Acid-Base Balance Disorders During Kidney Preservation in Cold Ischemia

Metabolic and Microcirculatory Changes in Severe Renal Ischemia-Reperfusion and Ischemic Preconditioning in the Rat: Are They Detectable in the First Hour of Reperfusion?

Ischemia-reperfusion (I/R) strongly affects a graft's function and survival and modulates microcirculatory and hemorheological parameters. However, the boundary between the reversibility and irreversibility of damage is unclear. This study compared the effects of renal I/R and ischemic preconditioning (IPC) to determine whether metabolic, microcirculatory, and micro-rheological changes are already detectable in the first hour of reperfusion. Wistar rats were divided into control (n = 6), I/R (n = 7) and IPC (n = 7) groups. In the ischemic groups the left kidney was subjected to 120 min of ischemia followed by 60 min of reperfusion. In the IPC group, a 3 × 5 min protocol was used prior to the manifest ischemia. Parenchymal microcirculation and renal artery blood flow were measured before ischemia (base) and during reperfusion (R-30, R-60). Hematological, micro-rheological parameters, electrolytes, and metabolites were tested at base and at R-60. Both ischemic groups showed micro-rheological impairment. An increase in potassium, lactate, and creatinine concentrations and a decrease in pH were observed. The blood flow of the IPC group deteriorated less, and microcirculation recordings indicated better values. The 120 min ischemia and the 60 min reperfusion resulted in micro-rheological and metabolic alterations, together with decreased renal blood flow and parenchymal microcirculation. Although the applied IPC protocol showed minor protective effects, its impact was limited in the first hour of reperfusion.

A Review of Current and Emerging Trends in Donor Graft-Quality Assessment Techniques

The number of patients placed on kidney transplant waiting lists is rapidly increasing, resulting in a growing gap between organ demand and the availability of kidneys for transplantation. This organ shortage has forced medical professionals to utilize marginal kidneys from expanded criteria donors (ECD) to broaden the donor pool and shorten wait times for patients with end-stage renal disease. However, recipients of ECD kidney grafts tend to have worse outcomes compared to those receiving organs from standard criteria donors (SCD), specifically increased risks of delayed graft function (DGF) and primary nonfunction incidence. Thus, representative methods for graft-quality assessment are strongly needed, especially for ECDs. Currently, graft-quality evaluation is limited to interpreting the donor’s recent laboratory tests, clinical risk scores, the visual evaluation of the organ, and, in some cases, a biopsy and perfusion parameters. The last few years have seen the emergence of many new technologies designed to examine organ function, including new imaging techniques, transcriptomics, genomics, proteomics, metabolomics, lipidomics, and new solutions in organ perfusion, which has enabled a deeper understanding of the complex mechanisms associated with ischemia-reperfusion injury (IRI), inflammatory process, and graft rejection. This review summarizes and assesses the strengths and weaknesses of current conventional diagnostic methods and a wide range of new potential strategies (from the last five years) with respect to donor graft-quality assessment, the identification of IRI, perfusion control, and the prediction of DGF.

Advances in Hypothermic and Normothermic Perfusion in Kidney Transplantation

Hypothermic and normothermic machine perfusion in kidney transplantation are purported to exert a beneficial effect on post-transplant outcomes compared to the traditionally used method of static cold storage. Kidney perfusion techniques provide a window for organ reconditioning and quality assessment. However, how best to deliver these preservation methods or improve organ quality has not yet been conclusively defined. This review summarises the promising advances in machine perfusion science in recent years, which have the potential to further improve early graft function and prolong graft survival.

Assessment of Oxidative Stress Markers in Hypothermic Preservation of Transplanted Kidneys

Ischemia-reperfusion injury (IRI) after renal transplantation is a complex biochemical process. The first component is an ischemic phase during kidney storage. The second is reperfusion, the main source of oxidative stress. This study aimed to analyze the activity of enzymes and concentrations of non-enzymatic compounds involved in the antioxidant defense mechanisms: glutathione (GSH), glutathione peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione transferase (GST), thiobarbituric acid reactive substances (TBARS), malondialdehyde (MDA), measured in preservation fluid before transplantation of human kidneys (KTx) grafted from brain dead donors. The study group (N = 66) was divided according to the method of kidney storage: Group 1—hypothermic machine perfusion (HMP) in LifePort perfusion pump, n1 = 26, and Group 2—static cold storage (SCS), n2 = 40. The measurements of kidney function parameters, blood count, and adverse events were performed at constant time points during 7-day hospitalization and 3-month follow-up. Kidney perfusate in Group 2 was characterized by significantly more acidic pH (p < 0.0001), higher activity of GPX [U/mgHb] (p < 0.05) and higher concentration of MDA [μmol/L] (p < 0.05). There was a statistically significant improvement of kidney function and specific blood count alterations concerning storage method in repeated measures. There were aggregations of significant correlations (p < 0.05) between kidney function parameters after KTx and oxidative stress markers: diuresis & CAT, Na⁺ & CAT, K⁺ & GPX, urea & GR. There were aggregations of significant correlations (p < 0.05) between recipient blood count and oxidative stress markers: CAT & MON, SOD & WBC, SOD & MON. Study groups demonstrated differences concerning the method of kidney storage. A significant role of recipient’s gender, gender matching, preservation solution, and perfusate pH was not confirmed, however, basing on analyzed data, the well-established long-term beneficial impact of HMP on the outcome of transplanted kidneys might partially depend on the intensity of IRI ischemic phase and oxidative stress, reflected by the examined biomarkers.