OXYGEN-CONSUMPTION, LACTATE METABOLISM, AND GASTRIC INTRAMUCOSAL PH IN AN EXPERIMENTAL LIVER-TRANSPLANTATION MODEL

Objective: To assess the usefulness of measuring whole-body oxygen con sumption ((V) over dot O-2), arterial lactate concentration, and gastr ic intramucosal pH (pHi) as parameters for evaluating hepatic graft vi ability in a model of experimental liver transplantation. Design: Expe rimental, prospective study. Setting: Hospital laboratory for experime ntal surgery. Subjects: Twenty-eight Landrace-Largewhite pigs: 14 dono rs and 14 recipients. Interventions: Orthotopic liver transplantation. Two groups were differentiated by graft preservation status: an optim al-graft group (group 1), which received donor livers that had been pr eserved in Collins solution at 4 degrees C for <4 hrs (n = 7), and an injured-graft group (group 2), which received donor livers that had be en preserved in Collins solution at 4 degrees C for >24 hrs (0 = 7). M easurements and Main Results: Hemodynamic parameters, variables relate d with systemic and hepatic oxygen and lactate metabolism, gastric pHi , and arterial pH were measured at two stages: a) preanhepatic stage; and b) neohepatic stage (60 mins after reperfusion). There were no dif ferences in (V) over dot O-2 between graft groups or stages. In the ne ohepatic stage, hepatic oxygen extraction and lactate turnover were si gnificantly higher in the optimal-graft group than in the injured-graf t group. In the neohepatic stage, gastric pHi decreased significantly and arterial lactate concentrations increased significantly in both gr oups. Conclusions: Changes in hepatic (V) over dot O-2, cannot be dete cted by (V) over dot O-2 measurements. Optimal-state grafts increased their lactate turnover as a result of substrate overload, but injured grafts did not Therefore, the evolution of arterial lactate concentrat ions in the immediate postoperative period may be useful for the early evaluation of transplanted livers. Gastric pHi can be a useful measur ement in the immediate posttransplantation period for differentiating between hyperlactacidemia produced by liver dysfunction (normal pHi) a nd hyperlactacidemia produced by lactate generation as a consequence o f inadequate tissue oxygenation or of a mixed origin (abnormal pHi).