Early Acid–Base Balance Disorders During Kidney Transplantation

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.

Transplanted Kidney Increases Nitric Oxide Formation With Metabolic Acidosis Reduction

OBJECTIVES

As a vasodilator, nitric oxide is considered to play a significant role in the homeostatic regulation of renal hemodynamics. To test the hypothesis that a kidney graft is capable of producing nitric oxide immediately after renal transplant surgery, we examined the possibility that it positively affects local metabolic acidosis.

MATERIALS AND METHODS

In kidney transplant recipients, we analyzed renal vein and central vein blood samples, which reflect local and systemic metabolic alterations, respectively. Samples were taken immediately after kidney recirculation (that is, the first blood passing through after clamps are released) and at 5, 15, and 30 minutes thereafter. Levels of nitric oxide metabolites (nitrites, nitrates, and their sum), malondialdehyde (an indicator of oxidative damages), and parameters of acid-base balance (pH level, actual excess base, hemoglobin, actual bicarbonate, partial pressure of carbon dioxide, partial pressure of oxygen) were analyzed. Living kidney donors (the recipients' parents) were controls.

RESULTS

In renal vein samples, nitrates and the sum of nitrites and nitrates were significantly higher than that shown in control (P < .001) and central vein (P < .05) samples, suggesting an immediate increase in nitric oxide production in the transplanted organ. Metabolic acidosis occurred in both the renal and central vein, indicated by decreased pH and actual bicarbonate level as well as by negative actual base excess level. Only in the renal vein was an increased nitrite and nitrate associated with a reduction of negative actual excess base, thereby suggesting a decrease in anion formation.

CONCLUSIONS

Transplanted kidneys increase nitric oxide production immediately after organ transplant surgery, which positively affects local metabolic acidosis. The mechanism for this effect is likely local circulation improvement.

Acid-Base Balance Disorders During Kidney Preservation in Cold Ischemia

BACKGROUND

Acid-base balance disorders are a crucial element of ischemia-reperfusion injury during organ transplantation. Hypoxia during organ procurement and storage cause cellular homeostasis imbalance with impact on further graft function. Acidosis in preserved kidney caused by lactate accumulation may have an important role as a common denominator of various pathways leading to cellular damage.

METHODS

Our trial sought to answer questions regarding a range of pH alterations in the kidney before the transplantation, their potential cause, and how this may affect further outcome of the kidney transplantation procedure. Perfusion fluid for pH analysis was obtained from perfusion pump (PP) or through kidney flushing at the end of preservation depending on the storage method.

RESULTS

A total of 66 sample results were collated with the data from the transplant registry, hospitalization, and outpatient department. Statistical analysis was conducted linking pH results with factors related to donor, recipient, preservation, and outcome according to designed schematics. Mean perfusate pH was significantly lower in simple hypothermia (SH) vs the PP storage group (6.77 vs 7.11; P < .001). All samples of perfusate pH in the SH group were below physiological values (<7.35), and in 10% of samples in the SH group, pH >7.00.

CONCLUSIONS

We concluded that kidney storage in cold ischemia is associated with organ acidosis independent of preservation method and that SH is correlated with significantly bigger acidosis than storage in PP, which is an important procedure removing an excessive amount of hydrogen ions from kidney microcirculation, decreasing cell damage.

Isquemia e reperfusão por circulação retrógrada: estudo comparativo experimental

Resumo Contexto Isquemia crítica de membro inferior sem leito distal tem opções restritas para tratamento. Desviar o fluxo de maneira retrógrada através da circulação venosa é alternativa amparada em evidências de inúmeros trabalhos publicados. Objetivos Comparar o comportamento de variáveis clínicas e laboratoriais em extremidades de suínos submetidas a isquemia e a isquemia com reperfusão por circulação retrógrada entre si e em relação e a um grupo controle. Métodos Dez suínos foram separados em dois grupos. No grupo 1 (n=5), controle, avaliaram-se padrões fisiológicos de variáveis como fluxo ao Doppler, temperatura, gasometria, lactato, creatinoquinase (CK) e pressão arterial. No grupo 2 (n=5), após um período médio de isquemia de 27 minutos e 30 segundos, consequente à interrupção do fluxo nas artérias femorais, os animais foram submetidos a arterialização venosa no membro posterior esquerdo e a manutenção da isquemia no direito. As variáveis foram analisadas separadamente durante momentos 0, 2, 3, 4 e 6 horas após a reperfusão para efeito de comparação entre si e com o grupo controle. Resultados A análise das variáveis mostrou, em ambos os procedimentos, queda de BE e pO2, com elevação significativa de lactato e CK em relação ao grupo controle. Nos membros isquêmicos arterializados, encontramos fluxo ao Doppler e maiores pressões arteriais e temperaturas quando comparadas ao membro em isquemia. Conclusões A análise comparativa das extremidades em isquemia e isquemia arterializada mostrou, em relação ao grupo controle, um quadro de acidose metabólica, com significativo aumento de lactato e CK, que sugerem dano celular e sinais de reperfusão retrógrada nas extremidades arterializadas.

Influence of Perioperational Acid-Base Balance Disorders on Early Graft Function in Kidney Transplantation

INTRODUCTION

Reperfusion is a crucial moment in kidney transplantation, connected with many metabolic changes that are the result of preservation and intraoperative course including ion movements, free radical generation, ATP and other adenylate depletion. During reperfusion we observed increased metabolic acidosis, which may be the result of accumulation of lactic acid due to anaerobic metabolism, with a simultaneous expiratory pCO(2) growth as respiratory compensation. The study's purpose was to examine acid-base balance dynamics during 30 minutes of reperfusion of the transplanted kidney and its influence on renal function based on observations of the 1-year creatinine values.

MATERIALS AND METHODS

The examined group consisted of 76 recipients: 44 men, 32 women. Measurements by gasometric analysis and expiratory pCO(2) in each patient were performed nine times during reperfusion. In the postoperative period we analyzed donor-related factors including: gender, age, number of HLA matches weight and height, as well as recipient-related factors including: gender, age, basic immunosuppression, creatinine level at hospital discharge and at 5 to 24 months of follow-up. Statistical significance was analyzed using repeated-measures analysis of variance followed by Tukey post hoc test as well as Mann-Whitney U and Spearman's correlation tests.

RESULTS

The analysis showed correlations between reperfusion, acidosis, respiratory pCO(2) compensation, early graft loss, patient death, donor and recipient gender, renal function, donor age, and histocompatibility.

CONCLUSIONS

At the beginning of reperfusion there is increasing metabolic acidosis with simultaneous expiratory pCO(2) as compensation. A greater relative increase in expiratory air pCO(2) was correlated with a higher incidence of early graft loss. The higher intensity of metabolic acidosis correlated with worse renal function at 6 months after transplantation. Elderly donor age and fewer HLA-matched antigens correlated with greater intensity of metabolic acidosis during 30 minutes of kidney reperfusion.