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Anesthesia Alert
5 Good Reasons to Monitor Anesthetic Depth
David Barinholtz
Publish Date: September 4, 2008   |  Tags:   Anesthesia

It's been 12 years since the FDA approved the first neurophysiologic monitor for the purpose of assessing anesthetic depth, and yet a great deal of controversy still surrounds this technology, with about half of anesthesia providers embracing routine monitoring and the other half just as passionately rejecting it.

Much of the controversy has to do with claims that brain monitoring can reduce the risk and incidence of intraoperative awareness, an important issue that unfortunately became sensationalized in the media around the time the first monitors were hitting the market. Studies on the effectiveness of brain monitoring in preventing awareness yielded mixed results, which did little to support those claims. But in focusing solely on the awareness issue, you might be missing the other, far more significant benefits of this technology. I use a brain monitor on every one of my outpatient surgery cases, most of which involve deep sedation/general anesthesia with propofol in combination with other intravenous agents. Even if you don't buy the argument that monitoring prevents intraoperative awareness, here are five good reasons to routinely monitor patients' brain activity under anesthesia.

Reduced drug usage (and I pay for my own)
The heated debate over awareness prevention tends to obscure the primary benefit of depth-of-anesthesia monitoring: increased efficiency. That's the No. 1 reason to use the technology. Unlike many of my colleagues, I pay for all my own drugs, and I'm responsible for staying on the premises with patients until they're awake and out the door. I've been using depth-of-anesthesia monitoring for nearly 10 years, and I've found it to be instrumental in helping me do my job much more efficiently.

The key to realizing this goal is to titrate the amount of drugs you use to keep a patient anesthetized according to the depth of anesthesia indicated by the monitor. Although the American Society of Anesthesiologists hasn't designated it a standard of care, I've found brain monitoring to be a much more accurate indication of the depth of anesthesia than blood levels. Just as 100 people with the same blood alcohol content will display many different levels of drunkenness, 100 patients with the same blood level of a given anesthetic will show many different levels of cortical activity.

Having a more accurate picture of how asleep your patients are lets you use just the right amount of anesthetic agents to keep them at that level, without overdoing it. In more than 10 years of brain monitoring in my practice, we've experienced a 30-percent drop in propofol induction doses and a 20-percent decrease in maintenance infusion rates for longer procedures (30 minutes or more) using multiple intravenous agents. Given the large expense associated with anesthetic drugs, it's clear that the significant reduction in dosage during longer procedures translates to a huge cost savings.

Fewer adverse effects
Using less drugs — or, more accurately, just the right amount of drugs — to keep patients asleep during surgery has several correlating benefits. One is reducing such post-op side effects as nausea and vomiting. Before we began using brain monitors, the PONV rate among our patients using TIVA was about 10 percent to 15 percent; we've been able to get that PONV rate down to about 1 percent to 2 percent. In the same period, we also switched our PONV prevention regimen from a one-two drug combination to a multi-modal PONV prophylaxis, depending on each patient's PONV risk factors. The reduction in side effects was probably due to a combination of both factors — brain monitoring and multi-modal prophylaxis — but studies have shown that depth-of-anesthesia monitoring alone can reduce PONV (Liu, 2004, Anesthesiology; Chan et al., 2005 ASA meeting).

Faster wake-ups and discharge
The correlation between using less drugs and getting patients conscious and alert quickly is obvious. Our average patient is awake within two to five minutes after her procedure is complete, and more than 90 percent of patients enter PACU with an Aldrette score of 9 or greater, meaning they're already in Phase 2 recovery, are more awake and alert, and require less nursing care and time spent in recovery. Virtually all our patients spend less than an hour in PACU, even those who've undergone longer procedures under general anesthesia for several hours.

More efficient throughput
Brain monitoring can have far-reaching benefits for your facility as a whole. Lowering drug doses and accelerating the wake-up process gets patients out of the OR sooner, which allows for quicker and more frequent room turnovers. When patients arrive in PACU at a more advanced stage of emergence, they require less post-op care, which lets nurses perform other tasks and reduces your staffing costs. They also exit the facility sooner, freeing up space in PACU for the next patients who come through.

Depth-of-anesthesia monitoring can help you increase your caseload, but simply equipping your ORs with these monitors isn't going to magically lower your costs and improve your throughput. Maximize the technology's benefits by pairing it with multi-modal PONV prophylaxis, more efficient anesthesia techniques and aggressive PACU management. To maximize brain monitoring's benefits, your anesthesia providers have to use the monitors to titrate drug doses; you have to train your staff to deal with faster room turnovers and patient recovery times; and your surgeons have to be prepared for larger caseloads.

And, of course, awareness prevention
While I believe that improved efficiency is a more compelling reason to use depth-of-anesthesia monitoring than awareness prevention, the problem of intraoperative awareness remains. At the end of the day, we anesthesia providers are in a service industry, and our customers are the surgeons we work with and the patients we care for. I've found that both parties embrace brain monitoring, despite some studies showing it to be no more effective in preventing awareness than traditional vital signs monitoring and end-tidal gases. Patients in particular want to be reassured that the few, well-publicized horror stories aren't going to happen to them. One of the most frequent questions they always ask me is, "How do you know I'm asleep and I'm not going to wake up during surgery?" My standard answer is, "We've been doing anesthesia for more than 150 years, and intraoperative awareness is a rare phenomenon. But I do use this technology, which helps me make sure you're going to stay asleep." (In more than 10 years of using brain monitors in more than 50,000 anesthetics, we've had two documented cases of intraoperative awareness). The peace of mind this affords the patients, the surgeons and myself is a side bonus of the monitors, not the primary reason we use them.

Worth the expense?
While some of the resistance to routine brain monitoring comes from anesthesia providers who are skeptical of its utility in preventing awareness, a more significant barrier to widespread adoption is the cost. The monitors are expensive: about $10,000 for the box/OEM and $20 per probe. That's a big upfront investment that many hospital and ASC managers are hesitant to make without proof that the technology works. I've found that routine depth-of-anesthesia monitoring adds about $5 to $10 to our direct cost per case, but more than pays for itself when you factor in savings on drug and personnel costs and the ability to do more cases.