Hello and welcome to today's webcast, Neuromonitoring at the Bedside. My name is Swarna Rajagopalan. I'm a neurointensivist and associate professor of neurology at Cooper University Hospital and Cooper Neurological Institute in Camden, New Jersey. I'll be moderating today's webcast as well as speaking. A recording of this webcast will be available in five to seven business days. Log on to mySECM.org, navigate into the My Learning tab and click on the Neuromonitoring at the Bedside course. Click on the access button to access the recording. Thanks for joining us. A few housekeeping things before we get started. There will be a Q&A at the end of the presentation. To submit questions throughout the presentation, type into the questions box on the right located on your control panel. Please note the disclaimer stating that the content to follow is only for education. And for speakers, I'd like to first introduce you to Golda Boahene-Norte. She's a clinical nurse at Icahn School of Medicine at Mount Sinai and Department of Neurosurgery in New York. She has over a decade of bedside neurocritical care experience and she's going to share some of her extensive knowledge with us. And take it away, Golda. All right. Good afternoon, everyone. My name is Golda Boahene-Norte, and I am very honored to be able to share with you my thoughts and feelings about neuromonitoring at the bedside, a topic which is very near and dear to my heart. So my objectives for today are to be able to describe the significance of neuromonitoring in brain injured patients. I hope you'll be able to acquire working knowledge of the different types of monitoring modalities available and also be able to identify external ventricular drains and ventricular drains that are used in brain injured patients. To provide context around the topic of neuromonitoring, I feel it's best to do it by way of a case study. So we have a 44-year-old woman who presented to the ED with a history of asthma and with the worst headache of her life. She also had some photophobia, nausea, however, no vomiting. CT, CTA was done, which showed some arachnoid hemorrhage, some hydrocephalus, and a right ophthalmic aneurysm. Her blood pressure systolic in the ED was in the 150 to 160s. She was started on an antihypertensive to try to get her systolic blood pressure to less than 140 to help prevent re-bleeding. She was admitted to a neuro ICU very shortly after that, where an EVD was placed at the bedside, and she was ordered for neurologic assessments and pupillometer checks every hour. So here is the subarachnoid hemorrhage on CAT scan, and this is an infographic of the EVD in place. Continuing with the case study, the next day around 9 o'clock, she became very somnolent, and on ICP check, her ICPs were hanging in the 23 to 25 range. There was some troubleshooting done. However, it did not come down. It was also noted that her MPI from the pupillometer checks had decreased from 3.1 to 1.5. So she got some treatments, which included hyperventilation and administration of hypertonic saline, 23.4%, and this helped to bring that ICP down to the 13 to 15 range. So that brings us to our main topic for today. What is neuromonitoring? So neuromonitoring is essentially an application of one or more modalities, which are used as tools to support clinical decision making. It alerts clinicians to changes that need to be acted on to prevent further injury, and some modalities can even assist with the treatment of certain issues, such as giving medications or sampling. So this is what neuromonitoring looks like, right? It goes from when it comes to the care of brain injured patients, the more information that we can obtain, the better it is in order to help manage these patients. There are a myriad of neuromonitoring parameters that can be explored to yield worthwhile information. Anything from non-invasive as a neurological assessment down to being very invasive as the placement of death electrodes, all of these monitors give us information, which we can use to help patients so they don't decline further. The neuroassessment, which I want to talk a bit about, is actually a very important tool. It's the most basic and important assessment tool. Typically, when it's done consistently and frequently, it can alert us to changes which require intervention. It needs to be done very diligently and in the same manner each time, so we can truly appreciate any subtle changes that happen. For our particular patient from the case study, she did get quite a few neuromonitoring tools. She was ordered for the neuroassessment, she was ordered for pupillometer checks, and she had an EVD in place. All of these gave us information that we could work with to try to help prevent any further decline. For the sake of time, I'm going to focus mostly on the extraventricular drains, EVDs for short. The EVD is a closed sterile system, which is inserted into the ventricle to allow for CSF drainage and to monitor intracranial pressures. It is the gold standard in intracranial pressure monitoring and is one of the most commonly performed neurosurgical procedures at the bedside. The catheter which is used is typically antibiotic impregnated in order to