Prevention of White Flocculate Precipitation with Simethicone During Upper Gastrointestinal Endoscopy: A Double‐Blinded, Multi‐Center, Randomized Study


 Background: The reformulated simethicone emulsion from Berlin Chemical AG might develop white flocculate precipitation covering gastric mucosa when used before esophagogastroduodenoscopy (EGD). We aim to investigate whether combining reformulated simethicone emulsion with 5% NaHCO3 solution could prevent the development of white precipitation and improve visibility during EGD. Methods: Our study involved 523 patients. They were randomly assigned to two groups: In Group A patients received a warm mixed solution containing 30 ml 5% NaHCO3 solution and 15 ml reformulated simethicone emulsion. In Group B patients received 45 ml 40℃ lukewarm water. Visibility scores were recorded and analyzed. In addition, flush times, volume of flush water, overall time taken for EGD and complications during or after procedure were also recorded. Results: We found that no white precipitation was observed during EGD in Group A. Moreover, visibility scores in Group A were significantly lower (P < 0.01). Patients in Group A had fewer flush times (P < 0.01) and smaller volumes of flush water (P < 0.01). In addition, overall time taken for EGD procedure was significantly shorter in Group A (P < 0.01). The percentage of patients who had no adverse response is significantly higher in patients in Group A compared to Group B (P < 0.01). Conclusions: Premedication with mixed solution of 15ml reformulated simethicone emulsion and 30ml 5% NaHCO3 solution can prevent the development of white precipitation, substantially enhance mucosal visibility safely.Trial registration: The registered name of the trial is “Efficacy of using premedication with reformulated simethicone emulsion during upper gastrointestinal endoscopy examination”. Current Controlled Trials ChiCTR1900021689, as well as the date of registration is 11 September 2019. Retrospectively registered, http://www.medresman.org.cn/uc/sindex.aspx.


Background
Esophagogastroduodenoscopy(EGD) is the most important method for diagnosing upper gastrointestinal disease [1]. High-quality EGD examination will signi cantly increase the diagnostic rate for upper gastrointestinal disease, especially for early or subtle lesions.
The major technical obstacle lies in the presence of foam and mucus over gastric mucosal surfaces which often results in impaired visibility, prolonged examination time, aggravating discomfort for patients and even increasing missed diagnosis rates of early or subtle lesions. Published data from institutions in the United Kingdom have shown that 10-14% of gastric cancer patients had undergone EGD in the preceding 3 years [2,3]. Impaired visibility may be a paramount factor for missing diagnosis of EGD [4].
Thus, the elimination of foams and mucus over gastric mucosa is essential before endoscopic examination. It is generally accepted that premedication with antifoam/mucus agent before EGD can improve operation visibility [5][6][7]. Premedication with pronase [7][8], N-acetylcysteine [9] or simethicone [4] before EGD improves procedural visibility. In addition, combining different antifoam/mucus agents might be more effective [4]. Premedication before EGD with sedation has proven to be safe [7]. Nevertheless, the optimal quantity, density and time of premedication have not yet been established.
For this reason, in East Asian countries especially Japan, premedication with an antifoam/mucus agent before EGD has become a standard procedure [6]. However, there is insu cient evidence that premedication with antifoam/mucus agents before EGD can improve the detection rate of early or subtle lesions. The safety of antifoam/mucus agents also remains to be clari ed, which may be the essential reason why it has yet to be widely utilized in the west. The ideal antifoam/mucus agent should have nontoxic side effects, strong tolerance and wide adaptation for different patients [10].
Among the variety of antifoam/mucus agents put into use nowadays, simethicone is the most common option for endoscopy [7]. It is effective in eliminating foam and mucus by decreasing the surface tension of bubbles or foam [11]. Moreover, simethicone was proven effective in improving mucosal visibility when used as a premedication for EGD [4]. The latest Asian consensus on standards of diagnostic upper endoscopy for neoplasia has strongly recommended premedication with simethicone before EGD, classifying it as a level A recommendation [12].
Berlin Chemical AG, Germany, is the largest producer of simethicone emulsion in the world. To improve the stability of the product, the company's formula was optimized and upgraded in October 2016. The reformulated simethicone emulsion has been replaced raw materials to make the product more stable. Compared to the original product, the reformulated simethicone emulsion is better in the following three aspects: 1. the surface changes from emulsion into a milky liquid with low-viscosity; 2. shelf life is 6 months instead of 28 days; 3. the emulsion can be preserved at room temperature rather than 25 ℃. Overall, the reformulated simethicone emulsion is more stable. However, it is found that the reformulated simethicone emulsion might develop a small amount of white occulate precipitation covering gastric mucosa when used before EGD, which will impair the observation of endoscopy. To eliminate the white precipitation, some endoscopists adopted NaHCO 3 mixed with reformulated simethicone emulsion as premedication before EGD. In our laboratory studies, it was found that premedication with 5% NaHCO 3 solution combined with reformulated simethicone emulsion could eliminate white precipitation effectively under acidic conditions. However, there is no evidence-based data on the optimal usage method and dosage of NaHCO 3 in patients. Therefore, we have been endeavoring to create a standard recommendation for the usage of NaHCO 3 in combination with reformulated simethicone emulsion prior to EGD.
The present study aims to determine whether premedication with reformulated simethicone emulsion combined with NaHCO 3 can prevent the development of white precipitation and substantially improve mucosal visualization in upper gastrointestinal endoscopy examination. We have also examined its safety and effectiveness in reducing the time taken for the procedure.

