I've been asked to discuss the anesthetic issues with cortical mapping, and particularly in awake surgery, but what are these challenges? Many of you, I believe, are looking to expand your programs and to do more of these procedures, but good anesthetic management can make or break what you're able to achieve with these procedures. Common goals for neuroanesthesia, obviously, are to protect the brain and to optimize neurophysiologic intraoperative hemodynamics, etc., but we also need to provide adequate analgesia, sedation, and amnesia. I'd like to talk a little bit about how the choice of our drugs can influence the brain conditions just very briefly. Remember, the cerebral vasodilators, potent inhalational agents, can cause a lot of cerebral vasodilation, nitric oxide mediated, as well as some of the blood pressure vasodilators. Typically, the IV anesthetics are more prone to cerebral vasoconstriction and can help avoid some of the brain swelling that we see, and of course, some of our vasopressors don't cross the blood-brain barrier. I can go up for the individual who wanted to take that picture again. All right, but the goals of neuroanesthesia become a little more challenging when you have to deal with surgical resection in eloquent areas and when you require electrocorticography or brain mapping. There are significant constraints, the anesthetic effects that Dr. Shills referred to on electrophysiologic testing and, of course, the challenges of wakefulness and cooperation in the patient. We try to break up, maybe for purposes of discussing these issues, to the surgical stages. We have the portion of surgical exposure, which can be very stimulating and painful for an awake patient, obviously, the intraoperative testing and functional mapping, continued resection of the target lesion, and then the closure. Under general anesthesia, again, as we discussed in the prior talk, the anesthetics can affect the SSCP. When you're localizing central solicus, for example, the general anesthetics will decrease the amplitude and increase latencies. The motor vote potentials are very sensitive. With motor stimulation, we have to avoid muscle relaxation and increase the stimulation amplitude. We want to not dampen the EEG because, again, we're looking for after discharges. We need lower concentrations of the inhalational agents. Often we consider a total intravenous anesthesia technique or some combination thereof to give good electrophysiologic monitoring. We have to avoid boluses or sudden changes, which can influence the monitoring. Over time, you can see a decrease in amplitudes and effects on latency. Blood pressure, temperature can affect it. Certainly, if you shrink the brain with mannitol, the brain comes further away from the scalp and can give changes there. But under general anesthesia, remember, there are hemodynamic influences. You are with a lighter anesthesia. You have the risk of movement, recall in the patient, and of course, you don't have a standard of awake testing, so you can have more false positives or negatives. But particularly for sensory motor or language stimulation mapping to be performed, the patient must be awake and cooperative, and that's one of the challenges. Just to describe what we're doing with an awake craniotomy, the critical portions are the pre-op evaluation, preparation. I've been known to repeat over and over that it doesn't matter until it matters. We'll talk a little bit about techniques, the intraoperative concerns, and of course, how to manage or address some critical events. The neurosurgical aspect of the pre-op evaluation, as an anesthesiologist, it's important for me to really have a sense of where the lesion is located, what are the ICP risks, what are the bleeding risks. Those are discussions I would have preoperatively with my surgeon. We have to get a sense of what the deficits are. You need a reliable baseline to be able to map this, particularly if we're now going to sedate the patient. And for sensory motor or language, you really only can have a mild deficit. Typically, some patients present with a more severe deficit, but with steroids and over time there's some improvement and they can present then for a wake craniotomy. Why do we care about some of these, even more so, some of the typical preoperative issues? Well, for example, conduction. These patients can be prone to bradycardia with the stimulation. If you have a patient who's had a cold and is coughing, that can be very detrimental intraoperatively. And of course, the priority is the airway, obesity and difficult airway anatomy can be very challenging with obstruction and hypercarbia, et cetera. It's very important to make sure that the patients are on their antihypertensives and anticonvulsants because of the increased risk for seizure and for sympathetic stimulation. And preoperatively is the time to get a sense of whether some of these patients are predisposed to a rapid drug metabolism, obviously, when they're anticonvulsants, the P450 is accelerated and some of these patients really need more medication. And of course, the elderly or diabetics may need less, so you have to get a sense of where you're going to fall because it really is titrate to effect. Here's an example of a patient who is morbidly obese and prone to obstruction. The lady on the right has a very anterior airway and while less likely to obstruct would certainly be a challenge in an acute situation to try and get the breathing tube in and secure the airway. Epilepsy history, I alluded to, it's good to know what their seizure or what their deficit is like postictally, and we talked about existing deficits. Psychological, I can't really under emphasize how important that is, knowing whether this patient is anxiety