help prevent infections. EVDs are typically indicated for acute hydrocephalus and increased ICP in subarachnoid hemorrhage patients, but it can also be used in intracerebral hemorrhage patients. The device, when it comes out of its packaging, is really only able to drain CSF. However, you can attach a transducer to this part of the EVD, and once you attach a transducer, you can be able to now obtain intracranial pressures as well. The EVD performs these two functions independently. In order to drain CSF, a measurement for ICP needs to be turned off and vice versa. In order to obtain an ICP, drainage needs to be turned off. Some additional benefits of the EVD are that it can be used for sampling of CSF and also it can be used to administer medications intrathecally. It is worth mentioning that the American Association of Neuroscience Nurses is a really important body which sets recommendations and guidelines for the nursing care of patients undergoing intracranial pressure monitoring. Typically, most nursing policies and procedures and protocols are typically derived from their guidelines. Also, it's important to know that any nursing policy which addresses the care of the patient with a drain needs to focus on a lot of things, including setup, insertion, maintenance, documentation, transportation, sampling. All of those elements need to be included in a policy to ensure that patients that need this are being taken care of to the utmost best. So we're going to dive right into what the EVD looks like. Here we have a front view of what an EVD looks like, and there are several different manufacturers in the market, but typically all EVDs will have the same characteristics. On the front of this particular device, you have your pressure settings, and you can have settings in either centimeters of water or millimeters of mercury, and there's also this part over here, which I want to point out. This is where we can attach a transducer so that we can have the EVD also measure intracranial pressures. Most institutions, you typically tend to set their EVDs to a level of centimeters of water, and typically what that means is if a patient has an EVD and they're set to say 10 centimeters of water, what it means is when their ICP reaches 10, there's going to be drainage of CSF, so that's the way to interpret that. For the side view, the side view mostly shows the drainage chambers. There's a drainage chamber, which is this buritual-looking device here, and then there's the bag, which is further down. There is a stopcock in the middle, which helps control drainage from the drainage chamber into the bag. Below that is the connection that will go to the catheter that's actually coming out of the patient's ventricles. Most drainage chambers can hold up to about 75 mLs of CSF, and the bags typically can hold up to about 700 mLs of CSF. It is important to know that once this bag fills up, it needs to be changed so that another bag can be used. On the back of the EVD, you have your securement straps, so this particular device actually has three different securement straps. There are straps that hold the drainage setup onto the pole itself, and then there's a string coming off the device, which you can hang on the pole, so you have three points of securement. This is all important to make sure that they're always in place to prevent any inadvertent removal of the device from the pole. So, as I had mentioned before, in order to get intracranial pressures, you need to attach a stopcock. So, this is our stopcock over here, and the stopcock needs to be prepped sterilely, right, because we definitely want to make sure that we're not introducing the patient to any sort of infection. It is attached to this setup. The stopcock, which is over here, is attached to the setup on the opposite side from where the drainage bag and the drainage chambers are. You have to ensure that the stopcock that's on the actual device is turned towards where the transducer is going to be placed, right, to make sure that there is no inadvertent leakage of CSF, and when you attach the transducer, all you're doing is just sort of placing the transducer into the port, and you're screwing it onto the transducer, onto the stopcock, sorry, and you have to make sure that you're tightening everything, right, because again, we want to make sure that we don't prevent any accidental removal of the EVD or the transducer. In order to get the EVD to yield accurate data, it needs to be leveled and re-zeroed. It needs to be leveled and zeroed for calibration purposes. In order to level, we need to ensure that the patient's head of bed is at least 30 degrees or greater, and what you're going to do is you're going to stretch out the string over here and bring it towards the tragus of the patient and make sure that the bubble on the level stays in the middle. That's how you know you're really leveled. It should be noted that some devices use lasers, and so if you're using a device with a laser, you need to make sure that the laser is pointing to the tragus of the patient's ear, and also you're going to watch for the bubble in the middle for the level. After leveling, you're going to remove the cap covering the