Vitro Experiment
The experiment was based on the theory that the average volume of fasting gastric acid is 50 ml and the theoretical maximum volume of gastric acid is 100ml [13]. Hydrochloric acid solution with a pH of 1.04 con gured with concentrated hydrochloric acid was used to simulate gastric acid. We reduced gastric acid volume, simethicone emulsion and NaHCO 3 dosage to 1/5 respectively in our vitro model experiment. The following procedures were performed: Add different volumes of 5% NaHCO 3 solution into 3 ml simethicone emulsion and shake the mixtures well. Then add the mixed solutions into the centrifugal tubes containing 10 ml arti cial gastric acid to observe the stability of simethicone after 0 min, 15 min, 45 min, 60 min and 240 min, respectively. Meanwhile, measure the pH value at the reaction endpoint. The above operation was also performed with 20 ml arti cial gastric acid.

Patients
The study was conducted in six hospitals simultaneously.

Premedication And Endoscopic Procedure
Patients were randomly assigned to two groups (A: B allocation ratio was 2:1) by random computergenerated numbers before the endoscopy procedure. A total of 535 patients were enrolled in the study. Twelve patients were excluded in accordance with the exclusion criteria: ten patients had a history of upper gastrointestinal surgery and two patients didn't meet the age criteria. The endoscopists and nursing staff were blinded to the medications administered before EGD. In Group A patients received warm mixed solution containing 30 ml 5% NaHCO 3 solution and 15 ml reformulated simethicone emulsion (Berlin-Chemie AG, Berlin, Germany) 30 min before EGD. In Group B, patients received 45 ml 40℃ lukewarm water 30 min before EGD. Patients in both groups were instructed to walk back and forth 3 times within the prescribed 10-metre area. All patients received 10 ml lidocaine hydrochloride mucilage 10 min before the endoscopy procedure. Nurses completed the whole premedication procedure so that patients were blinded to the premedication used.
Endoscopists, who have 5 or more years of experience, performed the conventional EGD during which patients underwent the whole procedure without sedation and anesthesia. At the same time, a nurse was assigned to record the related data during and after EGD for subsequent analysis. The endoscopists and nurses who completed the operation were unaware of the group differentiation.
The whole operation was recorded. After the procedure an experienced endoscopist in each hospital, who had not participated in the examination, reviewed the endoscopic videos and images. Both the endoscopists who performed the procedures and the participants of EGD remained blinded to the premedication drugs used during the study. Firstly, it was evaluated whether white precipitation developed (Fig. 1). Subsequently, each patient was analyzed based on the following criteria. The primary criterion was mucosal visibility. Visibility scores of esophagus, gastric fundus, gastric body, gastric antrum, gastric angle and duodenal mucosa were then reported respectively. The scoring system is shown in Fig. 2: score 1, indicating no adherent mucus and clear view of the mucosa; score 2, a thin coating of mucus but no obscured vision; and score 3, adherent mucus obscuring vision [14]. The sum of the scores of each site adds up to the nal score. The secondary criteria included the detection rate of visual lesions, time taken for the whole procedure, amount of saline water consumed for mucosal cleansing and adverse reactions during or after the procedure. A ow chart of the present study is shown in Fig. 3.

