Considerations for anesthetic manasgement during veno-venous bypass in adult hepatic transplantation

Intraoperative data from 42 adult orthotopic hepatic transplant recipients were analyzed retrospectively to assess the hemodynamic, coagulation, and thermal effects of heparinless veno-venous bypass using a constrained vortex pump. Transient hemodynamic changes occurring at the onset of bypass included decreases in temperature (-10.7%), heart rate (-18.7%) and arterial pressure (-15.1%); and increases in central venous pressure (27.6%) and ECG T wave amplitude (231.6%). Abrupt decreases in cardiac output and pump flow occurred with termination of the portal limb of bypass, which is required to allow completion of the portal vein anastomosis. However, significant continuous decreases were observed in bypass flow and cardiac output during the entire bypass period. The blood volume became concentrated as indicated by increases in hematocrit, colloid osmotic pressure, serum osmolality and serum sodium. Changes in colloid osmotic pressure were inversely related to bypass flow. These data, along with an accumulating base deficit, suggest that veno-venous bypass is associated with less than optimal perfusion of the abdomen and lower extremities. Flow dependent third space fluid accumulation is most likely responsible for decreasing cardiac output and pump flow during the bypass period. No clinically significant coagulopathy could be attributed to the use of veno-venous bypass. There were no significant changes in platelet counts, fibrinogen levels or prothrombin times. The activated partial thromboplastin time decreased from 60.5 to 50.2 seconds. Patient core temperature decreased three times more rapidly (0.9°C/hr) during bypass than at any other time during the procedure.