stopcock, and then you're going to turn your transducer stopcock away from the transducer so you can have the transducer open to atmosphere and be able to zero it. You're going to go to your monitor that's connected to the EVD setup, and you're going to use the menu to be able to zero the EVD and get it to work properly. Once it's been leveled and zeroed, you know calibration has happened, so after that, any time you check for an ICP, you're going to know that you have the right ICP for the patient. All right, so ICP will be measured and ordered by institutional policy, and the frequency for doing so will depend on wherever it is that you are. In order to get an ICP reading, we need to clump the system, right? So clumping the system means returning the stopcock away from drainage. Once we clump the system, it stops CSF flow and opens up the transducer so that it converts the flow of the CSF into waveforms, and the ICP can be derived from that. In order to get an ICP reading, once you clump it, you're going to wait for about five to seven seconds and watch the numbers on your monitor. Once the number stays constant for about five to seven seconds, that's what your true ICP will be, and that's the ICP to document for your patient. The left side, the right side of this slide shows the different ICP waveforms, right? So this one is what a typical normal ICP waveform looks like. There are three strokes, right? There's P1, which shows your percussion wave. It represents arterial pulsation. There's P2, which is your tidal wave. It represents intracranial compliance, and there's P3, your dicrotic wave, which represents venous pulsation. In a normal ICP waveform, P1 should always have the highest upstroke. P2 is between, and P3 should show the lowest upstroke. Whenever you have P2 higher than P1, as in this illustration, it shows that there is increased intracranial hypertension, and this shows there's a sign of non-compliance in the brain. It is worth noting that if a patient has had a hemicraniectomy performed, you're not going to be able to see these crisp waveforms or these crisp strokes, but whatever ICP number you're deriving when you clump it is still accurate and should be relied on for treatment purposes. The other thing that EVD is able to do is to drain CSF, right? Depending, again, on institutional policy, you're going to have CSF collect in the drainage chamber, and every hour, every two hours, whatever the order is, you're going to go in and observe the CSF that's in the drainage chamber. You're going to measure the amount of it. You're going to investigate the color, because these are all data that's going to give you information about what's going on with the patient. Once you're done recording that information, you're going to have the CSF in the drainage chamber drain into the drainage bag, and then you're going to clump it again using the stopcock so that it collects for the next time you're going to check your CSF drainage. So, given that the insertion of an EVD is such an invasive procedure, infection is the number one issue when it comes to doing these procedures. It sets up the right conditions for an infection, so strict aseptic technique is always warranted whenever there's manipulation of the device, whether it's an insertion, it's sampling, it's removal, it's dressing change, or any such thing. There are lots of studies which have found that institutions that utilize bundles actually do well in terms of reducing their ventriculitis rates, so it's really important to make sure that we always have checklists, and the checklist ensures that anybody who's in touch with the EVD is performing their procedures properly and making sure that they're not potentially exposing the patient to any sort of infection. So, with all that said, we're going to look at some important considerations when it comes to EVDs. So, the most important thing is, once the EVD catheter has been placed at the bedside by a medical provider, the one thing you can do as a nurse or anybody else is to make sure that the EVD is secure, right? A simple thing to do is just to secure the tubing coming from the ventricles behind the patient's ear. You cover it up with a clear dressing, and then you can trace it along the patient's shoulder. You cover it up with a clear dressing there as well. This is to make sure that you have two points of securement so that it doesn't tug and inadvertently come out accidentally. Another thing to also make sure, which I spoke about earlier, is to make sure that the EVD is always secured on the pole, again, to prevent it from accidentally falling off the pole, which can lead to the catheter actually coming out of the ventricle. The head-off-bed angle is really important. In order to facilitate CSF drainage, the head-off-bed needs to be at 30 degrees or greater, and the patient's head also needs to be midline. So, if you're having any issues when it comes to drainage, you know, those are some of the easiest things you can do is just checking to make sure your head-off-bed is okay and the patient's head is midline. Another important consideration to do is, just like any sort of pressure monitor, calibration always needs to