Sato-Boku et al. BMC Anesthesiology (2019) 19:168 https://doi.org/10.1186/s12871-019-0839-y RESEARCHARTICLE Open Access Comparison of disinfection effect between benzalkonium chloride and povidone iodine in nasotracheal intubation: a randomized trial Aiji Sato-Boku1* , Keiji Nagano2, Yoshiaki Hasegawa3, Yuji Kamimura4, Yoshiki Sento4, MinHye So4, Eisuke Kako4, Masahiro Okuda1, Naoko Tachi1, Hidekazu Ito5, Yushi Adachi6 and Kazuya Sobue4 Abstract Background: Nasotracheal intubation can potentially result in microbial contamination from the upper respiratory tract to the lower respiratory tracts. However, an ideal nasotracheal disinfection method is yet to be determined. Therefore, we compared the disinfection effects between benzalkonium chloride and povidone iodine in nasotracheal intubation. Methods: Overall, this study enrolled 53 patients aged 20–70 years who were classified into classes 1 and 2 as per American Society of Anesthesiologists-physical status and were scheduled to undergo general anesthesia with NTI. Patients who did not give consent (n = 2) and who has an allergy for BZK or PVI were excluded from the study. The patients were randomly divided into two groups on the basis of the disinfection method: BZK (n = 26, one patient was discontinued intervention) and PVI (n = 25). 50 patients were assessed finally. The subjects’ nasal cavities were swabbed both before (A) and after disinfection (B), and the internal surface of the endotracheal tube was swabbed after extubation (C). The swabs were cultured on Brain heart infusion agar and Mannitol salt agar. The number of bacteria per swab was determined and the rates of change in bacterial count (B/A, C/B) were calculated. The growth inhibitory activity of the disinfectants on Staphylococcus aureus were also investigated in vitro. Results: Although the initial disinfection effects (B/A) were inferior for benzalkonium chloride compared with those for povidone iodine, the effects were sustained for benzalkonium chloride (C/B). In the in vitro growth inhibitory assay against S. aureus, benzalkonium chloride showed higher inhibitory activity than povidone iodine. Conclusion: Although both disinfectants were inactivated or diffused/diluted over time, benzalkonium chloride maintained the threshold concentration and displayed antimicrobial effects longer than povidone iodine; therefore, benzalkonium chloride appeared to show a better sustained effect. Benzalkonium chloride can be used for creating a hygienic nasotracheal intubation environment with sustained sterilizing effects. Trial registration: UMIN-CTR (Registration No. UMIN000029645). Registered 21 Oct 2017. Keywords: Nasotracheal intubation, Benzalkonium chloride, Povidone iodine, Bacteremia * Correspondence: [email protected] 1Department of Anesthesiology, Aichi Gakuin University School of Dentistry, 2-11 Suemori-dori, Chikusa-ku, Nagoya 464-8651, Japan Full list of author information is available at the end of the article © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Sato-Boku et al. BMC Anesthesiology (2019) 19:168 Page 2 of 8 Background Subjects Nasotracheal intubation (hereafter referred to as “NTI”) Overall, this study enrolled 53 patients aged 20–70 years is frequently necessary during dental, maxillofacial, and who were classified into classes 1 and 2 as per American oropharyngeal surgeries. This method is also useful Society of Anesthesiologists-physical status (hereafter re- while operating on patients with respiratory insuffi- ferred to as “ASA-PS”) and were scheduled to undergo ciency, patients who require long-term maintenance of general anesthesia with NTI. Patients who did not give the airway in the intensive care unit and patients in consent (n = 2) and who has an allergy for BZK or PVI whom orotracheal intubation is difficult because of tris- were excluded from the study. The patients were mus. However, some complications associated with NTI randomly divided into two groups on the basis of the include epistaxis [1, 2], bacteremia [3], retropharyngeal disinfection method: BZK (n = 26, one patient was dis- perforation [4], and partial or complete obstruction of continued intervention) and PVI (n = 25). 