal variations in post-retrieval graft conditioning on rat livers.

Background: Machine perfusion was found an effective tool to recover organ grafts from ischemic insults during preservation. It could be observed that organ integrity is significantly affected by abrupt temperature shifts during hypothermic storage and implantation periods. Studies showed that a gentle and controlled rise of the temperature during oxygenated machine perfusion prior to implantation can protect the tissue from reperfusion injury.

Effect of oxygen concentration in anterograde liver persufflation on high energy phosphates and graft function after ischemic preservation.

Here we evaluate the potential of anterograde gaseous oxygen persufflation for graft reconditioning after extended storage times. Pig livers were retrieved and cold-stored in HTK solution for 16 h. Some grafts were subsequently subjected to anterograde gaseous oxygen persufflation via the portal vein for 2 h.

Controlled Rewarming after Hypothermia: Adding a New Principle to Renal Preservation.

Early graft dysfunction due to preservation/reperfusion injury still represents a notable issue after kidney transplantation, affecting long term prognosis of graft viability. One trigger of postischemic cell dysfunction could be recognized in the abrupt temperature shift from hypo- to normothermia, leading to mitochondrial dysfunction and proapoptotic signal transduction. Here we propose a technique to cope with this "rewarming injury" by interposing a period of gentle warming up by hypo- to subnormothermic machine perfusion of the isolated graft prior to warm reperfusion.

Ex vivo use of a Rho-kinase inhibitor during renal preservation improves graft function upon reperfusion.

Background: Activation of the Rho-Rho-kinase pathway has been shown to cause vasoconstriction in renal afferent arterioles. Vascular dysfunction plays a pivotal role in triggering reperfusion injury after kidney transplantation. Therefore, the effect of a Rho-kinase inhibitor, added to the preservation solution, on renal function after 18 h of storage at 4 °C was evaluated.

Adding pulsatile vascular stimulation to venous systemic oxygen persufflation of liver grafts.

The effect of adding pulsatility to gaseous oxygen persufflation during liver preservation was studied in an isolated rat liver model. Livers from male Wistar rats were retrieved 30 min after cardiac arrest of the donor and subjected to 18 h of cold storage. Some grafts were subjected to nonpulsatile or pulsatile gaseous oxygen persufflation.

Role of pulsatility in hypothermic reconditioning of porcine kidney grafts by machine perfusion after cold storage.

Background: Brief in-house machine perfusion after cold storage (CS) (hypothermic reconditioning) has been proposed as a convenient tool to improve kidney graft function. The present study aimed to investigate the mechanistic role of vascular pulsatility in this context.

Methods: Kidney function after cold preservation (4°C, 18 hr) and subsequent reconditioning by 90 min of pulsatile machine perfusion (PP) (30/20 mm Hg) or nonpulsatile machine perfusion (NPP) (30 mm Hg) was studied in an isolated kidney perfusion model in pigs (n=6 for both) and compared with simply CS grafts.

Use of the new preservation solution Custodiol-N supplemented with dextran for hypothermic machine perfusion of the kidney.

Custodiol-N is a new preservation solution specifically designed to prevent free radical-induced tissue alterations and to protect vascular integrity of the graft. Thus, Custodiol-N appears particularly suitable as base solution for oxygenated machine preservation and its putative benefit for renal preservation by hypothermic machine perfusion (HMP) was investigated using a porcine in vitro model. Kidneys were retrieved from German Landrace pigs and preserved for 20 h by pulsatile oxygenated HMP on a Lifeport kidney transporter (syst.

Role of oxygenation in hypothermic machine perfusion of kidneys from heart beating donors.

Unlabelled: Dynamic preservation of organ grafts by hypothermic machine perfusion (HMP) has regained broader interest to provide better outcome after transplantation. One pivotal aspect still under debate is the role of oxygenation during HMP. The present study investigates functional and molecular aspects of active oxygenation during HMP of kidneys from heart beating donors.

Hypothermic reconditioning by gaseous oxygen persufflation after cold storage of porcine kidneys.

Background: Delayed graft function still represents a major complication in clinical kidney transplantation. Here we tested the possibility to improve functional outcome of cold stored kidneys a posteriori by hypothermic reconditioning using retrograde oxygen persufflation (ROP) immediately prior to reperfusion.

Methods: Kidneys from female German Landrace pigs were flushed with Histidine-Tryptophan-Ketoglutarate (HTK) solution and cold-stored for 18 h (control).

Energetic recovery in porcine grafts by minimally invasive liver oxygenation.

Background: Gaseous insufflation of oxygen via the venous vascular system has proven to be an effective tool for preventing anoxic tissue injury after extended time periods of ischemic liver preservation. Most experimental studies so far have been undertaken in rat models and include a series of pinpricks into postsinusoidal venules as an outlet for the insufflated gas. Here, we describe a simplified technique for minimally invasive liver oxygenation in porcine grafts, representing a hassle-free access to organ oxygenation without vascular lesions.

Hypothermic reconditioning of porcine kidney grafts by short-term preimplantation machine perfusion.

Background: Clinical trial data suggest that continuous hypothermic machine perfusion (HMP) during the entire preservation period reduces the incidence of delayed graft function and improves graft survival. This study evaluates whether short-term MP after cold storage (CS) is also effective.

Methods: Kidney function after cold preservation (4°C, 21 hr) and transplantation was studied in an autotransplant model using Landrace pigs (25-30 kg; n=5 per group) with 1 week follow-up.

Dopamine improves hypothermic machine preservation of the liver.

Background: Hypothermic machine preservation (HMP) is currently reconsidered as alternative to standard cold storage of organs from non-heart-beating donors. The present study was aimed at investigating the possible synergistic effect of HMP and the addition of dopamine to the circulating perfusate during preservation.

Methods: Cardiac arrest was induced in male Wistar rats (250-300 g) by phrenotomy.

Optimal time for hypothermic reconditioning of liver grafts by venous systemic oxygen persufflation in a large animal model.

Background: Quality of cold-stored livers declines beyond 12 hr of ischemia, increasing the risk of primary dysfunction. Here we evaluate the potential and optimal treatment interval of gaseous oxygen persufflation for grafts reconditioning after long storage times in an experimental pig liver model.

Method: Porcine livers (n=6/group) were cold stored at 4°C for 18 hr in histidine-tryptophan-ketoglutarate solution.

Role of oxygen during hypothermic machine perfusion preservation of the liver.

Grafts from non-heart-beating donors are thought to be best preserved by hypothermic machine perfusion (HMP). Controversy exists concerning the role of oxygenation during HMP. In this study, we wanted to evaluate the relative role of oxygenation for graft integrity during and after HMP.