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The Value of Brain Monitoring with BIS
by Keith Candiotti, MD Dr. Keith Candiotti is Assistant Professor of Anesthesiology and Internal Medicine at the University of Miami where he serves as Chief of the Division of Perioperative Medicine, and Director of the Residency Program. Dr. Candiotti spoke to Aspect from his office in Miami. Aspect: Tell us about your first experience with the BIS monitor. KC: I was called on by an Aspect sales representative who offered to demonstrate the monitor and to leave one for us to use in the operating room (OR). Frankly, I wasn’t impressed at first because my sense was that the monitor's primary function was to prevent intraoperative awareness which, though serious, is very rare. I didn't really think I would have much use for it. Aspect: What changed your mind? KC: One day I found the BIS monitor lying around – at the time, no one was using it. I started using it on my own just to see what practical utility it might have. I noticed that in most cases where I used the BIS, I was using less anesthetic and patients were experiencing faster wake-ups. Aspect: How were you using the BIS? KC: We do a lot of back surgery here where we rely on IV infusions and nitrous oxide, without inhaled anesthetic. Relying only on vital signs such as blood pressure and heart rate was difficult. The BIS monitor allowed me to titrate my anesthetics to something more specific, the patient's hypnotic state. Initially, I used the BIS to confirm my independent clinical judgment about a patient's brain state. If the BIS displayed a value consistent with my clinical assessment, that was reassuring. If the BIS displayed a value at variance with my assessment, I could then re-evaluate other factors to affirm my own judgment or adjust the anesthetic. As I became more comfortable with BIS, I started titrating the anesthetic to a specific BIS value. I use it all the time now. Aspect: When you use the BIS monitor for teaching purposes with anesthesia residents, are you concerned that they may substitute reliance on the monitor for clinical judgment? KC: Anesthesia technique can be different with the BIS monitor, but we emphasize that the BIS can be a very helpful tool in directing anesthesia care. Rather than using the BIS just to measure response to anesthesia administration, we teach residents to titrate anesthetic to certain BIS values. But, we are careful to emphasize that BIS is not a substitute for clinical judgment, but a means for enhancing it. The BIS monitor is an excellent teaching tool in another respect. Let’s say you do fifty similar cases without BIS, and then begin doing them with the BIS. In my own experience the BIS monitor has taught me that in some types of cases I have been over-medicating patients. Since the BIS measures each patient’s individualized response to anesthesia and other factors, I have the comfort of knowing that patients who don’t fit the average profile will still get optimal anesthesia. Aspect: In your experience, how reliable is the BIS monitor? KC: Early on, about five years ago, there was more artifact in BIS readings, but artifact elimination has been significantly improved. Artifact isolation in all monitors is the optimal goal, but every monitor in the OR has artifact that results in occasionally erroneous numbers. That’s why we have doctors and not just monitors that control delivery of medical care. The BIS monitor has some useful features that help identify artifact such as the signal quality indicator which lets you know if there’s been corruption of the signal being sent to the monitor. The monitor also displays the EEG directly, so there are ways to confirm artifact that allow you to use BIS reliably. I also had an experience where the BIS number did not seem believable, but proved to be accurate. The patient turned out to have exquisite drug sensitivity. I had administered a very small amount of anesthetic and the BIS monitor indicated the patient was in an optimal plane of anesthesia. I doubted the reading at first, but in fact the patient was asleep. The elderly, for example, can be very sensitive to medication and BIS can be very helpful in preventing excessive anesthesia. Aspect: What’s the future for brain monitoring using BIS technology? KC: I believe brain monitoring will be the standard of care in anesthesia. How can you rationalize not using it? In the OR we monitor every major organ system except the one organ the anesthesiologist is most concerned about – the brain. We monitor the heart and the lungs, we monitor blood pressure, heart rate, urine output, and oxygen saturation – everything you can imagine, but the brain itself. The anesthesia community needs to understand that the BIS monitor is, simply, a brain monitor. If the patient is awake, it will show it. If the patient is asleep, it will show it. It is not an “awareness” monitor, or a recall monitor, just as the pulse oximeter is not a hypoxia monitor. The BIS monitor will alert you to brain states where awareness or recall may be an issue. It is a brain monitor, and in my experience, patients find it comforting to know that their brain state is being monitored. Once you start using the BIS monitor, its many benefits become apparent. |
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