This study investigated the effectiveness of NST in preventing the occurrence of CLABSI before and during the COVID-19 pandemic.

Implementation of the NST has been associated with improved survival outcomes in critically ill patients with COVID-19 [13]. However, there have been no reports focusing on CLABSI and no studies on the NST in Japan. In Japan, the NST provides multi-disciplinary nutritional management to patients with malnutrition or those at risk of malnutrition to promote the healing of underlying diseases and to prevent complications such as infections. The training of healthcare professionals on infection prevention manuals for central venous catheter management is effective in reducing device-standardized infection rates and preventing CLABSI [14]. In the NST group, the documentation of the standards of the CLABSI prevention manual and the establishment of a system for implementing aseptic preparation could have contributed to the suppression of CLABSI occurrence. In our study, 93.6% and 59.5% of facilities used closed infusion systems and in-line filters, respectively, with no significant between-group difference. The use of antiseptics on central venous catheter insertion sites has demonstrated clinical preventive effects; among them, chlorhexidine–alcohol significantly reduces the incidence of CLABSI compared with povidone–iodine [15]. In addition, current guidelines recommend alcohol with chlorhexidine added at a concentration of > 0.5% [16]. Among the target facilities, povidone–iodine was the most widely used antiseptic. Chlorhexidine-induced anaphylaxis has been reported to be more common in the Japanese population than in the Caucasian population [17]. Accordingly, 10% povidone–iodine should be considered an option for skin disinfection; however, education on its usage is important. Fat emulsion administration is a risk factor for CLABSI [18]. Specifically, following fat emulsion administration, microorganisms that have entered the intravenous infusion line may proliferate over time. Therefore, it is important to flush the line with a sufficient saline volume to prevent CLABSI development. In both groups, the saline flush volume after fat emulsion administration was ≤ 10 mL in more than half of the patients. The required saline flush volume may be approximately twice the capacities of the indwelling needle, catheter, and connected device. Taken together, the administration of fat emulsions that promote microbial growth is an independent risk factor for CRBSI; therefore, it should be followed by an appropriate saline flush volume and frequent infusion set changes [19, 20].

During the COVID-19 pandemic, there was postponement or cancellation of elective surgeries as well as a need for an increased number of intensive care unit beds. Additionally, patients with COVID-19 have shown an increased incidence of various healthcare-associated infections, comorbidities, and long-term hospitalization [21, 22]. In our study, the incidence of CLABSI after the pandemic was non-significantly higher than that before the pandemic, which is consistent with previous findings [21, 22]. In 2020, the CLABSI incidence rate increased and decreased in the NST and non-NST groups, respectively. Before the pandemic, teamwork contributed to reducing the infection rate. During the pandemic, many facilities in the NST group were classified as Infection Control and Prevention Level 1; additionally, they received an increased number of patients since they accepted critically ill patients, which required targeted measures. Accordingly, during the pandemic, team activities were impeded and became stagnant. According to the Ministry of Health, Labour and Welfare's report on "Number of medical institutions accepting COVID-19 patients by national, public, and private institutions and the percentage of acceptances" as of November 2020, the acceptance rates of COVID-19 patients at national and public medical institutions are high at 58% and 75%, respectively, while the rate at private medical institutions is low at 17% [23]. This study was not able to collect data on the acceptance of COVID-19 patients at participating facilities. However, as shown in Table 1, we speculated that the restriction on the admission of COVID-19 patients may have been one of the factors that reduced the incidence of CLABSI since the non-NST group had a higher proportion of private medical institutions than the NST group.

This study has several limitations. First, it was a retrospective observational study, and we could not adjust for all confounding factors affecting the incidence of CLABSI.

Second, although there are numerous NST facilities operating nationwide, we included a small number of facilities which limits generalizability. Third, the incidence of CLABSI may be affected by various factors, including the infection control system, and further study is needed to prove the effect is limited to NST. Multi-center studies accounting for these limitations are warranted to focus on the coordination system of medical teams such as the NST and infection control teams. Elucidating the effectiveness of the NST in preventing the occurrence of CLABSI could inform the improvement of the NST activity with respect to the fight against emerging and unknown infections.

In our study, the incidence of CLABSI during the COVID-19 pandemic was lower in the NST group than in the non-NST group, which indicates the effectiveness of the NST in preventing the occurrence of CLABSI.