Abstract: Objective To verify that the administration of sodium bicarbonate solution before gastroscopy can have comparable defoaming effects as the commonly used defoaming medications in clinical practice without affecting the detection rate of endoscopic lesions. Methods In this double-blind, single-center, randomized controlled trial, 950 patients undergoing gastroscopy were involved, who were randomly assigned to 6 groups. A, B, and C were experimental groups, while D, E and F were control groups. In group A, 1 g of sodium bicarbonate was dissolved in 50 mL of warm water at 40 ℃; in group B, 2 g of sodium bicarbonate was dissolved in 50 mL of warm water at 40 ℃; in group C, 1 g of sodium bicarbonate+3 mL of simethicone was dissolved in 50 mL of warm water at 40 ℃; in group D, 20 000 U of pronase(containing 1g of sodium bicarbonate)+3 mL of simethicone was dissolved in 50 mL of warm water at 40 ℃(the fixed gastroscopy premedication in our center); in group E, 1.2 g of N-acetylcysteine(NAC)+3 mL of simethicone was dissolved in 50 mL of warm water at 40 ℃; in group F, 50 mL of warm water at 40 ℃ was used. All patients routinely drank 10 mL of lidocaine gastroscopic lubricant to anesthetize the pharynx 5 min before the procedure. After completion of the examination, the operating physicians filled in a rating form for the mucosal visibility score(MVS)and operational satisfaction score(OSS), recorded the endoscopic diagnosis, and calculated the total mucosal visibility score(TMVS). Results Group F was the least effective in removing blisters; only 2% of the patients had TMVS of 5 and only 71% achieved physician satisfaction, significantly lower than those of the other 5 groups; the differences in scores for each site and physician satisfaction were statistically significant compared to the other 5 groups(P<0.003). Group D was the most effective in removing blisters; 70% of the patients had TMVS of 5, and 98% achieved physician satisfaction. Groups A and D had comparable effects in removing blisters; there was only difference in TMVS(P<0.003). There was only significant difference in MVS of gastric fundus between group A and group C(P<0.003). There were differences in the MVS of gastric fundus, gastric body and TMVS between group C and group D(P<0.003). The overall efficacy of defoaming in Group C was average. Between group A and group B, the differences in all scores were statistically significant(P<0.003), and the efficacy of foam removal was significantly better in group A. No statistically significant differences in all scores were observed among groups E, A and C, and the efficacy of foam removal was approximately the same. There was no significant difference in the detection rate of endoscopic lesions among the 6 groups(P>0.003). Conclusion Administration of 1 g of sodium bicarbonate solution before gastroscopy can achieve approximately the same efficacy as the commonly used defoaming medications without affecting the detection rate of endoscopic lesions. The administration of 1 g is more effective than 2 g, and the addition of simethicone may not yield better results. Sodium bicarbonate is inexpensive and worth promotion in primary hospitals.

Key words: Sodium bicarbonate, Simethicone, Gastroscopy, Premedication, Detection rate