Vasoconstrictor use in liver transplantation: is there evidence for rational use?

Liver transplantation is a challenging surgical operation performed in recipients with major hemodynamic perturbations related to portal hypertension. The pathophysiologic alterations in portal hypertension include a hyperdynamic circulation and decline in systemic vascular resistance and mean arterial pressure. Cardiac function can also be depressed due to cirrhosis related cardiomyopathy. These cirrhosis related changes often lead to a tenuous state in which organ perfusion is threatened and declines rapidly in the setting of many other insults including blood loss, infection, and use of medications which can cause a decline in blood pressure. This can result in renal failure as well as reduced perfusion of other organs. Additionally, direct consequences of portal hypertension include risk of bleeding from porto-systemic collaterals both in the gastrointestinal tract as well as during abdominal dissection in liver transplantation. In this milieu the management of hemodynamic alterations during liver transplant surgery is a daunting task. Recent approaches have utilized various vasoconstrictor therapies along with judicious use of intravenous fluids to maintain systemic pressures and organ perfusion. Added advantages of this approach include the potential for reducing portal pressure and thus the severity of intra-abdominal hemorrhage during surgery as well as potentially increasing renal blood flow and reducing mesenteric hyperemia. Avoidance of liberal fluid use to maintain systemic pressures also has the advantage of reducing the severity of pulmonary edema and risk of reintubation or prolonged intubation after surgery. Although these approaches utilizing vasoconstrictors are promising, many questions remain. Randomized controlled trials like those performed in the pretransplant population are sparse in the setting of liver transplantation. The optimal vasoconstrictors including combinations and doses have not been defined. Most of the benefits demonstrated thus far have been surrogate outcomes such as reduced transfusion requirement, decreased need for reintubation and improved systemic hemodynamics and reduced portal pressures during surgery. There may be different outcomes of these approaches in patients with varying severities of liver disease. The safety of minimization of fluids, along with vasoconstrictor therapy during liver transplantation has been questioned in patients with higher risk of renal failure including recipients with high MELD scores. Other factors besides disease severity, including organ quality and cold ischemia times, need to be accounted for in future trials. Optimal outcomes including postoperative patient and graft survival, hospital stay and renal function should also be incorporated in future trials of vasoconstrictor therapy during liver transplantation.