Statistical analysis
Our study considered the study power as to be 90% and determined the type I error as 0.05, and also set the minimum expected difference in visibility scores between the two groups as 0.15, according to the previous data [15], assumed 15% for missing probability. In the actual experimental research, a total of 523 patients were included in the study.
Acquired data were interpreted as means ± standard deviation (SD) or numbers (%). Continuous variables were assessed by Student's t-test while categorical variables were tested by chi-squared test or Fisher's exact test. P < 0.05 was considered statistically signi cant. Statistical analysis was carried out with SPSS 22.

Results
Investigation of stability of reformulated simethicone emulsion mixed with different doses of NaHCO 3 solution under acidic condition in vitro It was found that when the pH of reaction endpoint was higher than 5.5, there would be no white precipitation in the vitro experiment (Appendix 1; Appendix 2). In 10 ml of arti cial gastric acid, at least 3 ml of 5% NaHCO 3 solution mixed with 3 ml of reformulated simethicone emulsion was needed to prevent the development of precipitation (Appendix 1). In 20 ml of arti cial gastric acid, at least 5 ml of 5% NaHCO 3 solution mixed with 3 ml of reformulated simethicone emulsion was needed to prevent the development of precipitation (Appendix 2). Based on the theory that the average volume of fasting gastric acid was 50 ml and the theoretical maximum volume of gastric acid was 100 ml, the mixed solution containing 30 ml 5% NaHCO 3 and 15 ml reformulated simethicone emulsion was chosen to conduct clinical research.

Demographic Characteristics Of Patients
A total of 535 patients were identi ed and enrolled into the study, out of which twelve patients were excluded; therefore, 523 patients were included in the nal analysis (Fig. 3). There was no statistical difference between the demographic characteristics of the two investigated groups. There was also no difference in referral category or clinical indication between the two groups (Table 1).  The in uence of premedication with reformulated simethicone emulsion and 5% NaHCO3 solution on the ush times and volume of ush water during EGD There were signi cant differences between the ush times for clearing stubborn mucus or bile in the two groups (Table 3). Signi cantly less time was required in Group A compared to Group B (P < 0.01), in terms of gastric fundus, gastric angle, gastric body, gastric antrum, duodenum and total time. The volume of water needed to ush the esophagus, gastric fundus, gastric angle, gastric body, gastric antrum, duodenum and in total were both signi cantly less in Group A compared to Group B (P < 0.01).  Figure 4 shows the mean overall time for all gastroscopies in Group A (5.73 ± 2.65 min) was shorter than in Group B (6.76 ± 3.13 min). The difference between the two groups (P < 0.01) was signi cant.
The complications of premedication with mixed solution of reformulated simethicone emulsion and 5%

NaHCO3 solution
The incidence percentage for abdominal pain (0.8% vs 4.1%, P < 0.05) and distension (5.4% vs 19.5%, P < 0.01) during EGD were signi cantly higher in Group B than they in Group A (Fig. 5a). There was no signi cant difference between Group A and Group B for the percentage of patients who had no adverse response (57.6% vs 55.0%) and nausea (34.5% vs 29.6%) during EGD.
The incidence of abdominal pain (10.1% vs 1.7%), distension (9.5% vs 6.5%) and nausea (2.4% vs 1.7%) after EGD occurred signi cantly more often in Group B than in Group A (P < 0.01) as shown in Fig. 5b. In addition, the percentage of patients who had no adverse response (82.8% vs 77.5%) is signi cantly higher in Group A (P < 0.01).

