Liver transplant: Reperfusion effect
Advanced, Clinical - Hepatic, Organ-Based and Clinical Sciences
Liver transplant surgery may be divided in to three stages: the preanhepatic (or dissection) stage, the anhepatic stage, and the neohepatic stage. Each stage yields specific anesthetic considerations. The preanhepatic stage begins with incision and ends with cross-clamping of the portal vein, the hepatic artery, and the inferior vena cava (IVC) or hepatic vein. The anhepatic stage then begins. Once the native liver is removed and the allograft is implanted, reperfusion of the graft by unclamping the portal vein signals the onset of the neohepatic stage. The neohepatic stage continues through the anastomosis of the hepatic artery, anastomosis of the bile duct and closure of the abdomen.
Reperfusion of the graft may be a time of significant hemodynamic instability. The opening of the portal vein allows for blood flow through the graft and the IVC clamp is released. Potassium and hydrogen ions that have built up in the graft during the ischemic period as well as from the preservation solution (i.e. University of Wisconsin solution) are released into systemic circulation. The blood through the graft is also cold, contains micro-thrombi and vasoactive substances. These factors all may contribute to causing profound hypotension and cardiac arrhythmias, including cardiac arrest. Close attention must be paid to the patient’s core temperature (measured centrally through a pulmonary artery catheter) as well as the patient’s electrocardiogram (EKG) during this period. Calcium chloride and sodium bicarbonate are used to treat hyperkalemia and low-dose epinephrine may be used to treat systemic hypotension. Patients who experience post-reperfusion syndrome (prolonged hypotension following reperfusion of the graft) may require vasopressor and/or inotropic support in order to maintain adequate perfusion during this period.