Postoperative Central Venous Pressure Is Associated With Acute Kidney Injury And Mortality In Patients Undergoing Coronary Artery Bypass Grafting

BackgroundAcute kidney injury is a serious postoperative complication in patients undergoing coronary artery bypass grafting(CABG).Central venous pressure(CVP)is commonly used as a measure of venous congestion,which has been suggested to make great contribution to the development of postoperative acute kidney injury in recent studies.We aimed to investigate the association of postoperative CVP with acute kidney injury and mortality in patients undergoing CABG.MethodPatients who underwent CABG between 2001 and 2012 in the Medical Information Mart for Intensive Care Ⅲ database were included and divided into two groups according to the optimal cutoff value of CVP for postoperative acute kidney injury determined by the receiver operating characteristic(ROC)curves.Survival curves were estimated using the Kaplan-Meier method.Multivariate regression models were used to determine the association of CVP with acute kidney injury and mortality.A 1:1 propensity score matching method was performed to balance the influence of potential confounding factors.ResultsA total of 4480 patients were included.The ROC analysis indicated that the optimal cutoff value of CVP for postoperative acute kidney injury was 10.9,thereby patients were divided into high CVP group(CVP≥10.9 mmHg)and low CVP group(CVP<10.9 mmHg).There was significant difference between the two groups regarding the baseline characteristics.Patients in high CVP group presented with higher length of stay in intensive care unit(1.91(1.16,3.01)vs 2.82(1.36,4.88),p<0.001),incidence of acute kidney injury(430(17.7%)vs 623(30.5%),p<0.001),in-hospital mortality(8(0.3%)vs 50(2.4%),p<0.001)and 4-year mortality(202(12.1%)vs 236(18.7%),p<0.001).After propensity score matching,1529 pairs of score-matched patients were generated,and the baseline characteristics between the two groups were basically consistent.The multivariate logistic model showed that patients with CVP≥10.9 mmHg had a significantly higher risk of postoperative acute kidney injury than those in low CVP group in the entire cohort(OR:1.861(1.588,2.182),p<0.001)and the propensity score matching subset(OR:3.516(1.341,9.221),p=0.011).The multivariate regression model also indicated that patients with higher CVP had higher risk of in-hospital mortality in both entire cohort(OR:4.252(1.961,9.222),p<0.001)and the propensity score matching subset(OR:3.516(1.341,9.221),p=0.011),as well as the 4-year mortality in both entire cohort(HR:1.437(1.175,1.756),p<0.001)and the propensity score matching subset(HR:1.356(1.065,1.726),p=0.013).The survival curves showed that patients with CVP≥10.9 mmHg had a significant lower 4-year survival rate in the entire cohort(p<0.001)and the propensity score matching subset(p=0.009).ConclusionA mean CVP above 10.9 mmHg within the first 24 hours after cardiac surgery was independently associated with a higher risk of postoperative acute kidney injury and mortality in CABG patients.