Risk Factors Associated With Positive Bacterial Culture In Salvaged Red Blood Cells During Cardiac Surgery And Postoperative Infection Incidence

Background and Objective:The utilization of large volumes of blood products is more likely to occur when patients undergo open heart surgery owing to the inherent complexity of cardiopulmonary bypass(CPB)and associated surgical procedures.Indeed,the 15-20% of patients undergoing cardiac procedures are estimated to consume over 80% of all blood products in operative settings.Active patient blood management(PBM)can not only reduce blood transfusion,relieve the pressure placed on blood resources,but also reduce complications caused by blood transfusion,reduce postoperative morbidity and mortality,and prolong survival time.PBM is a multimodal,multidisciplinary approach that centers around three main goals: 1)preoperative early monitoring and treatment of anemia;2)minimizing intraoperative blood loss;3)optimizing the patient-specific tolerance of anemia with a view to minimizing blood product transfusions and improve patient outcomes.Intraoperative cell salvage(ICS)and the infusion of salvaged red blood cells(s RBCs)form key components of PBM strategies in cardiac surgery patients.Relative to allogeneic blood,s RBCs exhibit notable advantages including good oxygen-carrying capacity and a high anti-acid buffering rate,and it is more convenient and efficient than allogeneic blood when treating patients with rare blood types or individuals suffering from emergency hemorrhage.In the reality of severe shortage of blood resources,ICS has become an indispensable and important technology for saving lives.However,the use of ICS is not without risks,one of which is microbial contamination.At present,there are few literature reports on the positive rate of bacterial culture in s RBCs,and all of them are studies with small sample sizes,and the impact of reinfusion of contaminated s RBCs on patients’ postoperative infectious complications is also controversial.There are two main purposes of this study: 1)analysis of the incidence,bacterial species and possible risk factors of s RBCs bacterial contamination;2)The correlation between infusion of s RBCs and postoperative infection complications in patients,so as to provide clinical evidence for the improvement of operating room management and perioperative surgical nursing measures.Methods:This study is a single-center,prospective study,and finally included 210 consecutive patients who underwent ICS in cardiac surgery between July 2021 and July 2022 in the Department of Cardiovascular Surgery of The First Affiliated Hospital of Air Force Military Medical University.Hospitalization,operation,short-term prognosis and perioperative indicators were collected.Part 1: Analysis of the incidence,bacterial species and risk factors of s RBCs bacterial contaminationThis part adopts the single-center prospective case-control study method,prospectively collects and records patients’ baseline data,surgical data,etc.Bacterial culture was carried out on the s RBCs obtained during the operation,and the incidence and type of bacterial contamination of s RBCs were clarified.In some patients,the air particle content in the operating room was dynamically measured at the same time T Then,according to the blood culture results of s RBCs,they were divided into culture(+)group and culture(-)group and statistical methods such as one-way analysis of variance,chi-square test or Fisher’s exact test were used to compare the baseline data and intraoperative indicators between the two groups.Based on univariate analysis combined with clinically significant factors,a multivariate Logistic regression model was established to obtain independent risk factors for bacterial contamination of s RBCs after correcting clinical variables.Part 2: Analysis of postoperative infection in patients with infusion of s RBCsThis part adopts the method of prospective cohort study.The above-mentioned two groups of patients collected venous blood on the first day and the third day after operation for bacterial culture to clarify the types of bacteria in patients with bacteremia.At the same time,the type of postoperative infection was judged based on the CDC/NHSN standard,and whether there was a significant difference in the incidence of postoperative infection between the two groups was compared.The patients were further divided into the infection group and the non-infection group according to whether the patients had postoperative infection: the perioperative indicators between the two groups were statistically analyzed by univariate analysis.Based on univariate analysis combined with common infection risk factors,a multivariate Logistic regression model was established,clinical variables were corrected,and the correlation between positive bacterial culture of s RBCs and postoperative infection was obtained Results:Part 1: Analysis of the incidence,bacterial species and risk factors of s RBCs bacterial contamination1.100(49%)s RBCs had positive bacterial cultures,among which S.epidermidis was the most common,accounting for 64%(n=64),and S.haemolyticus(6%),S.caprae(3%),S.hominis(8%),S.cohnii(2%),S.capitis(5%),S.saccharolyticus(4%),M.luteus(3%),Str.viridans(2%),C.diphtheriae(1%),B.fragilis(1%),A.ursingii(1%).The positive rate of blood culture in the culture(+)group was significantly higher than culture(-)group on the third day after operation.However,the types of blood culture bacteria in each patient on the 1st and 3rd day after operation were not consistent with the types of bacteria in s RBCs.2.In the 100-class purification operating room of cardiovascular surgery,the dust particle count in the operating room was detected every 2 hours in the first 40 patients,including 18 cases in the s RBCs culture(+)group and 22 cases in the culture(-)group.There was a statistically significant difference in the counts of dust particles with a0.5 μm between the two groups.3.After establishing the univariate analysis and multivariate Logistic regression model related to the positive bacterial culture of s RBCs,it was found that BMI ≥ 25(OR2.08,95 % CI 1.08-4.00,P=0.03),smoking history(OR 1.99,95 % CI 1.03-3.86,P=0.04),operation time ≥ 277.5 min(OR 5.58,95 % CI 2.86-10.86,P<0.01),high number of people in the operating room(OR 1.19,95 % CI 1.05-1.36,P=0.01)and higher surgical case order(OR 2.07,95 % CI 1.03-4.17,P=0.04)were independent risk factors.Part 2: Analysis of postoperative infection in patients after reinfusion of positive s RBCs1.The positive rate of blood culture in the s RBCs culture(+)group was significantly higher than that in the s RBCs culture(-)group on the third day after operation(P=0.04).However,the types of bacteria in the blood culture of each patient on the1st and 3rd day after operation were not consistent with the types of bacteria in s RBCs2.Overall,32 patients(15.7%)had postoperative infection,including 8 cases of pneumonia,16 cases of bloodstream infection,5 cases of surgical site infection,and3 cases of urinary tract infection.Univariate analysis establishing associations with postoperative infection found age≥54.5(P = 0.01),BMI ≥ 25(P = 0.08),pulmonary disease(P = 0.06),combined valve and CABG surgery(P = 0.09),higher transfusion of allogeneic RBCs during operation(P = 0.08),positive bacterial culture of s RBCs(P = 0.02)were significantly associated with postoperative infection.Among the above factors,the results of the multivariate Logistic regression model showed that only positive bacterial culture of s RBCs(OR 2.62,95% CI 1.16-5.90,P=0.02)and age≥54.5(OR 1.04,95% CI 1.00-1.08,P=0.04)were independent risk factors for postoperative infection.Conclusions:1.The incidence of positive bacterial culture of s RBCs was 49%,and the most common bacteria was S.epidermidis.2.The patient with obesity,smoking history;the long operation time during the operation,the higher surgical case order,and the number of people in the operating room were risk factors for positive bacterial culture of s RBCs.3.Positive bacterial culture of s RBCs、age≥54.5 are independent risk factors for postoperative infection.