The Assessment of Change in Total Oxygenation by Continuous Monitoring of Mixed Venous Oxygen Saturation during Canine Orthotopic Liver Transplantation

Woo, Sung; Kim, Moon Cheol; Cho, Kang Hee; Paik, Kye Hyung; Wang, Hee Jung; Lee, Hyug Sang

Abstract

There are many hemodynamic and physiologic changes during liver transplantation much more than other surgical interventions. The oxygen delivery and oxygen consumption are af- fected by depressed hemodynamic and metabolic status during the operation. At the lower levels of oxygen present in venous blood, a linear relationship exists between saturation and tension. The use of fiberoptic oximetry system in conventional pulmonary artery flotation catheters has made the bedside application of this relationship of practical value in the continuous assessment of mixed venous oxygen saturation. This study was performed to determine changes in SvO2 and other variables of oxygen kinetics during canine OLT and study the correlation between SvO2 and cardiac output, SvO2 and oxygen consumption and oxygen utilization ratio. The continuous rnixed venous oxygen saturation and cardiac output by SO2/CO computer were monitored and the oxygen delivery, oxygen consumption and oxygen utilization ratio were calculated by arterial and venous blood gas analysis and modified Fick's equation during orthotopic liver transplantation in 20 dogs. The results were as follow as ; 1. There was no significant difference in tissue oxygen extraction between preoperative control and anhepatic phase, while cardiac output were decreased during anhepatic phase. 2. By utilizing centrifugal pump(venovenous bypass) oxygen delivery and oxygen utilization ratio were well maintained even though suppressed the change of oxygen delivery and oxygen consumption during anhepatic phase. 3. There was a significant decrease in SvO2 immediately after declamping the suprahepatic vena cava, whereas the oxygen utilization rate and oxygen consumption following reperfusion were significantly increased than just prior to reperfusion of transplanted liver. 4. A Statistically significant correlation was found between SvO2 and cardiac output, oxygen consumption in all surgical stages except reperfusion(CO;r=0.478, p<0.001, VO2,r=-0. 272, p=0.004), but their correlations were relatively poor. However, there was highly significant correlation among SvO2 and oxygen utilization ratio in all surgical stages(O2UR; r=- 0.834, P<0.001). In conclusion, continuous monitoring mixed venous oxygen via a fiberoptic pulmonary catheter could be used as the index for evaluation of hemodynamics and oxygen kinetics during canine OLT, but further research should be performed to determine whether these measurements indicate viability of the grafted liver.