happen, right? So, typically, at the beginning of any shift, you need to make sure that your EVD is leveled and it's zeroed. Also, anytime the head-off-bed angle is changed or if the patient moves in bed, you need to always go back and re-level and re-zero, because in order to really truly take advantage of whatever ICP number you're getting, it needs to be done under the right conditions. You're also going to clamp the EVD before any activity that causes stimulation, because this can lead to over-drainage of CSF. So, anything that causes stimulation, like transporting the patient, suctioning the patient, turning the patient, any of those things can lead to stimulation, and because we don't want over-drainage of CSF, you have to make sure you clamp it before you do any of those things. And lastly, education of the patient and family is also very important, right? It can be daunting to have a catheter coming out of a patient's head, and it's even more important to make sure we're educating them, because this is such a high risk for infection. We want to make sure that patients aren't touching the dressing site, because that could expose them to an infection. So, a lot of education needs to happen when it comes to patients with EVD inserted. We're going to look at some troubleshooting tips. The first one to look at, you know, if your patient has an ICP, which is greater than what the set threshold is, anywhere between 20 to 22, you can do a few troubleshoot, easy troubleshooting tips, I should say, right? What I was saying before, you always have to level, you always have to zero, check your head of bed, keep head midline, and sometimes this can fix the issue, right? However, if you do all these things and your patient's ICP is still greater than what is recommended for at least five to ten minutes, this indicates an ICP crisis, and this requires treatment, treatments such as hyperventilation, administration of hypertonic saline, you know, sometimes if none of those things are working, the patient might need to go to the operating room for a hemicraniectomy to try to resolve that ICP crisis. Sometimes, you know, you go to check your ICP and you notice that you're getting negative numbers, right? Again, you're going to do the first troubleshooting methods, always level, always zero, keep your head off bed, 30 degrees or greater, keep the head midline, right? Another thing you can do is to check your cable connection from the transducer to the monitor. If all else fails, you've performed all these interventions and the patient is still getting negative ICPs, it will be time to escalate that and talk to the medical provider because we may need to eventually change that transducer setup, and when it comes to changing the transducer setup, again, it needs to be done very sterilely because we don't want to expose the patient to any sort of infections. Sometimes, you go to check your CSF and notice that there's no drainage in your drainage chamber. It could mean several different things, but a very easy thing to do is to completely remove the setup from the pole, and you're going to lower the setup below the level of the patient's head, and since it drains by gravity, you're going to observe the drainage chamber and see if there are any drips at all. If you don't notice any drip, it could mean that there's some obstruction further along in the EVD tubing, and that is going to require an intervention by the medical provider. And also, depending on your institution, you're going to set the role for what is considered excessive CSF drainage. However, if you've had excessive CSF drainage for two hours, it's also a cause of concern because, again, we want to prevent over-drainage, so this is a conversation to be had with the medical providers to try to figure out what needs to be done. And finally, you need to pay close attention to the CSF drainage, right? Any CSF that is bright red indicates an acute bleed, and that needs to be tended to right away, or if you have CSF that's cloudy, it could be the sign of an infection. So these are all things that need to be escalated and taken care of. So that's pretty much a wrap-up on EBDs, you know, plumping ICPs, draining CSF, and I'm gonna finish this with the conclusion of our case study from the beginning. So this patient went on to have a few more ICP crisis. She became stable once her ICPs had all been normal, her pupillometer readings, her neuro exam were all totally fine. She had a repeat CAT scan done, which showed a resolution of her hydrocephalus. So the decision was made to remove the EBD. She was weaned gradually, and after a day, she was able to have the EBD removed, and she was transferred out of the ICU and ended up doing really well. So these are my references, and I am gonna turn it over back to Swarna so she can get into a bit more detail about intracranial pressure monitoring. Thank you. Thank you so much, Golda, for a really, really in-depth discussion. So I'm gonna change gears a little bit and talk about intracranial pressure monitoring. To many, the brain is kind of a black box. For instance, you know, patients are having a STEMI, we use troponins and EPGs. Some, you know, we're treating someone with