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Aspect: Can you tell us how you were introduced to the BIS monitor? Dr. Harper: Our anesthesia chief at the time, Paul Grant, was interested in neural monitoring and had tried several instruments to measure depth of sedation. When BIS came along in the mid-90s, we tested several units. We liked them and bought them for every operating room. I like new technology, but I was skeptical about ease of use and accuracy. Since then I’ve become quite comfortable with it and have used it extensively. There are approximately 23 anesthesiologists and 60 nurse anesthetists here, and about 90% use BIS. Ms. DeBusk: The anesthesia department introduced BIS to Harris Methodist. We were in the process of building a critical care tower when the hospital first acquired BIS for the OR, and we decided to install BIS monitors and other high tech monitoring equipment in our critical care units. The anesthesiologists explained how BIS was used to monitor patients in the OR, and we felt that BIS could also be helpful in the post anesthesia recovery phase. In addition, we saw the potential for monitoring critical care patients that require sedation for ventilator management or for procedure management. We now use BIS extensively in all of our critical care areas, including the medical/surgical, trauma, neuro, and cardiovascular ICUs. Aspect: So usage of BIS migrated from the OR to other environments in the hospital? Dr. Harper: That’s correct. Initially some of our neurologists wanted BIS in the neuro-ICU for patients in barbiturate comas. We found our BIS units migrating out of the operating room to the neuro-ICU. As the ICU staff became familiar with the technology, it was used for patients that were pharmacologically paralyzed for mechanical ventilation. Many of our patients are severely ill and medicated with propofol infusions along with their neuromuscular blockade. The nurses now routinely titrate sedation for these patients with the BIS. Aspect: How important is it to have continuity of technology across the hospital, from the OR to the ICUs? Ms. DeBusk: I think it’s very important. Continuity of care helps patients get better faster and go home more quickly. The standards for sedation and anesthesia care apply in any setting where patients receive moderate to deep sedation or anesthetics, and BIS helps us to develop a more comprehensive picture of each patient’s response to sedatives and anesthetics. When BIS use is initiated in surgery and then continued throughout our critical care units, we are better able to ensure that the staff is appropriately trained and equipped to optimize sedation assessment across the continuum, and ultimately keep our patients as comfortable as possible throughout their stay in the hospital. BIS helps ensure greater consistency of care. Aspect: Do you use the BIS monitor on every sedated patient in the ICU? Ms. DeBusk: Yes. We use BIS for every patient that is sedated, and we have established a protocol that designates when to initiate and use BIS monitoring. Specifically, patients that are always monitored with BIS include those that are in a barbiturate coma, on continuous sedation infusions, sedation during mechanical ventilation, or who must be rendered motionless with neuromuscular blockade. BIS-guided sedation titration helps us to better monitor our daily wakeup for the patient and to do a better neurological assessment. BIS has enabled us in many cases to decrease the sedation requirements and shorten the length of time a patient is on a ventilator. This, in turn, can shorten the ICU length of stay.
