Difficult sedation is an uncommon but challenging and poorly understood part of gastrointestinal endoscopy. Although much about the phenomenon isn't known, it is clear that difficult sedation can increase patient discomfort, lead to incomplete or aborted procedures, and squander time and resources.
Although a few studies have tried to identify predictors of difficult sedation, most are compromised by the failure to use validated tools. And some factors anecdotally associated with hard-to-sedate patients, such as physical and sexual abuse, have never been investigated.
This led researchers at Washington Hospital Center in Washington, D.C., to take a more rigorous and comprehensive look at the relationship between difficult sedation and factors such as alcohol and drug use, anxiety, and physical or sexual abuse.
Michael D. Crowell, Ph.D., of Mayo Clinic in Arizona, designed the study and served as biostatistician, working closely with lead investigator Kevin W. Olden, M.D., now of St. Joseph's Hospital and Medical Center in Phoenix.
Dr. Crowell explains, "We felt there were a few articles and a lot of clinical recommendations about what may contribute to difficult sedation, but not a lot of good data based on validated instruments. We wanted to address that question more directly and in a more systematic way."
For the prospective cohort study, researchers recruited 180 patients from Washington Hospital Center's gastroenterology and colorectal surgery outpatient clinics between February 2010 and November 2010. Of those enrolled, 143 completed the study.
At the time of enrollment, each participant completed three validated questionnaires:
The day of the procedure — either colonoscopy or esophagogastroduodenoscopy —patients received a combination of intravenous midazolam and fentanyl or meperidine. After the test, the attending gastroenterologists recorded the difficulty of sedation using the Richmond Agitation-Sedation scale (RASS), a validated tool for assessing conscious sedation.
Based on the RASS score, 56 patients (39 percent) were judged difficult to sedate. After adjusting for gender, these patients were nearly three times more likely to have both increased trait and state anxiety than were patients with normal sedation.
Psychotropic drug use was also associated with difficult sedation, but researchers warn that this finding should be interpreted cautiously because of the small number of patients taking these medications.
Unlike other research, the study did not show an association between alcohol abuse or chronic narcotic use and difficult sedation, but again, researchers say the results should be viewed carefully because only a few of those in the study met the criteria for substance abuse.
Even more surprising, researchers saw no association between sexual or physical abuse and hard-to-sedate patients, although they had expected to find one.
Dr. Crowell makes several important points. First, he notes that the concept of difficult sedation covers a lot of territory, ranging from a patient who doesn't feel sleepy after sedation to one who is uncooperative, aggressive or belligerent. In all circumstances, the general protocol is to add more medication.
"The problem," he says, "is that some studies define difficult sedation by doses of sedating drugs given. But there is a lot of bias in that because some endoscopists will give a lot more medication up front to avoid any of that happening, so then, really, you're just measuring the amount of medication given."
By contrast, Washington Hospital researchers used the RASS scale to objectively describe difficult sedation based on precise definitions for different levels of sedation and agitation.
Dr. Crowell concludes, "The takeaway message of our study is generally common knowledge: Anxious patients do less well with conscious sedation. And if we recognize that it is not so much alcohol or narcotics or an abusive history but rather anxiety and psychotropics that make endoscopy more difficult, then we can take a different approach with these patients. We can be more reassuring or even provide some intervention before the procedure to help reduce anxiety, which may provide a better experience for them."
He adds that relieving anxiety in endoscopy patients can have institutional benefits, too.
"If we can reduce the number of difficult-to-sedate patients, then we will likely also reduce the number of overly long, canceled or aborted procedures," he says.