ARDS, we are looking at their arterial blood gases and pulse ox and chest X-rays. In patients with acute brain injury, the way we do, when we monitor them is typically through a neuromonitoring. So what does that mean? We'll talk a little bit about why we neuromonitor people, how, do's and don'ts, and, you know, tips and tricks. Okay, so why do we monitor people? After acute brain injury, the injury, unfortunately, doesn't stop right there. It leads to a cascade of secondary brain injury. This includes, you know, seizures, raced ICP, cortical spreading depolarizations, edema, impaired cerebrovascular reactivity, and microvascular dysfunction. So there's a lot of secondary brain injury that compounds on the primary brain injury that we can focus on and limit with neuromonitoring. And the goal eventually is to improve patient outcomes and limit neuronal death. So let's talk a little bit about the basics. So the Monroe-Kelly Doctrine dictates that the skull is a fixed space. And, you know, if you increase one component, it must be offset by a decrease in another. So this is the intracranial cerebral compliance curve. You can see that, you know, in the early portions, small changes in intracranial volume result in small changes in intracranial pressure, and the brain is compensating for it pretty well. But once you reach an inflection point, any small change in intracranial volume will result in an exponential increase in your intracranial pressure. This can result in tissue shift and herniation. So it would be really useful to know when patients are progressing through this. So how do we monitor ICP? The two most common ways we measure them are through an external ventricular drain, an intraventricular approach, and an intraparenchymal approach, putting a monitor in the parenchyma of the brain. There are also other types of monitors, such as subdural and epidural, with varying accuracy. So these are sort of the two more common approaches. This is an example of an EVD in a patient. An extraventricular drain, it's being tunneled under the skin and then connected to an external chamber. There's two ways it can actually be attached. It can be tunneled under the skin after it's inserted, or it can be attached to a bolt, which is this sort of metal thing here, and then attached to the drainage bag system. Usually EVDs are made of silicone. They most commonly are antibiotic impregnated, and they're coated with thrombus-reducing polymers. I wanted to point out here that the EVDs have drainage holes not only at the end, but also towards the end. So even if the EVD is sort of, it looks like the tip is not in the perfect position, you still may be draining CSF because of these other holes. These are examples of EVDs in patients. So you can see here the coronalis or sagittal view. You can see that the EVD tip terminates in the right frontal horn of the labral ventricle, and you can see the axial slices in the same patient here. And this window, once you switch to the bone window, so EVDs can either be radiopaque or translucent, or a combo, but switching to the bone window, you might be able to see the EVD holes a little bit better. So this is a nice example of that, not only looking at the tip, but also at the holes. Another, changing gears a little bit, intraparenchymal monitors. So intraparenchymal monitors, also like an EVD, require drilling a hole in the skull and then placement into the parenchyma of the brain. Using a bolt at the exit point, you know, there's different bolt types. There's single-lumen bolt, and there's also multi-lumen bolts. So if you're monitoring different parameters within the brain and placing different catheters for those, then you might need to use a multi-lumen bolt. These are examples of intraparenchymal monitors terminating within the parenchyma of the brain. This is a nice sagittal CT of the same thing. So as with any procedure, you always want to weigh the risks and benefits. And, you know, the benefits have to outweigh the risks. The obvious risks with coagulopathy and anticoagulant medications are, you know, increased risk of hemorrhage. So who do we monitor? So there's some guidance on this. In severe traumatic brain injury patients, the Brain Trauma Foundation, the Brain Trauma Foundation provides some guidelines. So in someone with traumatic brain injury and an abnormal CT and a Glasgow coma score of under 9, so 3 to 8, after resuscitation, we should do ICP monitoring in them. So what if the CT is normal? So in normal CT patients with acute TBI, if they meet two out of the three criteria, hypotension, systolic, blood pressure under 90 millimeters of mercury, posturing, or age greater than 40, if they meet two out of these three criteria with a normal CT and normal CT, they might still qualify for ICP monitoring. In spontaneous ICH with intraventricular hemorrhage and hydrocephalus, ICP monitoring is indicated and CSF drainage. And what about in focal lesions, like a large ischemic stroke? So EVDs and intraparenchymal monitors can be falsely reassuring because intracranial pressure is compartmentalized. So even though there's significant swelling in one compartment, it may actually be falsely reassuring. The ICPs may not go up. So, you know, caution in focal lesions. And in acute aneurysmal subarachnoid hemorrhage with hydrocephalus that's symptomatic, CSF drainage and ICP monitoring is recommended. A couple of cases. So this is cases that, you know, need neuromonitoring. 