Academic Center

Orthophthalaldehyde (OPA) has been widely used in recent years as a second-generation endoscopic disinfectant due to its low irritant odour and short disinfection time, and the current use rate of OPA is 45% in Japan and 41% in the United States [1]. However, o-phthalaldehyde has been banned for cystoscopy disinfection because of its allergenicity, and the residual OPA can damage the gastrointestinal mucosa of patients [2], leading to isopropyl alcohol shock reaction [3]. Although existing national and international guidelines on endoscopy emphasise the role of cleaning steps in the removal of disinfectant residues [4], there are no studies on the amount of OPA residues in actual endoscopes and the methods of effective removal. Therefore, the present study was conducted to verify the residual amount of OPA after different cleaning times and methods, with the aim of providing a theoretical basis for the development and application of clinical standards.

Materials and Methods 

1.1 Test materials: High performance liquid chromatograph (HPLC), 1200 HPLC (Agilent technolo?gies Co., Ltd.); Vortex oscillator: SL-A256 (Scientific Indus?tries Co., Ltd.); 2,4-Dinitrophenylhydrazine: 99% (Guangzhou, China). Chemistry - 2611 - Chinese Journal of Disinfection 2016; 33( 12) Reagent Factory); Acetonitrile: chromatographic purity (MERK Company); o-phthalaldehyde: 99% (SIGMA - ALDRICH Company). The endoscopes used in this study were GIF-Q260J (Olympus), 0.55% CIDEX OPA disinfectant (Johnson & Johnson), 1 set of integrated endoscopic cleaning and disinfecting sink (Shenzhen Coriolis), and 1 set of automatic spray endoscopic cleaning and disinfecting tank (national utility model patent: ZL 2013 2 0185558.2). 2 0185558.2), 1 set of automatic endoscope cleaning and disinfection machine (Johnson & Johnson). 

1.2 Test method 

1.2.1 Grouping method The test was divided into four groups: Group 1 was a blank control group, which was sampled directly after cleaning with filtered water; Group 2 was a single-stream group, which was cleaned with a traditional tap; Group 3 was a spray cleaning group, which was supported by a flow pump, and a rotating spray head was installed on each wall of the cleaning tank, so that the cleaning water could be centrally emitted from the spray head and uniformly cover the rinsing of all the external surfaces of endoscopes; Group 4 was an automatic cleaning and disinfecting unit, which used an automatic cleaning and disinfecting machine, which was designed to clean and disinfect the endoscopes with the help of an automatic cleaning and disinfecting machine (Johnson & Johnson). Group 4 is an automatic cleaning and disinfecting group, which is cleaned by an automatic cleaning and disinfecting machine. Except for the blank control group where the endoscopes were not immersed in OPA, the endoscopes in the experimental group were immersed in OPA for 5 min. There were 12 endoscopes in each group, and the cleaning time was divided into 4 levels of 1, 2, 3 and 4 min. The cleaning time was divided into 4 levels of 1, 2, 3 and 4 min. The pressure of the water inlet pipe was controlled, and the cleaning water volume of each method was 10 L/min. 

1.2.2 Sampling method The cleaned endoscopes were blown dry with a high-pressure air gun, and the purified water was soaked in the outer surface of the insert for 5 min and then collected; the residual OPA concentration was analysed by a high-performance liquid chromatograph. The concentration of residual OPA was analysed by high performance liquid chromatography (HPLC). 

1.2.3 High performance liquid chromatography (HPLC) Chromatographic analysis was performed on a C18 column (optional Lunna-C18 column, 150 mm × 4.6 mm, 5 (m), mobile phase: acetonitrile: water = 50:50 (v/v), column temperature: 25 ℃, flow rate: 1 ml / min, detection wavelength: 220 nm, injection volume: 20 μl. 

