Use of Bispectral Index Monitor (BIS) to Follow Depth of Sedation in Patients Undergoing Colonoscopy with Propofol Sedation

Abstract

Background: Sedation for gastrointestinal endoscopy is guided by patient responses to noxious stimuli. Differences in patient response to propofol occasionally result in instability due to oversedation. BIS is used to monitor depth of anesthesia by recording electroencephalographic data from the frontal cortex of the brain, which is predictive for intraoperative awareness. The objective of this study is to determine the ability of BIS to monitor sedation during colonoscopy. Materials & Methods: 45 patients were premedicated with midazolam (1-2 mg) and sedated with propofol. BIS readings were recorded at baseline, start, end, and minimum value. The same endoscopist performed all procedures. The endoscopist and an observer evaluated adequacy of sedation. Patients were asked to follow a simple command at the end of the procedure and again five minutes later. Any adverse outcomes were documented. Results: A statistically significant difference in the BIS score was noted between patients able to follow a command compared to those that were not at the end of each procedure (p<0.001). Patients with BIS values 30-60 at the end of the procedure took greater than 5 minutes to wake up, while those with values 58-90 woke up within one minute of the end of the procedure. BIS scores less than 70 were seen in patients requiring longer wake up times. Length of stay post-procedure in the endoscopy suite was longer in patients with longer wake up times. Predicted probability curves demonstrate that BIS values of at least 70 correlates with a 90% likelihood that the patient will be awake within 5 minutes of procedure completion with no procedural recall. There was a significant difference in BIS scores between baseline and all measured data points obtained during colonoscopy (p<0.001). Mean BIS values for baseline, procedure start, minimum, and end of procedure were 96, 65, 37, and 65 respectively. There were no adverse outcomes recorded. Conclusions: The BIS monitor may be used as part of a monitoring system during colonoscopy. Low BIS values correlate with deeper sedation and longer recovery times. BIS values between 54 and 76 appear optimal to avoid adverse events as well as over and under sedation. Use of the BIS monitor may allow improved titration of medication to shorten procedural recovery time, decrease procedure related costs and complications.