Many useful aspects of oral care in the perioperative period have been reported, including a decrease of complications of infections and postoperative pneumonia, and shortened hospitalization [1–3, 16–18]. We performed a randomized controlled feasibility study of CPC and PVP-I products in Japan for better selection of the oral care product in the perioperative period. Chlorhexidine hydrochloride (CHX) is commonly used as antiseptic mouthwash in oral care management. However, in Japan, the use of CHX is restricted due to allergy concerns. Instead, PVP-I and CPC are commonly used as alternatives to CHX in oral care management. In the first report of this study, we compared changes in the bacteria counts and bacterial flora between PVP-I and CPC in POM [14]. CPC was found to maintain an antibiotic-mediated decrease of Streptococcus, which is related to postoperative pneumonia, from the day after surgery until 1 week after surgery. This result suggests that CPC might support the antibacterial effects of antibiotics in the perioperative period.
The current study was conducted from a clinical perspective. Postoperative inflammatory reactions are caused by surgery itself, as well as complications, including surgical site infection (SSI), pneumonia, urinary tract infection, and other bacterial infections. Thus, we examined how PVP-I and CPC used in the perioperative period might be related to the severity of postoperative inflammation. CRP is a protein that appears in blood several hours after cellular destruction in tissues caused by infection or inflammatory disease. As an inflammation marker, CRP is extremely useful for understanding of disease status and detection of postoperative infection [19–21]. In this study, evaluation was performed based on a CRP threshold of 5 mg/dL. This or similar values have been used in many other studies [22–27] as an index of bacterial infection. The CPC group had significantly fewer subjects with high CRP (≥ 5 mg/dL) compared to the PVP-I group. CRP increases after surgery, and the PVP-I group had more subjects with severe inflammation compared to the CPC group, based on division of each group into those with CRP ≥ 5 and < 5 mg/dL. These data are related to the usefulness of CPC, as suggested in our previous report [14]. POM may also affect the CRP level [28], but POM was provided to both groups in the current study, with no group without oral care. Thus, it is unlikely that POM influenced the comparison of CRP, which supports the conclusion that CPC used in support of oral care had a beneficial effect on CRP.
The relationship of CRP with Shannon Index and OTU counts in tongue coating before surgery (upon intubation) was also analyzed. Postoperative pneumonia is a common postoperative complication associated with changes of bacteria in the oral cavity. In most cases of patients that develop postoperative pneumonia, they are thought to be caused by bacteria in the oropharyngeal region that invade the respiratory tract during perioperative period. Therefore, in this study, we focused on bacteria at the dorsal surface of the tongue, which is act as a large reservoir of oropharyngeal bacteria. The Shannon Index increases as both the richness and the evenness of the bacterial community increase. The OTU counts indicates the bacterial richness; in other words, an ecosystem with many different species. Past reports suggest that oral care was insufficient when these indexes are high [29, 30]. The Shannon Index and OTU counts in tongue coating measured before surgery (upon intubation) were not affected by antibiotics, and showed that the oral environment is affected by preoperative professional oral care and self-care with use of individual products. The bacteria counts in tongue coating before surgery showed no significant difference in subjects with high and low CRP in the CPC and PVP-I groups, but the OTU counts and Shannon Index were significantly higher in subjects with high CRP in the CPC group. These findings suggest that oral cleanliness before surgery might be related to prevention of postoperative inflammation.
Surgical invasion level and age are also possible determinants of postoperative CRP. In multivariate analysis with postoperative development of inflammation (CRP ≥ 5 or < 5 mg/dL) as the objective variable, and age, operation time, product (PVP-I or CPC), and Shannon Index as dependent variables, the odds ratio for CPC use was 0.34 and that for the Shannon Index in tongue coating before surgery was 3.18. Since preoperative use of pasteurized products might affect the Shannon Index, there was a need to examine the correlation between the product and the Shannon Index. Pearson correlation coefficient analysis suggested no correlation between these variables, indicating that the product and Shannon Index immediately before surgery were independent factors.
In this study, high CRP may reflect an extensive postoperative reaction or the effects of complications. Clinically, there are also cases in which high CRP cannot be determined to be caused by a normal reaction or a complication. Since CRP is a contributor to diagnosis, it cannot be concluded that lower CRP denied development of complications based on the results of this study, but this is possible. In addition, few reports have suggested the efficacy of CPC in POM and the number of subjects in this study was small. Therefore, further work is required to examine the role of CPC in POM based on the findings in this study.