45-year-old woman with a past medical history of hypertension is evaluated in the emergency room with worst headache of life. She is hypertensive. Her GCS is 15. She has no deficits, but then she gets more drowsy. Her GCS decreases to 11. Hypertonic saline is administered. So what's going on? Here, you look at the CT. You see the obvious hyperdensities, which are blood. And then I like to call it the evil pumpkin sign. I'm sure people have different names for it. You know, eyes, nose, and green pumpkin. But the ventricles are dilated. And as long as the obstruction is distal to the lateral ventricles, one of the earliest or most sensitive signs of hydrocephalus is actually dilation of the temporal horn. So I always look out for that. But here's an example of a patient with acute hydrocephalus. This patient in this case with aneurysmal subarachnoid hemorrhage, remember we talked about that, that when it's symptomatic, they need CSF drainage. So EBD would be the right choice for it, for neuromonitoring in this patient. This patient, 62-year-old man, has intracerebral hemorrhage and intraventricular hemorrhage. GCS score is eight. He's intubated. He's hypertensive. EBD is placed. No significant drainage, unfortunately. On head CT, EBD is confirmed to be in the right frontal horn. CT angiogram's negative. So what do we see here? We see large intracerebral hemorrhage, intraventricular hemorrhage. The ventricles are dilated, resulting in hydrocephalus. So this patient needs emergent CSF drainage. So that's sort of, you know, when we think about EBD versus intraparenchymal monitors, you also have to assess, like, what the patient needs, right? If they need CSF drainage, then EBD would be the right choice there. And then, you know, if you're just looking for continuous ICP monitoring, an intraparenchymal monitor might be preferable. There is a lower symptomatic hemorrhage risk and infection risk with the intraparenchymal monitor. So you have to weigh the risks and benefits and assess what the patient needs. So in this case, we are looking for CSF drainage. So an EBD would be the right type of ICP monitor in this case. Oh, and in addition, I should mention, EBD also offers an opportunity to provide treatment. So, for example, in subarachnoid hemorrhage, when you would like to deliver intrathecal vasodilators or, you know, calcium channel blockers, an EBD offers the opportunity to do that. In ICH, if you would like to deliver alteplase interventricularly, the EBD offers an opportunity to do that. This is an example of a penetrating trauma, a gunshot wound to the head. You can see some bullet fragments here and the trajectory of injury here. So 21-year-old man, gunshot trauma. GCS scores three. His ventricles are collapsed. He's got severe TBI. So what type of monitor could you use here? So the ventricles are collapsed. It probably is pretty challenging to place an EBD. There's no obvious reason this man needs CSF drainage. So an intraparenchymal monitor might be reasonable in this case. Complications with ICP monitors. They can be malpositioned. You can get tract hemorrhage. Some studies quote 5% to 10% of hemorrhage risk. The symptomatic hemorrhage risk is actually much lower than that. Any monitors can come with a risk of increased infection. The longer you leave them in, the higher the risk of infection. Obstruction, particularly with EBDs. And intraparenchymal monitors are prone to drift. So remember Golda went over zeroing and calibrating EBDs. So when intraparenchymal monitors are inserted, they're calibrated on insertion, but not after that. But what ends up happening with intraparenchymal monitors is over time, over several days, it starts to drift. And there's no option to re-zero it or recalibrate it at that point. So that's one of the limitations of intraparenchymal monitors. So let's look at what an ICP waveform looks like normally. So in healthy brain, there's typically three peaks. Sorry, that's actually unhealthy. Healthy brain, there's three peaks. So it helps to know how these waveforms are created for you to know what these peaks mean. So the ICP waveform is actually created by intracranial vessel pulsations and choroid plexus pulsations. So you can imagine if it's from blood flow in the head, then it should have some relationship to their arterial line. So let's look at the A-line waveform. So P1 is actually your systolic peak. And your P3 is your dicrotic notch that you see on your arterial line, which signifies aortic valve closure. And P2 is a compliant or tidal wave. So this now depends on what the bounce back is in the medium, which is your interstitium of the brain. So if the brain is noncompliant, then you get a big bounce back, which is your P2. I like to always tell trainees that if you're looking at an ICP waveform and it's giving you the middle finger, it in general is not a good sign. It probably means they have poor brain compliance. One thing to point out is