Discussion
Foams and bubbles can impair the detection of small and early lesions in EGD. Flushing during operation may result in longer procedure time and increase the risk of adverse reactions. Proper preparation can lower the need to ush the mucus during the procedure. It is widely accepted that premedication with an antifoam/mucus agent can improve endoscopic visibility during EGD [9]. Thus, the usage of antifoam/mucus agents before EGD may improve acceptance for patients. Simethicone has been used as an effective antifoam/mucus agent [15]. Recently, the Berlin Chemical AG modi ed the formula of simethicone emulsion. The clinical data showed that a small amount of white occulate precipitation still existed during EGD after premedication with the reformulated simethicone emulsion. In some hospitals, it was recommended that patients take NaHCO 3 before the new simethicone emulsion. However, further evidence-based research is needed to carry out to determine the optimal method of administration, dosage, of NaHCO 3 with reformulated simethicone emulsion. The present study is the rst trial to investigate the effectiveness and safety of a mixed solution containing reformulated simethicone emulsion and NaHCO 3 prior to EGD.
In our laboratory experiment, it was observed that a NaHCO 3 solution combined with reformulated simethicone emulsion could prevent the development of white precipitation by neutralizing arti cial gastric acid. The results showed a mixed solution containing at least 5 ml 5% NaHCO 3 solution and 3 ml reformulated simethicone emulsion was needed for maintaining the stability of simethicone in 20 ml arti cial gastric acid. Therefore, in clinical research, the mixed solution containing 30 ml 5% NaHCO 3 solution and 15 ml reformulated simethicone emulsion was adopted as premedication before EGD according to the theoretical maximum volume of gastric acid (100 ml) [13].
Mucosal visibility is paramount in detecting subtle and early lesions during diagnostic EGD [16]. This study showed that premedication with mixed solution of reformulated simethicone emulsion and 5% NaHCO 3 solution could prevent the development of white precipitation during EGD, substantially enhancing mucosal visibility in Group A compared to the control group. In study of Suvakovic et al. [17], they analyzed 181 advanced gastric cancer patients and found that 11.2% had undergone gastroendoscopy. It is likely that a number of reasons are to blame for the missed diagnosis of EGD, among which patient preparation is an assignable factor. To a large extent the quality of preparation before EGD in uences the quality of the operation. Proper preparation may help to decrease the missed diagnosis rate of EGD. Mucosal visibility, a core factor to evaluate the quality of EGD, is in uential in the detection of lesions. Some previous studies showed that N-acetylcysteine or Pronase combined with simethicone could improve mucosal visibility [4,9]. However, the increased cost is too signi cant to be ignored and NaHCO 3 solutions costs much less. Premedication of emulsion simethicone and NaHCO 3 solution requires only increases costs a little. The unit price of emulsion simethicone and NaHCO3 solution (100 ml) are 48 RMB and 1.6 RMB, respectively. Compared with using simethicone alone, this combination only costs an extra 1.6 RMB. Hence, reformulated simethicone emulsion combined with NaHCO 3 solution is a potential novel and highly e cient premedication for EGD. In addition, improved mucosal visibility may contribute to early diagnosis of gastric diseases including gastric neoplasm. Early gastric cancer patients have excellent future survival rates and quality of life. Sue Ling et al. reported the 5 year survival rate for patients who were diagnosed with gastric cancer early reached 98% [18] Whereas the prognosis of advanced stage detection is dismal [19]. Moreover, the majority of early diagnosis is opportunistic [20] Thus, high quality EGD is vital for diagnosis and prognosis of gastric cancer.
