Propofol vs. Midazolam-based Balanced Propofol for Nonanesthesiologist Moderate Sedation in Colonoscopy

Overview

Nonanesthesiologist administration of propofol for sedation is actually a field of growing interest for endoscopists, as demonstrated by recent American and European guidelines on this issue. Propofol is a hypnotic drug with rapid onset and offset of action. Used as a single agent, it is commonly titrated to deep sedation, whereas balanced propofol sedation (BPS), which combines propofol with small doses of a benzodiazepine and/or an opioid, can be successfully titrated to moderate sedation. However, nonanesthesiologists propofol administration remains controversial on account of the possibility of deep sedation/general anesthesia related adverse events. On the other hand, the use of longer elimination half-life drugs, such as opioids and benzodiazepines, may theoretically prolong sedation and recovery. Up to date, no study has addressed a head-to-head comparison of both regimens administered by non-anesthesiologists and titrated to moderate sedation. This study aims to evaluate the impact on propofol sedation of premedication with a fixed dose of midazolam (2 mg)2 minutes before propofol administration targeted to moderate sedation, in terms of depth of sedation, recovery times, safety and satisfaction. The onset of sedative action of midazolam has been reported to be 1-2.5 minutes and the peak effect of midazolam occurs 8-12 minutes. Taking into account that colonoscopy usually lasts a minimum of 15-20 minutes, our hypothesis is that synergy between propofol and midazolam may increase the depth of sedation through the initial phases of the procedure, diminishing propofol requirements, but not prolonging significantly recovery times.

Justification of the study: Nonanesthesiologist administration of propofol is controversial owing to deep sedation concerns. One of the latest therapeutic innovations on this issue has been the development of balanced propofol sedation, which consists of adding low doses of opioids or benzodiazepins. Several studies have recently demonstrated that BPS allows successfully moderate sedation, maintains a reversible drug component, reduces the total dose of propofol even by more than 50% without increasing adverse events and maintains high levels of physician and patient satisfaction, even for advanced endoscopic procedure. However, recovery may be prolonged by using midazolam or meperidine as they have a longer elimination half-life than propofol has. Up to date, nonanesthesiologist administration of propofol and BPS, using either midazolam or fentanyl, for outpatient colonoscopy have been compared in a single non-placebo controlled randomized trial (VanNatta and Rex, 2006). In this study, the authors obtained shorter recovery times with BPS compared to propofol alone, in contrast with the expected on account of pharmacokinetics. These results can be easily understood yet single-agent propofol was titrated to deep sedation, whereas BPS was titrated to moderate sedation. Therefore, it is necessary to make a randomized, double-blinded, placebo-controlled trial to directly compare both sedation regimens targeted to a similar moderate level of sedation. The results of this study will conclude which should be the first line treatment for moderate sedation in colonoscopy, providing further insight in drug synergy and its impact on the depth of sedation and recovery times