prone, whether their pain tolerance is high or low, and really how motivated they are to get this to succeed. So patient collaboration is really important, letting them know what's going to happen, how they are going to still be in control at many moments, knowing what the airway is going to present to us. Anti-nausea medication, boy, you really do not want to have a patient throwing up when they're in pins and awake. It could really ruin what is to come. Make sure the anticonvulsants are on board, and then have all that equipment we need, the ice saline, special airway rescue techniques, and make sure that neuromonitoring personnel have been notified about the scheduled surgery. We have many options for airway rescue. I'm just throwing this up so that you kind of know a little bit of what's, there's a lot of video fluoroscopy, having a fiber optic available immediately if you think that it potentially would be necessary, and then there are other techniques like the intubating LMA. So let's talk a little bit about techniques. Obviously the goals that are common are wake and cooperative during testing. We need to manage a neurophysiologic milieu. We have to mitigate pain and anxiety, particularly during those stages that we discussed of exposure, resection, and closure. Under local, regardless of how you proceed, you really need good local anesthesia. Some people do it exclusively. Conscious sedation can be varied to having them more asleep at the challenging moments. They can really end up with a post-traumatic stress disorder type of picture if they've really had a very bad experience. And then there are degrees of being asleep. Some centers prefer a general anesthetic and then emerging into the awake stage, and we'll talk a little bit about that. So what we use for local at our center is a combination of bupivacaine, which is a little longer lasting, and 1% lidocaine with the epi. When you add the epinephrine, you can extend your toxic doses. Remember, local anesthetics do have toxic potential cardiac-wise. You can lower your seizure threshold with high doses, and you have to be cautious of the epinephrine because you can get some absorption. As a reminder, people forget, they think that they've reached this maximum dose, but over time during the surgical procedure, these patients who metabolize drugs quickly will also metabolize their lidocaine very quickly and will often need supplementation. So we localize pin sites, a generous field block over the incision, scalp blocks. Just as a reminder, the dura, everybody knows, has sensation and can be very painful, and particularly in this area where patients start complaining about some pain to their eye or their ear, and adding some infiltrate around the middle meningeal artery there can help alleviate that. The temporalis muscle has a very robust innervation, and if you can block this a little bit, it can decrease some of the sympathetic stimulus, but again, I caution, and you can see, hopefully in some of the movies, how much the temporalis muscle can influence. When they're talking, you can see the muscle contracting. So we use multiple drugs for conscious sedation. Typically it's some combination, many centers use different things, but some combination of narcotic fentanyl, midazolam, just a little bit can help block your risk for seizures, but it can influence your EEG, cause some disinhibition. I use propofol as a background. Some centers would like to use this at a higher sedative dose. Remember you have more airway depression with this drug, and I found that, especially in young people, you can get some disinhibition unless you add some of the other medications, and then you have this more abrupt, startle awakening. Remifentanil is IV opiate that is very short-acting when you turn it off. It's metabolized by plasma esterases in about six minutes. And dexmedetomidine is an alpha-2 agonist. Typically, it can provide analgesia, it can provide anxiolysis, and gives you a cooperative sedation where you can test somebody, and it sort of mimics sleep, and they can recover from that and respond to testing very easily. You have to remember that all of this is a recipe that has to be varied according to patient. You have to have discussion, cooperation with your surgeon and the patient in terms of timing and arousal. If people want a little bit more information, we introduced dexmedetomidine for neurological surgery in 2005, and you can see a lot of the properties that make it ideal for neurosurgical case management. It has less effect on somatosensory evoked potentials, and there is a little bit of controversy as to the EEG. Typically, alpha-2 agonists are activating and lower your seizure threshold. However, we've seen some asleep EEG patterns. Some centers, as I said, prefer general anesthesia for the asleep portion. There are many techniques using a laryngeal mask airway and removing it. You have risk for aspiration in those instances and vocal cord laryngospasm. There was a recent publication here at University of Penn where they're applying nasal trumpets. This is an awake and lightly sedated patient, and they felt that they can provide positive pressure ventilation, avoid the hypercarbia, et cetera. I just wanted to point out that it is concerning to me. Some of these are typical. Remember, Dr. Golby alluded to the fact that you can have a lot of issues with anesthesia that can interfere with success, 20 to 30 percent, I think she mentioned. But this is a little high for brain swelling, I think, and that's one thing you want to avoid. So regardless of your technique, you want a smooth emergence. You want to recover from your consciousness without coughing or straining, and you want to avoid arterial hypertension. It's a little harder with general