Assesment of perioperative hemorheological parameters in liver transplant patients

Liver transplant is a life-saving treatment method. The liver is very important in the synthesis of coagulation factors and proteins. In chronic liver disease, lipids and proteins which are components of blood, and hematological parameters, are known to change. Therefore, in severe liver dysfunction, blood flow abnormalities are also seen. These abnormalities determine the flow characteristics of blood in large vessels and microvascular sections. Rheology is the science that studies the fluidity properties of a liquid. The concept of 'hemorheology' covers the fluid properties of the blood. Hemorheological parameters such as erythrocyte aggregation, deformability, blood and plasma viscosity have not been investigated during or after liver transplantations. The aim of this study was to investigate the hemorheological properties altering blood fluidity and effective tissue perfusion at intraoperative and postoperative period for improving graft functions and to assume the influence of hemorheology and factors affecting blood rheology on the success of future liver transplantations. The study was carried out between March 2019 and January 2020 at operating rooms and Intensive Care Clinics of Akdeniz University Faculty of Medicine. Seventeen patients older than 18 years who underwent liver transplantation were included. The study was carried out with the permission of Akdeniz University Faculty of Medicine Clinical Researches Local Ethics Committee. Blood samples were taken from the patients in the intraoperative period and in the first 2 days after their admission to intensive care unit, before and after albumin infusion. The blood samples were delivered to the Physiology Laboratory and hemorheological parameters (erythrocyte aggregation, erythrocyte deformability, whole blood viscosity, plasma viscosity) were studied. Hemodynamic data, blood gas variables and data obtained with PICCO were recorded. The results were analyzed by using the 'GraphPad prizm 5' statistics program. The patients included in our study were in CHILD A and B groups. The reasons for transplantation were cryptogenic (9 patients), alcohol-related (4 patients), and viral (4 patient) liver cirrhosis. The graft source was alive donors in 14 patients and cadaveric donors in 3 patients. Average preoperative albumin level of the patients was in the normal range. There was no statistically significant difference in erythrocyte deformability after HSA replacement. There were marked decreases in terms of erythrocyte aggregation, blood and plasma viscosities after HSA. No significant difference was found in systolic, diastolic, mean arterial pressures, pulse and SVB values after HSA. However, in patients with systolic blood pressure below 90 mmHg and mean arterial pressure below 70 mmHg before HSA, significant increases were observed in both parameters after HSA infusion. SVB values determined postoperatively and at first day of intensive care unit stay were significantly lower than preoperative value. There were no statistically significant differences in CI, SVR, ESWL and GEDI values after HSA. However, in patients with a CI value below 3 lt/min before HSA, there was an upward trend in CI values after HSA. No statistically significant difference was found in pH, pCO2, pO2, HCO3, BE, SatO2 levels in blood gas analysis after HSA. The blood gas hemoglobin and hematocrit data showed a tendency to decrease 15 minutes after HSA, and a statistically significant decrease was observed after 90 minutes. There was no significant difference in lactate levels obtained from blood samples withdrawn before and 15 minutes after HSA however, the increase became statistically significant, 90 minutes after HSA. There was a significant decrease in hemoglobin and hematocrit values, at postoperative analysis and first day of intensive care unit stay. Platelet values tended to decrease but no statistically significant difference was found between preoperative, postoperative and intensive care first day values. Preoperative, postoperative and intensive care first day values of serum albumin were similar. No statistically significant difference was found in the fibrinogen values before and after HSA. Postoperative and intensive care INR values increased significantly compared to its preoperative value. As a result, in our study, HSA replacement in patients undergoing liver transplantation did not make a significant difference on erythrocyte deformability, but it caused a significant decrease in erythrocyte aggregation, whole blood viscosity and plasma viscosity. This reduction in erythrocyte aggregation, whole blood and plasma viscosities improves the fluidity properties of the blood and may create a more favorable hemorrhological condition for graft perfusion. In addition, it was found that there were increases in systolic blood pressure, mean arterial pressure and CI values after HSA replacement in liver transplant patients who were hypotensive. According to this result, it was thought that HSA did not affect blood pressure in normotensive patients, but it may have effects on improving blood pressure in hypotensive patients. In the literature, there are no studies examining hemorheological changes and the effects of HSA on hemorheology in patients undergoing liver transplantation. According to our study results, it was thought that hemorheological regulatory agents that can be used during liver transplantation, especially HSA, may create potential for achieving hemodynamic targets and improving microcirculation.