Oxygen availability during orthotopic liver transplantation

Abstract

Studies have stressed the role of adequate tissue oxygenation in the light of an optimal patient outcome and allograft viability in liver transplantation. The practice of monitoring conventional hemodynamic parameters during liver transplantation could be complemented by parameters assessing real oxygen availability. In the present prospective study, real arterial available oxygen content (CavlO2) and its extraction ratio (O2ERavl) were calculated. These parameters include the effect of changes in oxyhemoglobin dissociation curve (ODC; expressed by P50) on oxygen availability, under the different circumstances occurring during liver transplantation. Sixteen adult cirrhotic patients were studied during orthotopic liver transplantation with the use of venovenous bypass. Classic hemodynamic measurements using a Swan-Ganz thermodilution catheter and arterial and mixed venous blood gas analysis were performed, and P50, oxygen delivery index (DO2ind), oxygen consumption index (VO2ind), oxygen extraction ratio (O2ER), CavlO2, and O2ERavl were calculated. Statistical analysis was performed using ANOVA for repeated measures and Spearman correlation coefficient matrix among the six variables (DO2ind, VO2ind, O2ER, P50, CavlO2, and O2ERavl) taken two at a time at every phase. Parameter P50 changed from 25.98 ± 1.10 to 23.15 ± 2.24 (at the end of operation). A leftward shift of the ODC was observed. The results showed positive association between P50 and CavlO2 after the removal of the native liver, and a weak and inconsistent relation of DO2ind with any of the other study variables. The intraoperative changes in P50 values, which represent a shift of the ODC to the left, may reflect a more accurate estimation of O2 release to the tissues, than the hemoglobin, PaO2 and SaO2 alone. Besides conventional hemodynamic parameters, P50, which includes the effect of alterations in ODC on oxygen availability, could be of value in monitoring the systemic oxygenation during liver transplantation.