1.3 Statistical Methods 

Statistical method 

The data were expressed as x now± s. SPSS 13.0 statistical software was used to analyze the data, and multifactorial analysis of variance (ANOVA) was used to statistically analyze the treatment method and treatment time, and LSD method was used to compare the OPA residues at different levels among the same group, and the difference of P＜0.05 indicated that the difference was statistically significant. 2 results of the application of analytic factor design data ANOVA analysis of the differences between different cleaning methods and treatment time of OPA residue, there are statistical differences, the need to use LSD for multiple comparisons. 2.1 LSD multiple comparisons of OPA residue of different cleaning methods Automatic cleaning and disinfection unit OPA residue is the lowest, and there is no statistically significant difference with the blank control group, the best removal effect. The single stream group had the highest OPA residues, with significant differences between all groups. Although there was no statistically significant difference in glutaraldehyde residue between the spray cleaning group and the automatic cleaning and disinfection unit, the mean values were higher in the spray cleaning group than in the automatic cleaning and disinfection unit and the blank control group (Table 1). Table 1 Comparison of the effects of different cleaning methods on OPA residues on the external surface of endoscopes Treatment (I) Treatment (J) MD (I - J) SE P 95% confidence interval Lower limit Upper limit Blank control Single stream -0.597* 0.085 0.000 -0.770 -0.423 Spray -0.265* 0.085 0.004 -0.438 -0.438 -0.438 -0.423 Spray -0.265* 0.085 0.004 -0.438 -0.438 -0.438 0.438 -0.092 Automatic decontaminating machine -0.127 0.085 0.144 -0.301 0.046 

Single stream Blank control 0.597* 0.085 0.000 0.423 0.770 Spray 0.332* 0.085 0.000 0.159 0.505 Automatic decontaminator 0.469* 0.085 0.000 0.296 0.643 Spray 0.262* 0.085 0.004 -0.438 -0.092 Automatic decontaminator 0.127 0.085 0.144 -0.301 0.046 

Shower Blank control 0.265* 0.085 0.004 0.092 0.438 

Single stream -0. 332* 0. 085 0. 000 -0. 505 -0. 159 

Automatic decontaminator 0.137 0.085 0.116 -0.036 0.311 

Automatic decontaminator Blank control 0.127 0.085 0.144 -0.046 0.301 

Single stream -0.469* 0.085 0.000 -0.643 -0.296 

Spray -0.137 0.085 0.116 -0.311 0.036 

Note: Based on observed means. *: Difference in means is significant at the 0.05 level. 

2.2 

LSD Multiple Comparison of OPA Residues at Different Cleaning Times The residue of OPA at 1 min cleaning time was significantly different from the other time points, and there was no significant difference between the 2 min and 3 min and 4 min time groups. There was no significant difference between the 2-min and 3-min and 4-min time groups. There was no change in the residue removal effect of OPA after 2 min of treatment (Table 2). Table 2 Comparison of the effects of different cleaning time on OPA residue on the external surface of endoscopes Treatment time (min) (I) Treatment time (min) (J) MD (I - J) SE P 95% confidence interval Lower limit Upper limit 1 2 0.300* 0.085 0.001 0.126 0.473 3 0.306* 0.085 0.001 0.133 0.479 4 0.306* 0.001 0.133 0.479 3 0.306* 0.001 0.133 0.479 4 0.079 4 0.079 4 0.079  - 0.167 0.180 4 - 0.042 0.085 0.628 - 0.215 0.132 3 1 - 0.306* 0.0850 0.001 - 0.479 - 0. 133 2 - 0. 006 0. 085 0. 941 - 0. 180 0. 167 4 - 0. 048 0. 085 0. 576 - 0. 221 0. 125 4 1 - 0. 258* 0. 085 0. 005 - 0. 431 - 0. 085 2 0. 042 0. 085 0. 628 - 0. 132 0. 215 3 0. 048 0. 085 0. 576 - 0.125 0.221 Note: Based on observed means. *: Difference in means is significant at the 0.05 level. 

3 Discussion 

Most of the existing endoscopic institutions in China use automatic irrigators (or pressure water guns) to flush the lumen of endoscopes to achieve a rinsing effect with the force of the liquid generated by the irrigator. However, the external surfaces of endoscopes are still rinsed using the traditional faucet rinsing method, which has problems of uneven distribution of water flow and pressure limitation, and is prone to high residual amounts of disinfectant on the external surfaces of endoscopes. Improving endoscopic cleaning methods to reduce OPA residue is a concern in clinical practice. The results of this study showed that the lowest OPA residue was found in the automatic cleaning and sterilising machine, followed by the spray tank, and the highest was found in the single stream, suggesting that the spray tank and the automatic cleaning and sterilising machine are more effective in removing OPA residue, probably because both of them use the principle of omni-directional pressure spraying to flush, whose flushing force and uniform distribution of the water flow are more effective in removing OPA. The cost of the spray wash tank is much lower than that of the automatic cleaning and disinfection machine, which meets the actual needs of clinical practice in China and is worth promoting its application. 

