Effect of graft size, recipient's age and intra-operative cerebral oxygen saturation on liver transplant outcomes in Hong Kong

Abstract

Liver transplantation is a life-saving procedure for patients with end stage liver disease or unresectable hepatocellular carcinoma. The surgery is associated with a mortality rate of 10% and complication rate of 30%; this together with the severe organ shortage in our locality warrants the need to optimise recipient selection criteria and to explore means to increase graft supply. A method of expanding donor pool that has been extensively investigated is the adoption of small-for-size grafts (SFSG) defined as graft-to-recipient weight ratio of <0.8%. A meta-analysis investigating the impact of SFSG on medium- and long-term graft survival showed inferior 3-year graft survival in the SFSG group but similar 5-year graft survival. This result was comparable with analysis of local data which also did not demonstrate inferior long-term survival in patients receiving SFSG. These provide evidence to support the expansion of donor pool by adopting small-for-size grafts in living donor liver transplantation. In view of scarcity of organ supply, optimisation of patient selection criteria is of utmost importance. The median age of patients requiring liver transplantation is expected to increase with the ageing population. A retrospective analysis on the effect of recipient age on postoperative patient survival in this locality demonstrated that patients >65 years old has statistically significant inferior survival when compared with younger patients. Multivariate analysis identified preoperative hepatorenal syndrome type acute kidney injury (HRS-AKI) as a major risk factor of worse survival in this group. After exclusion of older patients with preoperative HRS-AKI, the difference in long term survival between the older and younger patients was no longer significant. This analysis suggests that age alone should not preclude liver transplantation. Post-operative neurological complications are associated with poor quality of life in liver transplantation recipients. Cerebral hypoperfusion has been identified as a risk factor of postoperative cognitive impairment. A randomised controlled trial was performed to investigate the effectiveness of intraoperative cerebral oxygen saturation (rScO2) monitoring and maintenance by anaesthetic interventions in reducing the incidence of postoperative neurological sequelae. In this study, no difference in incidence of postoperative neurological complications was found between the intervention and control group. Preoperative total bilirubin and haemoglobin level was found to be independently associated with preoperative regional cerebral oxygen desaturation. These findings echoed that of previous studies that identified high preoperative bilirubin as an interference of cerebral oxygen saturation reading. The degree of cerebral oxygen desaturation as reflected by the area under curve was found to be associated with postoperative cognitive impairment. This may suggest a potential role of cerebral oximetry in liver transplantations as a predictor for postoperative cognitive impairment that might direct preventive and therapeutic management. Nonetheless, the result of the current study does not support the routine use of cerebral oximetry in liver transplantation surgery.