people monitor intracranial pressure using both millimeters mercury and sometimes centimeters water. So this is the conversion formula if you're using one to another. So this is, again, the cerebral compliance curve. But this is the trajectory of someone who is developing increasingly worse intracranial hypertension. So you see somewhat of a normal waveform here, right? P2 is less than P1. And then as you progress, you see that P2 is starting to go higher and higher. And now we've started to hit a little bit of the inflection point, where small changes in the brain started to hit a little bit of the inflection point, where small changes in intracranial volume are leading to larger changes in ICP. You see the P2 picking up here. It's similar to the P1 amplitude. And then it overtakes the P1 amplitude here and here, where it really signifies impending herniation. The Brain Trauma Foundation advocates for treating ICPs greater than 22. So across a lot of disease states, the ICP treatment thresholds are varied between 20 and 25 millimeters of mercury. So 22 is sort of the recommended treatment threshold in TBI patients. So this is a great example of the ICP waveform and kind of signifies why waveform morphology is really important. And changes in waveform morphology may precede badness intracranially. So this is a normal ICP waveform, where you see P1 is bigger than P2, is bigger than P3. Everything looks beautiful. And all is good in the world. The ICP is 12. And then you start to see, what do we see here? ICP 15. May not really come to any sort of alarm or alert. But if you look at the waveform, you see that now the P2 amplitude is picked up. It should signify that, hey, maybe I need to pay close attention to this patient. And then as time goes on, you notice, oh, now the ICP is 26. And then in this case, the ICP has progressed so much that it's not even in this case, the ICP has progressed so much that all normal architecture is lost. So Golda went into a lot of detail already about zeroing and calibration. I just want to, again, point out that once the drain comes out of the head, it can go one of two ways. It can either go to the drainage chamber, or it can go to a transducer, which changes the pressure signals into electrical signals into a waveform and a number on your screen. So if it's close to the transducer and open to the drainage, so this right here, it's actually close to drainage, right? Because it's a three-way stopcock. So when it's close to the drainage and it's transducing, you will see a waveform. When it's the other way around, where this stopcock faces this transducer, then it's open to drainage, and you will not see a waveform on your screen. But you will be draining CSF in that case. So I just wanted to point that out. And yes, this is the picture that I was talking about, about inter-parenchymal monitor drift. So this is a patient who had a right and a left interparenchymal monitor. And you can see that initially, yeah, there's a little bit of a pressure difference, under 5 millimeters mercury, acceptable. But however, when time goes on, you see that that drift then becomes 20 millimeters of mercury. And then you're not really sure which one is more accurate. So how do you present a patient who has an EBD? What are things you want to think about and mention? So the ICP waveforms, we talked about how important the morphology is, how much CSF they've put out, what color the CSF is, the placement on the most recent head CT. And then if any of that has changed, then obviously error in the circuit is never good. So there's two different ways to drain CSF. One is continuous drainage. So again, remember when it's a three-way stopcock, so it can go one of two ways. So if you're continuously draining CSF, then you're only intermittently closing it to drainage to transduce the number. So in that case, you're only intermittently monitoring the numbers. The other way is you are continuously monitoring their ICP and then only draining their CSF intermittently. There have been studies that compared both approaches. And there was one Japanese study that is attached here that you can feel free to read that found that intermittent drainage may be more effective at reducing secondary hydrocephalus, but it shouldn't be used for primary hydrocephalus after aneurysmal subarachnoid hemorrhage. And oh, the Brain Trauma Foundation also recommends continuous CSF drainage. So in our institution, we use continuous CSF drainage. Okay, so lots of words here. They're mainly there for you guys to read through later, but things I just, key points that I wanted to point out. Avoiding routine CSF sampling. The collection system should only be accessed when absolutely necessary. We, you know, recommend one dose of antimicrobials before the EBD is placed. Typically, you know, ANSEF is used in most institutions. We recommend using antimicrobial impregnated catheters. Golda mentioned that. You know, we don't change out central lines routinely. We don't also change out EBDs routinely. We don't recommend that. We recommend using an EBD management bundle. I know Golda went into a lot of great detail about that. VTE prophylaxis is recommended in patients with