Presence of a nitric oxide synthase inhibitor in the graft efflux during reperfusion in human liver transplantation

Protective Role of Hepatocyte Cyclooxygenase-2 Expression Against Liver Ischemia-Reperfusion Injury in Mice

Liver ischemia and reperfusion injury (IRI) remains a serious clinical problem affecting liver transplantation outcomes. IRI causes up to 10% of early organ failure and predisposes to chronic rejection. Cyclooxygenase-2 (COX-2) is involved in different liver diseases, but the significance of COX-2 in IRI is a matter of controversy. This study was designed to elucidate the role of COX-2 induction in hepatocytes against liver IRI. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were subjected to IRI. hCOX-2-Tg mice exhibited lower grades of necrosis and inflammation than Wt mice, in part by reduced hepatic recruitment and infiltration of neutrophils, with a concomitant decrease in serum levels of proinflammatory cytokines. Moreover, hCOX-2-Tg mice showed a significant attenuation of the IRI-induced increase in oxidative stress and hepatic apoptosis, an increase in autophagic flux, and a decrease in endoplasmic reticulum stress compared to Wt mice. Interestingly, ischemic preconditioning of Wt mice resembles the beneficial effects observed in hCOX-2-Tg mice against IRI due to a preconditioning-derived increase in endogenous COX-2, which is mainly localized in hepatocytes. Furthermore, measurement of prostaglandin E2 (PGE2 ) levels in plasma from patients who underwent liver transplantation revealed a significantly positive correlation of PGE2 levels and graft function and an inverse correlation with the time of ischemia. Conclusion: These data support the view of a protective effect of hepatic COX-2 induction and the consequent rise of derived prostaglandins against IRI.

Postreperfusion hyperkalemia in liver transplantation using donation after cardiac death grafts with pathological changes

BACKGROUND

With the increasing use of donation after cardiac death (DCD), especially of the graft liver with steatosis or other pathological changes, the frequency of postreperfusion hyperkalemia in liver transplantation has increased significantly. The present study aimed to determine the factors associated with developing postreperfusion hyperkalemia in liver transplantation from DCD.

METHODS

One hundred thirty-one consecutive adult patients who underwent orthotopic liver transplantation from DCD were retrospectively studied. Based on serum potassium within 5 minutes after reperfusion, recipients were divided into two groups: hyperkalemia and normokalemia. According to preoperative biopsy results, the DCD graft livers were classified into five categories. Univariate analysis was performed using Chi-square test to identify variables that were significantly different between two groups. Multivariate logistic regression was used to confirm the risk factors of developing hyperkalemia and postreperfusion syndrome. Correlation analysis was used to identify the relationship between the serum concentration of potassium within 5 minutes after reperfusion and the difference in mean arterial pressure values before and within 5 minutes after reperfusion.

RESULTS

Twenty-two of 131 liver recipients had hyperkalemia episodes within 5 minutes after reperfusion. The rate of hyperkalemia was significantly higher in recipients of macrosteatotic DCD graft liver (78.6%, P<0.001) than that in recipients of non-macrosteatotic DCD graft liver. The odds ratio of developing postreperfusion hyperkalemia in recipients of macrosteatotic DCD graft liver was 51.3 (P<0.001). Macrosteatosis in the DCD graft liver was an independent risk factor of developing hyperkalemia within 5 minutes after reperfusion. The highest rate of postreperfusion syndrome also occurred in the recipients with macrosteatotic DCD graft liver (71.4%, P<0.001). A strong relationship existed between the serum potassium within 5 minutes after reperfusion and the difference in mean arterial pressure values before and within 5 minutes after reperfusion in macrosteatotic DCD graft liver recipients.

CONCLUSION

Macrosteatosis in the DCD graft liver was an independent risk factor of developing hyperkalemia and postreperfusion syndrome in the recipients.

Nafamostat mesilate attenuates Postreperfusion Syndrome during liver transplantation

Postreperfusion syndrome (PRS), an acute decrease in blood pressure after reperfusion of the liver graft, occurs frequently during liver transplantation surgery. We supposed that the activation of the kallikrein-kinin system leading to extensive systemic vasodilatation was a possible cause. The effect of pretreatment with nafamostat mesilate (NM), a broad spectrum serine protease inhibitor, on the occurrence of PRS was evaluated. Sixty-two adult liver recipients were randomized to receive an intravenous bolus of either 0.02 mg/kg of NM (NM group, n = 31) or an equal volume of normal saline (control group, n = 31) just before reperfusion of the liver graft. Occurrence of PRS and intraoperative use of vasoactive drugs were compared between the two groups. Postoperative recovery was also compared. PRS was significantly less frequent (48% vs. 81%, p = 0.016) requiring less vasopressors in the NM group compared to the control group. The NM group also showed faster recovery of the mean arterial pressure. Perioperative laboratory values were similar between the two groups. Pretreatment with 0.02 mg/kg of NM immediately before reperfusion decreases the frequency of PRS and vasopressor requirements during the reperfusion period in liver transplantation.

Reperfusion injury in liver transplantation

Reperfusion injury occurring in the transplanted liver is a complex lesion and has been the focus of considerable research over the past decade. This section will review recent major developments in understanding the mechanisms involved and their application to clinical transplantation.

Presence of methylated arginine derivatives in orthotopic human liver transplantation: relevance for liver function

Orthotopic liver transplantation (OLT) is a frequent option in the treatment of liver diseases. During the cold ischemia period of the donor liver, there is an accumulation of metabolites that are potent inhibitors of the cytokine-inducible and endothelial nitric oxide synthase isoenzymes. We identified the presence of L-N-monomethylarginine and asymmetric dimethylarginine (ADMA) as the main inhibitors by means of analytic high-pressure liquid chromatography and mass spectrometry techniques. An average ADMA concentration of 450 micromol/L was measured in the preservation medium of donor livers with poor outcomes after OLT. A statistically significant relationship was observed between the concentration of methylated arginine derivatives in the graft and liver function after OLT. These data suggest that measurement of methylated arginine, released after liver protein catabolism, might provide an indication of functional status of the liver that can help the development of strategies intended to improve graft viability.