Karen Wernli, PhD

Dr. Karen Wernli asks: If deep sedation during colonoscopy raises your risk, is it worth the cost to wake up quickly?

by Karen J. Wernli, PhD, an assistant investigator at Group Health Research Institute

When you go in for a colonoscopy, you usually receive some type of anesthesia to help you manage the discomfort. These days, more people are receiving deep sedation with propofol for the colonoscopy, which lets them fall asleep rapidly—and quickly wake up. This clinical practice is fast being adopted, replacing standard moderate sedation, in which pain is lessened but the patient stays conscious—and takes longer to recover than with propofol. But no one really knows whether the use of deep sedation raises the risk of complications from the colonoscopy. 

A colonoscopy each decade is increasingly being used to screen for cancers of the colon and rectum in people starting at age 50. In a colonoscopy, a doctor uses a tube to examine the inner lining of the large intestine for tumors and polyps. Yearly stool tests are a noninvasive and more affordable alternative that has been proven effective for screening—and leads to fewer complications.

Others have shown that use of deep sedation in surgical centers is what is increasing the cost of colonoscopy overall. And the ever-rising number and cost of colonoscopies, in turn, have been blamed as one culprit in increasing costs of medical care in the United States.

How safe is this practice?

My colleagues and I were eager to discover how safe deep sedation is during colonoscopy. Colonoscopy carries its own (small) risks, independent of risks from anesthesia. With this new practice of deep sedation for colonoscopy, how do risks of 30-day complications from colonoscopy change? We looked at three kinds of risks: We expected to find an effect for risks associated with the colonoscopy procedure (like perforations) and with receipt of anesthesia (like complications due to the anesthesia); by contrast, for heart-lung risks (like stroke), we expected to find no effect with anesthesia services.

In research, size matters. Previous studies were too small to find rare outcomes, like the complications that we studied. To maximize our ability to draw conclusions, we examined a large set of claims data on more than 3 million colonoscopies nationwide in adults aged 40 to 64.

Overall, we found a link between use of anesthesia services (indicating deep sedation) and a 13 percent higher risk of any complication within 30 days: specifically, higher risk of perforation, bleeding, abdominal pain, complications due to anesthesia, and stroke. The risk of puncturing the wall of the colon was higher by 26 percent with anesthesia services only in those patients who had at least one polyp removed. This suggests one possible explanation: When patients are awake, they can tell the doctor that they feel undue pressure on the wall of the colon, thus preventing perforation; and when they are unconscious, they can’t give any feedback to their doctor.

Prevalence rising—and varied by region

We found that one in three colonoscopies were done with anesthesia services. And this proportion rose in each region in the United States during the period we studied—2008 through 2011—and is likely even higher now. Prevalence of anesthesia use during colonoscopy varied significantly by region: more than half in the Northeast; and less than one in 10 in the West. Use of anesthesia was lowest in Washington state. Unlike many settings, Group Health’s Group Practice does not routinely use propofol during colonoscopy, instead using moderate sedation. Group Health members’ information was not included in these claims-based data.

Risk of 30-day colonoscopy complications with anesthesia services also varied by region: In the Northeast, use of anesthesia was linked to a 12 percent rise in the risk of any complication; by contrast, in the West, it was linked to a 60 percent increase in risk. Future studies should attempt to confirm these results, while controlling for confounders, such as patient risk factors which might make them more likely to receive deep sedation during colonoscopy.

My coauthors are Carolyn M. Rutter, PhD, now at the RAND Corporation, but who worked at Group Health Research Institute for many years; Alison T. Brenner, PhD, now at the University of North Carolina, Chapel Hill, although earlier with the third coauthor, John M. Inadomi, MD, at the University of Washington (UW) School of Public Health’s Department of Health Services and the UW School of Medicine’s Division of Gastroenterology.

Support for our research came from the Agency for Healthcare Research and Quality (K12 HS019482 and 5 T32 HS 13853-9) and the National Institutes of Health (K24 DK080941 and U54-CA-163261).

Gastroenterology published our results as “Risks Associated with Anesthesia Services during Colonoscopy.”