Impact of carbon dioxide insufflation and water exchange on postcolonoscopy outcomes in patients receiving on-demand sedation: a randomized controlled trial

      Background and Aims

      Water exchange (WE) is the least painful insertion method during colonoscopy. Its impact on postcolonoscopy discomfort has not been well-described. Carbon dioxide (CO2) insufflation consistently reduced postcolonoscopy discomfort. We compared postcolonoscopy outcomes of various combinations of insertion and withdrawal techniques (insertion-withdrawal modality): WE-CO2, WE-air insufflation (WE-AI), and CO2-CO2.


      A total of 240 patients undergoing on-demand sedation diagnostic colonoscopy were randomized to WE-CO2 (n = 79), WE-AI (n = 80), CO2-CO2 (n = 81), with postprocedural data collected up to 24 hours. The primary outcome was postcolonoscopy bloating. Other postcolonoscopy outcomes included pain scores, flatus and incontinence episodes, toilet use, interference with normal activities, patient satisfaction, and patient willingness to repeat the procedure.


      Demographic and procedural data were comparable. Compared with WE-AI, WE-CO2 and CO2-CO2 resulted in significantly less bloating (all P < .0005) and lower pain scores (P values ranged from .008 to < .0005) up to 3 hours and fewer flatus episodes up to 6 hours (P values ranged from .003 to < .0005). WE-CO2 resulted in less interference with same-day activities compared with WE-AI (P = .043). The differences in postprocedural outcomes were significant, but the magnitude was small. Patient satisfaction and willingness to repeat the procedure were high and comparable among groups. WE was the least painful insertion technique (P < .0005).


      The combination WE-CO2 appears to be the optimal choice to decrease pain during the examination and to reduce bloating and other undesired procedural outcomes afterward. If a CO2 insufflator is already available, it seems advisable to adopt the combination WE-CO2. In the absence of a CO2 insufflator, the cost effectiveness of the addition of withdrawal CO2 to WE in diagnostic and nondiagnostic settings needs to be critically assessed. (Clinical trial registration number: NCT02409979.)


      AI (air insufflation), ANOVA (analysis of variance), CO2 (carbon dioxide), CO2-CO2 (carbon dioxide insertion with carbon dioxide withdrawal), NRS (numeric rating scale), WE (water exchange), WE-AI (water exchange insertion with air insufflation withdrawal), WE-CO2 (water exchange insertion with carbon dioxide withdrawal)
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