To the Editor:

A recent change in practice amongst our gastroenterology colleagues prompts me to note this observation: gastrointestinal (GI) endoscopy is increasingly being performed with carbon dioxide (CO₂) as the insufflating gas. The reasoning is that the CO₂ is better absorbed by the body, resulting in less cramping, bloating, or other symptoms that reduce patient satisfaction, as well as a reduced risk of significant air embolism. While this has clear advantages for colonoscopy, it has produced unexpected consequences for some patients (and providers) during upper GI endoscopy.

There may be unpredictable reflux of CO₂ from the upper GI tract into the airway, producing artefactual elevations of end-tidal carbon dioxide (ETCO₂), an important component of ASA standard physiologic monitoring.¹ In at least one institution, this has led to the inappropriate administration of reversal agents due to an erroneous diagnosis of severe respiratory depression (ETCO₂ >80 mmHg). I find no reports of this artifact in either the gastroenterology or anesthesiology literature.

This artifact would, of course, not occur if the patient were intubated, as is frequently the case in longer procedures such as ERCP. However, in such prolonged cases, systemic CO₂ absorption may be significant, leading to a respiratory acidosis requiring extreme ventilatory measures. One of the original gastroenterology studies using general anesthesia set baseline ventilation at 15/min with a target ETCO₂ of 25 mmHg prior to insufflation. Even with this preemptive hyperventilation, arterial pCO₂increased up to 40% after 60 minutes of insufflation.²

I wish to draw attention to this increasing change in GI practice so that we may be more aware of the unintended consequences. Although CO₂ insufflation during endoscopy is relatively safe, the potential for both monitoring artifact during sedation and the risk of pCO₂ elevation (especially in compromised patients) is worthy of more discussion.

James Berry, MD
Vice-Chair for Faculty Affairs
Department of Anesthesiology and Pain Management
UT Southwestern Medical Center
Dallas, TX

The author has no relevant disclosures to report.

References

1. ASA Standards for Basic Anesthetic Monitoring, October 28, 2015; at http://www.asahq.org/quality-and-practice-management/standards-and-guidelines.
2. Suzuki T, Minami H, Komatsu T, et al. Prolonged carbon dioxide insufflation under general anesthesia for endoscopic submucosal dissection. Endoscopy 2010;42:1021-1029.