| Objective: Prolonged mechanical ventilation(PMV)occurs frequently after cardiac surgery,worsening postoperative clinical outcomes and increasing patient morbidity and mortality.Several recent studies suggested that preoperative elevated serum levels of uric acid(UA)may be associated with the occurrence of PMV after cardiac surgery.Therefore,this study aims to investigate the relationship between preoperative serum UA levels and postoperative PMV in patients undergoing mechanical heart valve replacement(MHVR)and its predicting value for PMV.Methods: The clinical data of patients undergoing MHVR surgery in the Second Ward,Department of Cardiovascular Surgery of The First Affiliated of Anhui Medical University from January 2017 to December 2017 were analyzed retrospectively.Preoperative and intraoperative variables in this study were consulted from previous reports and they included sex;age;weight;history of smoking and previous cardiac surgery;comorbidities including hypertension,diabetes,coronary artery disease,and chronic obstructive pulmonary disease;UA,serum creatinine(SCr),albumin(ALB),and hemoglobin(Hb);estimated glomerular filtration rate(e GFR);left ventricular ejection fraction(LVEF);pulmonary artery systolic pressure(PASP);type of surgery;other related procedures;length of aortic cross clamp(ACC)and cardiopulmonary bypass(CPB).All patients were divided into the PMV group(>48h)and the control group(?48h)according to whether the duration of postoperative mechanical ventilation was greater than 48 hours.Spearman correlation coefficient was conducted to explore the relationship between preoperative serum UA levels and the occurrence of postoperative PMV.Univariate analysis was utilized to evaluate the association between pre-/intraoperative variables and postoperative PMV,and then,all variables with a P-value less than 0.05 were entered into the multivariate logistic regression analysis to determine the independent risk factors of PMV.Serum UA was analyzed as continuous variable and dichotomous variable(>6.11mg/d L vs.?6.11mg/d L)in this study.The predictive value of serum UA for PMV was undertaken using the receiver operating characteristic(ROC)curve,and the results were quantitatively described by the area under the curve.All reported P-values were 2-sided,and P-values less than 0.05 were considered significant.Results: A total of 311 patients were enrolled,including 164 males with an average age of 55.6 ± 11.4 years and 147 females with an average age of 54.2 ± 9.8 years.Postoperative PMV occurred in 38 patients,with an incidence of 12.2%.The mean preoperative serum UA concentration was 6.11 ± 1.94 mg/d L in all patients,and the mean UA concentration in the PMV group and the control group was 7.48 ± 2.24mg/d L and 5.92 ± 1.82mg/d L,respectively.There is a significant statistical difference between both groups(P<0.001).Rank correlation analysis showed that UA was positively correlated with postoperative PMV(r = 0.205,P<0.001).Univariate analysis of all included pre-/intraoperative variables suggested that age(P = 0.016),SCr(P<0.001),UA(P<0.001),LVEF<45%(P<0.001),e GFR<60ml·min-1·1.73m-2(P<0.001),CPB time>120min(P = 0.001)and coronary artery bypass graft surgery(P = 0.01)was significantly associated with the occurrence of PMV.The above variables were entered into the multivariate logistic regression,and the results showed that the preoperative elevated UA levels(OR = 1.44,95% CI: 1.15-1.81,P = 0.002),LVEF<45%(OR =5.52,95% CI: 2.04-14.92,P = 0.001),and CPB time>120min(OR = 4.81,95% CI:1.79-11.91,P = 0.002)were independent risk factors for PMV.After transforming serum UA into a binary variable,the results showed that the high UA level group was still more prone to develop PMV than the low UA level group(20.5% vs.4.8%,P<0.001).We entered the UA as a categorical variable into the same logistic regression model as described above.The results showed that the elevated serum UA levels(OR =4.99,95% CI: 1.95-12.81,P = 0.001),LVEF<45%(OR = 6.68,95% CI: 2.43-18.32,P= 0.001),and CPB time>120min(OR = 4.38,95% CI: 1.63-11.81,P = 0.002)were still independently correlated with the occurrence of PMV.The area under the ROC curve of UA predicting PMV was 0.72,95% CI: 0.635-0.806.When the sum of sensitivity and specificity was maximum,6.40 mg/d L was the optimal cut-off value,and the sensitivity and specificity was 76.3% and 63% at this time,respectively.Conclusions:(1)Preoperative elevated UA levels is an independent risk factor for PMV in MHVR patients and has a good clinical predictive value.(2)Preoperative LVEF <45% and intraoperative CPB time >120min are also independent risk factors for PMV.Therefore,improving the heart function before surgery and reducing the time of CPB during operation are also an important measure to prevent PMV.(3)This study is a retrospective observational study;thus,the above conclusions are needed to be verified in the future larger scale randomized clinical controlled trials. |
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