[Intraoperative oxygen consumption and organ function in liver transplantation]

Liver transplantation has become established as a reasonable and promising treatment option in terminal stages of liver diseases. Since there is no permanent artificial liver support available, primary "non-function" (PNF) of the graft is one of the most threatening complications. Therefore, an early and, if possible, intraoperative assessment of liver function is essential. Pathological changes in total oxygen consumption (VO2) are considered as an early indicator for the occurrence of PNF. Previously, PNF was analyzed using extensive calculations according to the Fick method, but since inauguration of the PhysioFlex anaesthesia device (Dräger, Lübeck, Germany), which is based on a closed anaesthesia circuit, continuous monitoring of oxygen consumption has become possible. The aim of the study was to investigate whether continuous VO2 monitoring using PhysioFlex allows immediate detection of pathological changes in graft function in the very early neohepatic phase of liver tranplantation. Therefore, 51 liver transplants were investigated at the University Hospital of Magdeburg with regard to a correlation between intraoperative VO2 values and ischaemic time periods of the donor organ and the postoperative liver function. A regular course of oxygen consumption was found in uncomplicated transplants and prompt liver function within normal ranges. PNF was not observed in any transplants. Changes in oxygen consumption were caused by early retransplants or by the delayed start of graft-based metabolism intraoperatively and transient diminished liver function found postoperatively, e.g., in pre-existing hepatorenal syndrome. In addition, VO2 indicated precisely the anhepatic and neohepatic phases during the course of liver transplantation. There was no correlation between the course of glucose content of the blood and the metabolic index of glucose and oxygen consumption or between both parameters and initial graft function. Furthermore, the duration of ischaemic time periods was not closely associated with oxygen consumption during the reperfusion phase. However, there was a correlation between intraoperative VO2 and postoperative bilirubin values, while a correlation between VO2 and GLDH as a further relevant parameter of postoperative graft function could not be confirmed, most likely because of the great variance in these values. In conclusion, the results suggest that changes in total oxygen consumption may, in part, be caused by changes in liver metabolism, depending on the various phases of liver transplantation. In addition, oxygen analysis allows monitoring of the critical phases of liver transplantation such as the anhepatic and early neohepatic periods with regard to immediate detection of early changes in graft metabolism. For routine use of this parameter, steady measurement of the mean value displayed on the PhysioFlex for selectable time periods would be helpful in addition to the continuous VO2 analysis, since there is a greater variance in the single VO2 values, which are documented by the anaesthesiologist, than in the online-detected and automatically calculated values of specific periods of transplantation.