Aspect: Do you generally find that the BIS range corresponds well with sedation scales that are used in the ICU? Ms. DeBusk: Yes, we do. When BIS is used in conjunction with other pieces of information, like clinical assessment and sedation assessment scales, we are better able to make sound clinical judgments. All nurses have been taught to assess patients using sedation scales, but these scales are somewhat subjective. They also become less useful with deeply sedated patients and are unusable when paralytics are administered. Without the BIS, we’d be making decisions with incomplete information. If we combine the objective data the BIS provides with good clinical and subjective data, then we’re able to provide the best possible care. Aspect: What has BIS allowed you to do that you couldn’t do before? Dr. Harper: BIS has increased my comfort zone, especially in challenging patient populations such as trauma and obstetric cases where the amount of anesthesia is limited by either the condition of the patient or the situation, such as a C-section under general anesthesia. I also do a lot of cases that involve the use of nitrous oxide and remifentanyl for ENT surgery. In those cases you’re skating right on the edge of awareness. I use the BIS to help me determine when it’s necessary to give an extra dose of propofol to prevent awareness. Aspect: Given the relative rarity of awareness, you still see it as a major issue? Dr. Harper: When it occurs, awareness is a severe problem. It causes a fair amount of emotional trauma to patients. Keeping the patient unaware is one of our main missions. Aspect: Why isn’t the solution to awareness or recall simply to err on the side of too much anesthesia rather than too little? Ms. DeBusk: In the ICU, administering too much sedation leads to a number of negative consequences, including increased cost of sedative drugs, increased ICU length of stay, and increased complications. These complications can include anything from increased time on mechanical ventilation to increased rates of ventilator associated pneumonias to more frequent testing when patients don’t wake up when sedation is terminated. Dr. Harper: All anesthetics are harmful if given in overdoses and the correct dose depends on the patient and the patient’s health. Individual anesthetic requirements vary because of genetic differences and environmental differences such as medications, alcohol, caffeine, and degree of anxiety. The correct dose also depends on the operation. Anesthesia is a complex art, and I think it is best to have as much information about the status of my patient as possible. Aspect: Before BIS, how would you account for such individual differences? Dr. Harper: The traditional measures in both the OR and the ICU included heart rate and blood pressure. However, these measures don’t always correlate with the patient’s depth of anesthesia, so when considered alone, they are not always reliable indicators. Aspect: What if you were simultaneously using medication to suppress heart rate and blood pressure? Dr. Harper: In fact, that’s often the case, and it can be more challenging to prevent awareness in a patient taking cardiovascular medications. Reliance upon traditional vital signs as the primary assessment of adequacy of anesthesia is less reliable for these patients. BIS monitoring can provide guidance in this situation by independently measuring anesthetic effect. It is sensitive to anesthetic levels in situations where blood pressure and heart rate responses may be misleading. It also enables the clinician to see the synergistic effect of medications on a patient. The BIS often acts as a catalyst to reassess a patient. If I see a high BIS value in a patient under general anesthesia, I reevaluate the patient’s vital signs, end tidal gas values, drug doses, etc. Ms. DeBusk: Precision is important when giving any kind of anesthetic or sedative. Without a monitoring device that measures a patient’s individual response to sedation drugs, the clinician must rely solely on his or her clinical skills, but runs the risk of a patient being sedated longer than necessary or not being adequately sedated. In the ICU, sedation without some way of monitoring the patient’s ability to be wakeful may mask a neurologic change. There are many complications that can develop if a patient is on continuous sedation and the care provider can’t get an objective measure of sedative effect. Aspect: With what other patient populations do you find BIS to be particularly useful? Dr. Harper: Challenging patient populations, such as trauma patients, geriatric patients or patients with compromised cardiovascular function. I watch the BIS very closely during operations on these patients. There is a great deal of variability in the way patients respond to a given amount of a drug. BIS provides objective data to help us determine appropriate sedation to meet each patient’s needs. Aspect: How have patients and their families reacted to the BIS? Dr. Harper: Patients and families are reassured when we explain that we use the BIS. Many patients have heard about intraoperative awareness, and they are relieved to know that we monitor for it. Ms. DeBusk: We try to explain all of the monitoring devices that families see, whether it’s a heart monitor or BIS, because critical care is a foreign land to most. We don’t want them to be intimidated by the equipment. Many times families focus on those monitors and they want to ensure that their loved one is comfortable. We try to decrease some of their anxiety by explaining what all of the equipment is for, including the BIS. Families are reassured to know that technology is in place to ensure that their loved ones are adequately sedated. Aspect: Are there other hospital environments where BIS might have value? Dr. Harper: I think it will become valuable for conscious sedation patients in the cath lab, endoscopy suite and radiology. It’s not routinely used there yet but I think BIS will become helpful at these locations because non-anesthesia providers are administering potent drugs. |
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Dr.
James Harper is the chief of anesthesia, and Pat DeBusk is a staff nurse
in the medical/surgical intensive care unit (ICU), at Harris Methodist Fort
Worth Hospital where 34 BIS monitors are is use in operating rooms and 50
BIS monitors are in use in critical care units throughout the hospital.
Aspect spoke separately with Dr. Harper and Ms. DeBusk about their clinical
experience with BIS technology and its impact on patient care. They reaffirmed
the value of BIS across the continuum of patient care where anesthesia and
sedation are used. 
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