50 patients the tube [5, 6]. NTI complications are some of the many were assessed finally (Fig. 1). causes of anesthesia-related mortality [7]. Although several effective preventive measures against Anesthesia, sample collection, and microbial count epistaxis and retropharyngeal perforation have been re- The same method of anesthesia was employed for all pa- ported [8–10], an effective disinfection method during tients. No premedication was administered. After a pa- NTI is yet to be determined. In fact, dental procedures tient walked independently to the operating theater, the under general anesthesia with NTI demonstrate a higher standard vital monitors (electrocardiogram, blood pres- incidence of bacteremia compared with those conducted sure and oxygen saturation) were monitored. Anesthesia under local anesthesia [3]; moreover, patients with pros- was induced using propofol (1–2 mg/kg), remifentanil thetic heart valves, immunodeficient patients, diabetic (0.2 μg/kg/min.), and fentanyl (100 μg), with rocuronium patients, and patients taking steroids are at an increased (0.6 mg/kg) used as a neuromuscular blocking agent. risk of bacteremia, and such patients require antibiotic Until the effects of the neuromuscular blocking agent prophylaxis [11]. Reports describing the presence of became apparent, mask ventilation was implemented for NTI-related bacteremia also exist [11, 12]. Bacteremia is all patients using 100% oxygen. While mask ventilation likely caused by transferring intranasal bacteria into the was being performed, the subjects’ inferior nasal passage respiratory tract. Therefore, the disinfection of the nasal was swabbed with a sterile cotton swab before disinfec- mucosa before nasal intubation is crucial for avoiding tion (A). The subjects’ nasal cavities and inferior nasal the contamination of respiratory organs by nasal passages were adequately disinfected twice each using a microorganisms. sterile cotton swab with BZK (ZALKONIN® SOLUTION In Japan, benzalkonium chloride (hereafter referred to 0.025, Kenei Phamaceutical Co., Ltd., Osaka) or PVI as “BZK”) and povidone iodine (hereafter referred to as (POVIDONE-IDOINE SOLUTION 10% ⌈MEIJI⌋ Nitto “PVI”) are generally used as NTI disinfectants. A com- Medic Co., Ltd., Toyama). BZK and PVI were applied at prehensive literature search was performed using normal clinical concentrations of 0.025 and 5%, respect- PubMed, the Cochrane Central Register of Controlled ively. Next, the patients’ inferior nasal passages were Trials and EMBASE. However, to the best of our know- swabbed again with sterile cotton swabs after disinfec- ledge, the authors were unable to identify any previous tion (B). Then, tramazoline nasal drops were adminis- reports comparing the outcomes of disinfection effects tered to the nasal cavity and NTI was conducted after between these two disinfectants. Therefore, we investi- the muscle relaxant was observed to take effect. In all gated the disinfection effects of BZK and PVI when used cases, we maintained general anesthesia using Total for disinfection in NTI. Intra Venous Anesthesia. After the surgery, the internal surface of the endotracheal tube (inner surface 1 cm Methods from the tip of the tube) was swabbed immediately after Ethics approval and consent to participate extubation (C). We focused on how much bacteria that This study was approved by the Ethics Committee at the invaded from the upper airway to the lower airway School of Dentistry, Aichi Gakuin University (Approval during intubation was suppressed by long-term disinfec- No. 495) and was registered prospectively in the UMIN- tion effect. If we swabbed the outer surface of the endo- CTR as a clinical trial on 21 Oct 2017. (Registration No. tracheal tube, we could not avoid contamination by UMIN000029645). Our study adhered to CONSORT nasal bacteria during extubation. Therefore, we swabbed guidelines. The first patient was recruited and registered the the internal surface of the endotracheal tube. on 23 Oct 2017 (https://upload.umin.ac.jp/cgi-bin/ctr/ctr_ After collecting the specimens, only the swab head view_reg.cgi?recptno=R000033873). We obtained written was cut off. The samples from (A) and (C) were placed informed consent from all patients after providing them in 10 ml of sterile physiological saline and the samples with adequate explanation regarding the research aims. from (B) were placed in 40 ml of sterile physiological Sato-Boku et al. BMC Anesthesiology (2019) 19:168 Page 3 of 8 Fig. 1 Consolidated Standards of Reporting Trials (CONSORT) recommended description of patient recruitment saline to dilute the disinfectants (BZK or PVI) that were The evaluation of parameters absorbed by the swab. The samples were refrigerated The preoperative patient attributes of sex, age, and submitted for examination