- 3611 - Chinese Journal of Sterilisation 

Chinese Journal of Sterilisation, Volume 33, Issue 12, 2016 Reasonable setting of the cleaning time to improve the cleaning efficiency The residual OPA on the surface of endoscopes is negatively correlated with the length of the cleaning process. The results of this study showed that when the cleaning time reached 2 min (volume = 20 L), the OPA residue tended to stabilise. This may be related to the fact that OPA can be absorbed by the endoscopic lumen itself as reported by Norman Miner et al [5]. 

It may be related to the fact that OPA can be absorbed by the polymerised material in the endoscopic lumen and persist, as reported by NormanMiner et al. Therefore, when endoscopic cleaning is performed in clinical practice, the longer the cleaning time, the better the effect of OPA removal. With reference to the results of this study, a reasonable setting of the endoscopic cleaning time can effectively remove OPA on the surface of endoscopes and improve the cleaning efficiency, thus increasing the turnover rate of endoscopes. Compared with the traditional disinfectant glutaraldehyde, the concentration of OPA is reduced, but direct contact can still cause damage to eyes, skin and mucous membranes [6].

6]. China's existing cleaning and disinfection standards do not specify the amount of disinfectant residue and cleaning process for endoscopes and other instruments [7], therefore, endoscopy institutions using OPA may not be able to use it.

7], therefore, endoscopy institutions do not pay much attention to chemical gastroenteritis and allergic reactions related to disinfectants. The results of this study confirm that insufficient cleaning will lead to increased OPA residue, so it is important to regulate the process of cleaning endoscopes and establish relevant standards and norms to improve the effectiveness of cleaning and disinfection and to protect the safety of patients. 

The proximity of the endoscope to the entrance makes it relatively easy for bacteria to enter the body, resulting in a high incidence of infection. The arterial end of the catheter has a lateral opening, which often leads to a high incidence of thrombus due to poor blood flow during the application process [4], and the process of handling thrombus also increases the chance of infection. In general, haemodialysis patients need to undergo dialysis two to three times a week, with an interval of at least 24 hours between dialysis sessions, during which the indwelling central venous catheter may be contaminated by bacteria, and ordinary disinfectant solutions do not have a long-lasting anti-bacterial effect after disinfection, which increases the risk of infection. The site and duration of catheter placement are the main factors affecting catheter infection, with femoral venous catheters being more susceptible to infection than jugular ones. The rate of catheter infection also increases linearly with duration of stay [5]. Chlorhexidine gluconate is the gluconate salt of chlorhexidine, which is a cationic surfactant and commonly used as a skin and mucous membrane disinfectant. It mainly destroys the permeability barrier of bacterial cell membranes, and at low concentrations it can lead to partial leakage of bacterial cytoplasm, while at high concentrations it can lead to coagulation and denaturation of the cytoplasm, so as to achieve the effect of killing bacteria [6]. Ethanol not only promotes the bactericidal effect of chlorhexidine gluconate and plays a synergistic effect, but also rapidly kills bacterial propagules, mycobacteria, fungal spores and lipophilic viruses, and has the characteristics of quick-acting and quick-drying, as well as the effect of sustained bacterial inhibition [7]. A large number of studies have shown that the incidence of infection of femoral vein indwelling catheters is higher than that of internal jugular vein [8]. The results of this study showed that there was no statistically significant difference in the infection rates between the femoral vein group and the internal jugular vein group when chlorhexidine gluconate was used for disinfection, while there was a statistically significant difference in the infection rates between the two groups when iodophor disinfectant was used. 

The incidence of infection in the femoral and internal jugular vein groups was not statistically significant, whereas the incidence of infection in the iodophor disinfectant group was statistically significant. This phenomenon may be due to the fact that chlorhexidine gluconate is more favourable to the maintenance of persistent local bacteriostasis. It has been reported in the literature that the incidence of infection increases with the duration of tube placement9, which is supported by the results of this study. However, the incidence of infection in the experimental group was significantly lower than that in the control group when the duration of catheter placement was longer than 2 weeks, suggesting that chlorhexidine gluconate can effectively reduce the incidence of catheter-related infections in haemodialysis patients due to prolonged central venous catheter placement. Therefore, chlorhexidine gluconate is more effective than povidone iodine in disinfecting central venous catheters and has good long-term antibacterial ability, which can effectively reduce the incidence of central venous catheter infections in haemodialysis patients, and it is worth to be popularized and applied in the clinic.