anesthesia. There are pros for general anesthesia, obviously the comfort aspect and a little more control. The cons are the airway challenges, the issue of timing, delays in emergence, and unpredictability of such. But I think whatever you do that you do frequently often works well. Interoperatively, we need to manage the airway, whether it's general anesthesia or sedation, the hemodynamics, the brain conditions, and really the key is to just pay attention to how the patient feels and their sense of well-being and participation, and of course, I always pay attention to the surgeon's sense of well-being. So positioning is very important. Because it's the start and it sets the tone for how things are going to succeed. Comfort for neck and body, the airway access, and good venous return. So large craniotomy necessary for the probable cortical stem sites and you're a little more predisposed to swelling. You need a visual line for object naming or testing. At our center, we use rigid fixation. It gives you better control and particularly if the patient becomes a little disinhibited and wants to go home. For those reasons, we also secure the patient to the OR table until we have a chance to either influence them with magic drugs or reassure them. And you know what? If you've got to go, it's really hard to stay still and participate. So foleys are the norm for us. Here we have a picture of the positioning this patient's asleep and this is again the head pinning, etc. And then just a visualization of putting some arm straps here secure. We often tape across the body if we can and have lateral positioners. Because it's not an easy anesthetic to have or an easy procedure to lie for many hours on your side and comfort and padding and everything is very important. I can't emphasize how much it's important and how small changes and how you position the head can influence your venous drainage and your risk for obstruction and airway issues. Here again now, I'm sorry. Just to show again, having the patient asleep in comfort area here. And then checking to see how the patient is, waking them up, making sure they're comfortable and then testing a little bit to kind of prime them for what's to come. For the benefit of time, I'm just going to point out again, you need to have a clear line of sight. And then now we're prepping the patient. Also critical intraoperative events, loss of the airway, nausea, vomiting, hemodynamics, over sedation, I'm sorry, somehow this has changed my, pain and discomfort obviously, stress, restlessness, the risk for seizure, air embolus and ICP, swelling issues, most of all control the blood pressure. And this is what we want to try and avoid. I want to show you that buckling and straining, how important it is. Just a second now, cough for me. And cough one more time. Okay now, as big a cough as you can. Okay, now I want you to sort of bear down like you're going to the bathroom, you know where you hold your breath and you sort of bear down. Hold your breath and then bear down, yeah, hold it, hold it, hold it, hold it, hold it. So you can see how high your ICP can go just with buckling and straining. I'm going to skip over venous air embolus. Suffice it to say that they can present with coughing and confusion and blood pressure issues and typically giving them 100% oxygen in the typical maneuvers even under general. Pressure discharge stimulation, you can see. And this shows again, you can add some saline. Got a nice one here. And here you have propagation of... Still going. It's propagating the P8. This is where you have to pay attention and be very clear that they are at risk for seizure at this moment. Motor testing. Nothing there, huh? Yeah, she's having twitching in her chin. Yeah, it's pulling like a little tightness in the mouth. In the mouth. There you go. What happened, Mary? She hurt her lower jaw. Tell them, Jenna, what you felt. A little tightness in the mouth, sort of like... Okay, Jenna, tell me if it happens again, okay? Okay. So, again, I apologize for the time issues. No. It's important while they're operating to be looking, to be constantly testing. Yeah, and looking in the lips. Look at your toes. Feel your fingers. Good job. And testing for motor. With the wake speech testing, I'd like to show this primarily. This is with Dr. Byrne. All right, let's try here. Okay, let's start moving back. No A.D. What is this? Okay, give me another positive. Very clear speech arrest at A, okay. No A.D. And that's the resective cavity there. I wanted to show, again, you can have different types of speech. This is a rapid firing speech. Toothbrush. Helicopter. Room. Octopus. Take another look at it. What do you think it is? Open your eyes. Are your eyes open? When listening? Yeah, I know you're listening, but can you see? Yes. Can I see your eyes open real wide? Yes. There you go. What do you think this is a picture of? That's a great pen. So, importantly, again, in summary, it's important to prepare. It's a team effort. We need to watch the surgery, anticipate, and, of course, everything happens when you walk out of the room and leave the resident alone. And, finally, the lessons that I've learned. You can reward the patient with ice chips. Just don't tell anybody because if they aspirate, you look really bad. It's important to bond with the patient and really make them feel like, you know, you're cheering them on. You know it's difficult for them, but if they can just hang in there with you a little bit longer, everything will work out. And, as always, laughter and music helps in the operating room. Thank you again very much. I appreciate your attention. applause

awake surgeries

neuroanesthesia

cortical mapping

anesthetic management

brain protection

patient collaboration