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 (1). Patient blood management (PBM) is a multimodal, multidisciplinary approach that centers around three main goals: improving preoperative red blood cell (RBC) counts as through the early detection and treatment of anemia, minimizing intraoperative blood loss through strategies such as intraoperative cell salvage (ICS), and optimizing the patient-specific tolerance of anemia (2). PBM can alleviate the pressure placed on blood resources while also reducing rates of transfusion-related complications and contributing to improved postoperative patient outcomes (3). ICS and the infusion of sRBCs form key components of PBM strategies in cardiac surgery patients. Relative to allogeneic blood, sRBCs 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 (4).

Intraoperative cell salvage has become an essential life-saving technology when performing complex operations. However, the benefits of a given clinical strategy must be carefully weighed against the potential adverse outcomes of such treatment. Manuel detected Gram-positive bacteria, primarily Staphylococcus epidermidis, in sRBCs samples collected from shed blood following washing with Cell Saver (CS) machines in patients undergoing cardiac surgery (5). They further observed higher rates of postoperative infections in patients that underwent cardiac surgery with ICS as compared to cardiac surgery patients for whom salvage was not performed (6). Even so, a meta-analysis of over 4,000 patients found ICS to be associated with a 28.7% reduction in the overall risk of infective morbidity (7). As such, whether the transfusion of sRBCs with positive bacterial culture results is likely to impact patients remains a matter of some controversy (8). Prior studies of ICS use in patients undergoing cardiac surgery have largely failed to conduct an adequate evaluation of the associated costs and benefits of such treatment. Accordingly, this study was developed to assess rates of sRBCs culture positivity in cardiac surgery patients, risk factors associated with such positivity, and the relationship between sRBCs culture positivity and postoperative infectious morbidity in these patients.

This study was developed to explore the incidence of positive bacterial culture in sRBCs in the context of cardiac surgery, to identify predictors of positivity, and to evaluate its impact on postoperative infection incidence in these patients in an effort to guide the better prevention of microbial.

In the 2017 EACS/EACTA guidelines, CS has a category IIa recommendation for routine use as a component of PBM strategies during cardiac surgery in adult patients with the goal of minimizing the need for allogeneic blood products (12). While advantageous, however, this savage strategy has been shown to reduce coagulation factors and contribute to higher rates of postoperative infective morbidity (13, 14). This is particularly important given that infections are the most common non-cardiac complication following cardiac surgical procedures and they have a pronounced impact on patient survival and readmission rates (15). Accordingly, this study was designed to explore the relationship between CS and infection.

The washing process employed by CS devices has been shown to remove the majority of bacteria from sRBCs preparations (16–18), but 10–30% of the bacteria may remain after washing (8). Here, positive bacterial cultures were obtained for 49% of cardiac surgery patient sRBCs samples, with S. epidermidis being the most prevalent microbe in these samples. S. epidermidis is generally a harmless commensal bacterium that is commonly detected on the human skin and mucosal surfaces, and that can also readily adhere to medical devices such that it represents a clinically important opportunistic pathogen. As it can readily form a biofilm, S. epidermidis can resist antibiotic treatment, contributing to persistent or prolonged infections. The majority of bacteria isolated from bloodstream infection patients are Gram-positive bacteria, including coagulase (−) bacteria such as S. epidermidis (19), which is a common causative agent in cases of nosocomial blood infections (20). S. epidermidis was previously reported to be associated with 69% of culture (+) in sRBCs following the CS-mediated washing of salvaged blood for patients undergoing cardiac surgery. But it did not demonstrate the effect on patients after surgery (5). In contrast, the present results offer insight into postoperative infection incidence in patients that were transfused with bacterially positive sRBCs.

