Research and experiments of a new premedication for improving mucosal visibility during esophagogastroduodenoscopy

Mucus and bubbles are important factors that can reduce endoscope visibility. This may result in missed diagnoses of minor or early lesions. Therefore, dimethicone, such as drugs used before esophagogastroduodenoscopy (EGD), is called premedication. There is no uniform premedication worldwide. Moreover, the clinical effects of existing preoperative medications cannot meet the needs of endoscopists.

The purpose of our study was to screen effective food additive components that can be used before EGD. In addition, we conducted in vitro and in vivo comparative experiments to evaluate the effectiveness of the compounds.

An in vitro foaming model was established to evaluate the function of food additives. Through preliminary experiments, we determined the lowest effective dose, ratio and application method of each main component. Two different levels of in vitro comparison experiments were designed. Egg white and water were mixed as foaming agents in the in vitro foaming model, whereas gastric juice was used in the in vitro gastric juice experiment. In vivo experiments were performed in a live rabbit model. We divided the samples into three groups: food additive 1 (papain) and food additive 2,3 (sucrose polyoxypropylene, polypropylene glycol) (group A), pronase and dimethicone (group B), and water alone (group C). In vitro experiments, the protein concentration difference and visibility difference suggest the ability of mucolytic agents, and the residual bubble amount and the minimum amount of defoamer required to suppress bubbles are the outcome measures for defoaming agents. The mucosal visibility score (MVS) is the outcome measure in experiments with live animals.

Three food additives were selected. Papain is a proteolytic enzyme, whereas sucrose polyoxypropylene and polypropylene glycol are defoamers. The lowest effective dose of papain was 500 mg. The optimal ratio of the two defoamers was 7:3, and the minimum effective doses were 116.7 mg and 50 mg, respectively. In the foaming model, the median protein concentrations differences of the three groups were 21.89 mg/mL, 21.54 mg/mL and 0.16 mg/mL. The visibility difference was 9.7 mL for group A and 4.1 mL for group B. The residual bubble amount of group A (0 mL) was significantly lower than those of group B (312.5 mL) and C (487.5 mL). The average minimum dose of defoamer used was 5.1 mL in group A. In group B, the foam could not be completely suppressed in four experiments, and in group C, ten experiments failed. In the gastric juice experiment, the median protein concentration differences between the two groups were 18.62 mg/mL and 17.33 mg/mL (P > 0.05). The visibility differences between the two groups were 5.65 and 4.00 mL (P = 0.017). Both groups A and B could completely eliminate the foam after the addition of 0.5 mL of different reagents. The minimum amount of defoamer needed to suppress bubbles in group A was slightly lower than that in group B (0.65 mL vs. 1.60 mL), but the difference was still not statistically significant (P = 0.155). In vivo experiments, the new premedication in group A could remove the mucus and foam completely compared with group B.The mean MVS decline rate of group A was significantly higher than that of group B (73.53% Vs. 39.39%, P < 0.05).

Proteolytic enzyme (papain) and two food defoamers (sucrose polyoxypropylene and polypropylene glycol) had superior effects on pronase and dimethicone. It may become a more effective preoperative medication regimen, but further research is needed.