Association of Platelet Count and Platelet Transfusion With Serotonin Level During Living Donor Liver Transplantation: Possible Connection to Graft Regeneration.

ABSTRACT

BACKGROUND: We recently showed that platelet counts and the amount of platelet transfusion during liver transplantation are positively associated with early graft regeneration. It was hypothesized that platelet-derived serotonin mediates liver regeneration. OBJECTIVES: This study aimed to evaluate the association between intraoperative platelet count, platelet transfusion, and serum serotonin level. METHODS: Thirty-two recipients undergoing living-donor liver transplantation were enrolled into this prospective observational study. Serum platelet counts and serotonin levels were measured at the following times anesthetic induction, start of the anhepatic phase, before graft reperfusion, 5 minutes/1 hour/3 hours/5 hours after graft reperfusion, and before/after platelet transfusion. Serotonin was measured by using a liquid chromatography tandem mass spectrometry. RESULTS: Serotonin level at the anesthetic induction was 24.5 µg/mL (interquartile range, 14.6 to 38.1 µg/mL). During surgery, serial changes in platelet counts and serotonin levels showed a similar trend they decreased during the anhepatic phase, increased during the first hour after graft reperfusion, and thereafter gradually decreased. Serotonin level was positively correlated with platelet counts (correlation coefficient = 0.620, P < .001). Allogeneic platelet transfusion significantly increased platelet count from 22 (19-31) × 109/L to 53 (50-81) × 109/L (P = .008) and it also increased serum serotonin from 11.04 (6.41-15.34) µg/mL to 34.26 (25.86-41.94) µg/mL (P = .008). CONCLUSIONS: Our findings indicate that allogeneic platelets could act as effector cells deriving serotonins. Also, our findings support the hypothesis that the association between platelets and post-transplantation graft regeneration is mediated by serotonin. Further studies are warranted regarding the respective role of serotonin and other platelet-derived molecules mediating liver regeneration.