It remains controversial as to whether the use of CS devices resulting in positive sRBCs culture contributes to higher infective morbidity. One report demonstrated that RBCs transfusion was associated with infections and that relative to a liberal transfusion strategy, a more restrictive strategy was associated with a lower risk of infection (21). In a study of cardiac surgery patients, ICS was directly associated with increased infective morbidity, although the surgery types in that study were restricted to CABG and valvular surgery (6). A separate report observed no adverse patient outcomes despite the frequent contamination of sRBCs with Gram-positive skin-derived bacteria commensal species and low levels of endotoxin, although that study is relatively old and had a small sample size (22). In the present study, significant differences in the length of ICU stay, duration of ventilation, and postoperative bloodstream infection rates were observed between patients with and without detectable positive bacterial culture in sRBCs. However, our study found that the bacteria cultured in sRBCs were not completely consistent with the bacteria cultured in postoperative infected patients, which seems to weaken the link between sRBCs culture positive and postoperative infection. However, forward univariable and multivariable logistic regression analyses for independent factors associated with postoperative infection also indicated that culture (+) in sRBCs is the independent risk factor for contributing to postoperative infection in this study. These findings thus suggest that positive sRBCs bacteria culture results are indicative of at least some level of safety risk.

Previous reports have explored risk factors associated with culture (+) in sRBCs, yielding varying outcomes that may be attributable to differences in patients, exposure time, intraoperative procedures, and the surgical environment (including operating room cleanliness). One study of cardiac surgery patients found that those with a BMI ≥25 who underwent valvular surgery tended to be more susceptible to S. epidermidis cultures (+) in sRBCs (5). Another controlled study compared new and old operating rooms and detected fivefold lower bacterial counts in sRBCs samples prepared in the new operating room relative to the old room, indicating that operating room cleanliness is likely to impact bacterial deposition (23). Both longer operative duration and higher case order have previously been established as significant infection-related risk factors (24, 25). Those patients with a BMI ≥25 and a preoperative history of smoking were more likely to exhibit culture (+) in sRBCs. In these patients, preadmission education can be tailored toward the promotion of dietary control, smoking cessation, and appropriate cleaning procedures, while postoperative efforts should focus on monitoring for a range of infection-related indicators so that vigorous treatment can be rapidly deployed when appropriate. The present results also support the status of longer operative duration, higher surgical case order, and more staff in the operating room as independent predictors of positive bacterial culture in sRBCs. Contaminant accumulation during an initial case has been shown to be perpetuated and amplified for subsequent cases, as in one example in which 0 and 7% of the operating room was found to be contaminated prior to the treatment of patient 1 and patient 2, respectively (26). This is consistent with the present results demonstrating that higher case order and higher levels of contamination may contribute to bacterial transmission. Higher volumes of operating room traffic due to staffing changes can further increase this risk, and the reduction of unnecessary traffic by assigning staff to particular cases rather than shifts could potentially mitigate such contamination and associated microbial transmission (24). Most importantly, it is vital that standardized operating room nursing procedures be developed and that operating room management be conducted carefully. This includes outpatient and pre-admission education, the strict and timely administration of antibiotics, the monitoring of operating room air quality, the sterilization of surgical instruments, the minimization of the operative duration, and the elimination of operating room traffic wherever possible. Implementing comprehensive nursing interventions for risk factors can effectively enhance patient prognostic outcomes and quality of life.

This study is subject to some limitations, including the fact that the study population was relatively small. Recent reports have suggested that adding vancomycin can eliminate the bacterial of sRBCs when using CS devices (27), but this approach remains to be tested in the context of cardiac surgery. In future studies, we will focus on actively collaborating with other centers to increase the study sample size and to conduct bacterial sensitivity testing aimed at identifying the lowest concentrations of the most effective antibiotics capable of lowering rates of culture positivity.

The present results confirmed that positive bacterial culture in sRBCs is evident in cardiac surgery patients, and that was associated with patient BMI, history of smoking, operative duration, operating room traffic, and surgical case order. The use of these positive sRBCs was, in turn, associated with postoperative infections and other adverse outcomes.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

This trial was reviewed and approved by the Ethics Committee of Xijing Hospital, which has been registered in the Chinese Clinical Trial Registry (ChiCTR2200060439). All the patients signed an informed consent form. The patients/participants provided their written informed consent to participate in this study.

JL, BZ, and ZJ designed the clinical study. YZ, XY, and TC collected the clinical data. YZ, CY, and TC analyzed the data and drafted this manuscript. YZ, BZ, and ZJ modified the manuscript. All authors revised and approved the final manuscript.