MELD predictive value of alterations of brain perfusion during liver transplantation

INTRODUCTION: The systemic circulation of patients with liver failure is characterized by low vascular resistance and a compensatorily increased cardiac output. In addition, some patients show functional loss of the autoregulation system for cerebral blood flow, creating enhanced risk during orthotopic liver transplantation (OLT), a possible cause of the high incidence of central nervous system complications after OLT. PATIENTS AND METHODS: Sixteen consecutive patients undergoing OLT were enrolled and characterized by the Child-Pugh (CTP), the MELD, and the HCC-adjusted-MELD score before surgery. OLT was performed with the "piggyback" technique. Brain perfusion and oxygenation was monitored by NIRO300 by Hamamatsu. This instrument detects concentration changes in oxygenated hemoglobin (DeltaHbO(2)), deoxygenated hemoglobin (DeltaHHb), and total volume of hemoglobin (DeltaHbT). It also calculates the tissue oxygenation index (TOI), namely HbO(2)/HbT expressed as a percentage, and the tissue hemoglobin index (THI). RESULTS: The lowest levels of brain perfusion were recorded at the washout, DeltaHbO(2) = -13.95 (-20/-5.3) micromol L(-1) and TOI = 51.5 (35.2/70.7)%, while immediately after, at reperfusion, the highest peaks were observed: DeltaHbO(2) was 0.16 (16.9/13) micromol L(-1); DeltaHbT was 1.1 (22.3/11.8) mumol L(-1); and TOI was 73.6 (78.1/65.3)%. CONCLUSIONS: Patients with more severe liver deficiency scores showed higher levels of brain perfusion and oxygenation during surgery. Both the MELD and the CTP score predict alterations in brain perfusion.