The study results also found the numbers of ush times and the volumes of ush water used in most areas decreased in patients who accepted premedication with mixed solution. There is also a good evidence of improved mucosal visibility in Group A. As can be seen from the data, there is no signi cant difference between Group A and Group B in terms of the ush times for the esophagus. A possible explanation is that most mucus and foam in esophagus can be eliminated through aspirating, but not ushing. This study observed a signi cantly shorter operation time for EGD in Group A as well. Similarly, the study done by Lee et al. [14] found that it took signi cantly less time to complete EGD in patients receiving simethicone and Pronase before operation. However, the time required for EGD procedure was signi cantly longer in the premedication group than in the control group in Zhang's study. [7]. They suggested observing suspicious areas to and allowing more time for the ingestion of retention liquid before EGD [7]. Comparatively, the results in our present study may be due to enhanced mucosal visibility and fewer ush times, therefore more suspicious areas can be observed more easily. Most endoscopic examinations are not under sedation in China, hence shorter procedure time can reduce discomfort for patients, which then will contribute to higher satisfaction of EGD and avoiding delayed diagnosis of gastric cancer [9].
EGD is an invasive operation. Many patients refuse it for fear of discomfort. In addition, some rare complications may lead to surgical operation. In Japan and other East Asian countries premedication before EGD is routine. Despite this, there is little evidence of the safety of using premedication before EGD in Western countries [16]. Our study investigated the safety of premedication that included reformulated simethicone emulsion combined with NaHCO 3 solution. The result showed that the percentage of patients who had no adverse response is signi cantly higher in patients who had received premedication before EGD. The incidence of abdominal pain and distension were signi cantly less in Group A whether during or after EGD. The percentage of patients who had nausea after EGD is also lower in Group A. It was indicated that premedication with mixed solution containing reformulated simethicone emulsion and NaHCO 3 solution could reduce complications. Simethicone is commonly used for gas and distension [21].
It contributes to the relief of symptoms caused by the injection of gas during EGD. Besides, fewer ush times and smaller volumes of ush water result in less discomfort, which may reduce complications during and after operations.
There are still some limitations in the study. We cannot cite published data showing that the reformulated simethicone actually causes worse visualization when used as premedication before EGD. Additionally, we did not present the pathological information. The ability to detect diminutive lesions or early lesions is vital for the diagnosis of gastric cancer. However, it will take a long time to follow up with a large enough number of patients to acquire conclusive results. In-depth investigation will be done in the future.
Our research is the rst multicenter prospective double-blind randomized controlled study to show the effectiveness and safety of premedication with mixed solution of reformulated simethicone emulsion and 5% NaHCO 3 solution before EGD. The results showed reformulated simethicone emulsion combined with 5% NaHCO 3 solution can prevent the development of white precipitation, markedly enhance mucosal visibility. In addition, it is proven to be safe and can reduce complications. As there is no standard recommendation or guidelines for premedication with reformulated simethicone emulsion and NaHCO 3 solution so far, we recommend the routine use of premedication with mixed solution of 15 ml reformulated simethicone emulsion and 30 ml 5% NaHCO 3 solution 30 min before EGD.

Conclusion
The reformulated simethicone emulsion might develop white occulate precipitation covering gastric mucosa when used before EGD. Premedication with mixed solution of 15 ml reformulated simethicone emulsion and 30 ml 5% NaHCO 3 solution can prevent the development of white precipitation, substantially enhance mucosal visibility safely. Abbreviations esophagogastroduodenoscopy EGD standard deviation SD Declarations Ethics approval and consent to participate The experimental protocol was established, according to the ethical guidelines of the Helsinki Declaration and was approved by the Human Ethics Committee of Sir Run Run Shaw Hospital a liated to Zhejiang University. Written informed consent was obtained from individual or guardian participants.

Consent for publication
Not applicable.
Availability of data and material All data are fully available without restriction.

Competing interests
The authors declare that they have no con ict of interest.