The Effect of Norepinephrine on Blood Volume Cardiac , Output and Systemic Filling Pressure in Patients Undergoing Liver Transplant .

The derangement of circulatory blood volume in patients with liver cirrhosis makes intraoperative fluid management during liver transplant is challenging . Cirrhotic patients not only have large blood volume but abnormal blood volume distribution, with a substantial fraction of this volume in the splanchnic circulation (. These hemodynamic changes render volume loading in these patients has little impact on CO because a large proportion of infused fluid is shifted to the splanchnic system . In addition, patients with liver cirrhosis is similar to septic patients who have increased total vascular compliance which may cause pooling of blood in venous pool. Several studies in patients with sepsis found that use of low dose vasopressor may convert unstressed blood volume (i.e the amount of blood not causing pressure on the vessels) to stressed volume (i.e additional blood causing a distending pressure on the vascular walls and reflects the effective circulating volume) . However, no previous studies tested the effect of using norepinephrine (NE) on venous return and cardiac preload in patients undergoing liver transplant. An obvious advantage of this possibility is that NE will be used instead of true fluid replacement which may minimize fluid replacement during operation.

Recently, a method was described to estimate the changes in intravascular volume and vascular capacitance by calculating mean systemic filling pressure (MSFP) . MSFP is the driving pressure in venous return, and it allows calculation of the arterial and venous components of systemic vascular resistance .