Viscoelastic versus conventional coagulation tests to reduce blood product transfusion in patients undergoing liver transplantation: A systematic review and meta-analysis

Background: Recent literature suggests viscoelastic test (VET)-guided transfusion management could be associated with reduced blood product administration in patients undergoing liver transplantation. Objectives: To assess the effectiveness of coagulation management guided by VETs compared with conventional coagulation tests (CCTs) in reducing blood product transfusion in patients undergoing liver transplantation. Design: Systematic review and meta-analysis of randomised (RCTs) and nonrandomised clinical trials performed according to PRISMA guidelines. The protocol was previously published (PROSPERO: CRD42021230213). Data sources: The Cochrane Central Library, PubMed/MEDLINE, Embase and the Transfusion Evidence Library were searched up to 30 th January 2022. Eligibility criteria: Setting: operating room. Patients: liver transplantation recipients. Intervention: use of VETs versus CCTs. Main outcome measures: the primary outcome was the mean number of transfused units for each blood product including red blood cells (RBCs), fresh frozen plasma (FFP), platelets (PLTs) and cryoprecipitate. Secondary outcomes included mortality rate, intensive care unit (ICU) and hospital length of stay (LOS). Results: Seventeen studies ( n  = 5345 patients), 15 observational and two RCTs, were included in this review. There was a mean difference reduction in RBCs [mean difference: -1.40, 95% confidence interval (95% CI), -1.87 to -0.92; P  < 0.001, I2  = 61%) and FFP units (mean difference: -2.98, 95% CI, -4.61 to -1.35; P  =  < 0.001; I2  = 98%) transfused in the VETs group compared with the CCTs one. A greater amount of cryoprecipitate was administered in the VETs group (mean difference: 2.71, 95% CI, 0.84 to 4.58; P  = 0.005; I2  = 91%). There was no significant difference in the mean number of PLT units, mortality, hospital and ICU-LOS. Conclusion: Our meta-analysis demonstrated that VETs implementation was associated with reduced RBC and FFP consumption in liver transplantation patients without effects on mortality and hospital and ICU-LOS. The certainty of evidence ranged from moderate to very low. Further well conducted RCTs are needed to improve the certainty of evidence.