Background:Vascular resistance and flow rate during hypothermic machine perfusion (HMP) of kidneys is correlated with graft function.We aimed to determine the effects of increasing HMP pressure versus maintaining the initial pressure on kidney transplantation outcomes.Methods:We retrospectively reviewed the data of 76 primary transplantation patients who received HMP-preserved kidneys from 48 donors after cardiac death between September 1,2013,and August 31,2015.HMP pressure was increased from 30 to 40 mmHg (1 mmHg =0.133 kPa) in kidneys with poor flow and/or vascular resistance (increased pressure [IP] group;36 patients);otherwise,the initial pressure was maintained (constant pressure group;40 patients).Finally,the clinical characteristics and transplantation outcomes in both groups were assessed.Results:Delayed graft function (DGF) incidence,1-year allograft,patient survival,kidney function recovery time,and serum creatinine level on day 30 were similar in both groups,with improved flow and resistance in the IP group.Among patients with DGF,kidney function recovery time and DGF duration were ameliorated in the IP group.Multivariate logistic regression analysis revealed that donor hypertension (odds ratio [OR]:1.43,95％ confidence interval [CI]:1.02-2.06,P =0.035),donor terminal serum creatinine (OR:1.27,95％ CI:1.06-1.62,P =0.023),warm ischemic time (OR:3.45,95％ CI:1.97-6.37,P =0.002),and terminal resistance (OR:3.12,95％ CI:1.76-5.09,P =0.012) were independent predictors of DGF.Cox proportional hazards analysis showed that terminal resistance (hazard ratio:2.06,95％ CI:1.32-5.16,P =0.032) significantly affected graft survival.Conclusion:Increased HMP pressure improves graft perfusion but does not affect DGF incidence or 1-year graft survival.