Is sedation really to blame?

We have read with interest the Austrian Colorectal Cancer screening experience [1]. An interesting finding of this study was the possible association between perforation and procedural sedation. Although it is difficult to estimate the effect of sedation in such relevant but rare events, the best evidence available to date does not support this hypothesis [2] [3].

The authors state that sedation increased the risk of complications (P  = 0.03; 95 % confidence interval 1.05 – 2.17) and that all 20 perforations occurred in sedated individuals. However, this causal relationship is not supported by the study design, which allows us to state only that there was a modest association at best. We believe that several factors should be considered when interpreting these results:

1. What type of sedation was used the most? (moderate/deep and anesthesiologist/nonanesthesiologist administered);

2. Were there differences between the sedated and unsedated groups? (specifically, in age, co-morbidities, lesion number/morphology, and predictors of difficult colonoscopy);

3. Did the perforations occur as the result of polypectomy or insertion? (to evaluate the effect of sedation one should exclude polypectomy-associated perforations).

In addition, we know that sedation was administered in 87.2 % (n = 138 863) of the colonoscopies. With a perforation incidence of 0.01 %, one would expect 2 – 3 perforations in the 20 383 unsedated individuals. Therefore, the observed incidence (n = 0) in the unsedated group is close to the expected range (P  = 0.10).

Also, the most commonly reported complication was bleeding, which is not explained by sedation and may be the effect of an uncontrolled confounder.

This is a relevant study and despite understanding that sedation was not the main intervention under analysis, we believe it is important to clarify these aspects.

• References

• 1 Waldmann E, Gessl I, Sallinger D. et al. Trends in quality of screening colonoscopy in Austria. Endoscopy 2016; 48: 1102-1109
• 2 Cooper GS, Kou TD, Rex DK. Complications following colonoscopy with anesthesia assistance: a population-based analysis. JAMA Intern Med 2013; 173: 551-556
• 3 Vargo JJ, Niklewski PJ, Williams JL. et al. Patient safety during sedation by anesthesia professionals during routine upper endoscopy and colonoscopy: an analysis of 1.38 million procedures. Gastrointest Endosc 2017; 85: 101-108