EBDs. So what are some of the emergencies? So a patient had, you know, clear draining CSF and then all of a sudden, bright red blood. That should be a major red flag. New blood in the EBD should be very concerning. In this case, this patient had, you know, a large recurrent ICH. Okay, and what if the EBD is not draining? It could be for a variety of reasons. You know, any blockage within the circuit can result in this. So it really has to be troubleshooted to see what the problem is. One of the things we do is, you know, we look at the circuit to see if there's any obvious air bubbles, debris, check the filters, make sure everything is connected, and then if all of that checks out, then carefully lower the entire drainage system. So remember Golda went over how CSF drains based on the bag height. So the EBD is set at five millimeters of mercury. It will only drain when their ICP exceeds that amount. So maybe they're not draining because their ICP is between zero and five versus is the EBD not working. How would you know that? So one thing you can do is you can lower the bag height and that'll tell you, you know, now you're like, you know, minus five millimeters mercury. So even if their ICP is two, they should drain. So that'll, and then if they drain then, that tells you that their ICP is just low, but the circuits actually paint. And this is just in a close-up examples of what we talked about. So here it's close to drainage and open to transducing. So you should see numbers and waveforms on the monitor. And this is close to both. And this is just an example of bag height. So how do you know, you know, you hear neurosurgeons say like, hey raise the EBD from five millimeters of mercury to ten millimeters of mercury today. What does that mean? So how is that done? So again, you're changing the resistance to which it drains. So if you're going from five, from, it looks like maybe zero to fifteen in this picture, you are basically changing how much resistance against which it drains. So here that it'll drain as long as their ICP is greater than zero and it'll only drain when their ICP exceeds 15. And the bag height has just changed. So you'll see the whole chamber increase in height and then sort of point that way. So when you you're looking for this marker, when you're looking for a bag height. So when do we start weaning EBDs? Typically, you know, resolution of the underlying problem or need for intracranial pressure monitoring. If their, if their CSF is clear, if their CSF output's been less than 250 mls in 24 hours, and they've had a stable neurological exam for 48 hours. So lumbar drain is basically when, when it's placed, it's like doing a lumbar puncture but instead a catheter is put in at that area. Beautiful. Okay, it's back. Catheter is put in in that area and then attached to a EBD system. And there was an article that came out last year that looked at, you know, compared in aneurysmal subarachnoid hemorrhage patients, compared just CSF drainage through EBDs to drainage with EBDs combined with lumbar drains. And the patients that had the lumbar drains actually did better. And the thought is that, you know, gravity helps the blood to drain out more through the lumbar drain and maybe less neurotoxicity. Those are pictures of the lumbar drain going in. Okay. All right, so indications for lumbar drain catheters, acute brain injuries such as TBI, ICH, subarachnoid hemorrhage, hydrocephalus with ICH, transpinoidal resection of pituitary tumors with or without CSF leaks, aortic vascular surgery to increase spinal cord perfusion, interspinal cord artery ischemic infarction. And then push to have potential complications. You know, any time you're accessing anything, so pressure always goes from where it's higher to lower, so if you have, you know, really high intracranial pressure and you're introducing a lumbar drain, potential, there's a potential for downward herniation, bleeding, infection. If you're draining too much CSF, there's always a potential for subdural hematoma. Again, infection, meningitis, subcutaneous infection, and catheter malfunction. Some important trials that you can peruse at your leisure. So some non-invasive evaluations using transcranial dopplers. The transcranial dopplers offer a window non-invasively, so this is an example of MCA being incinated. So you see that in a normal patient, there's, you know, a nice upstroke that's rounded, and then there's a significant diastolic portion as their ICP increases, their systolic peaks becomes much more resistive, meaning, you know, sharp peaks, and then their diastolic flow is much less, and then as their intracranial hypertension worsens, you may see reversal of the diastolic flow, and that's abnormal, right? Unlike your brachial artery or, you know, peripheral artery, the brain requires continuous blood supply both in systole and diastole. So having diastolic flow reversal is very abnormal and signifies intracranial hypertension, severe intracranial hypertension, and impending herniation, and does not, you know, these two waveforms when sustained are not compatible with life, but offer a potential for treatment. So as ICP worsens further, you're only seeing the systolic phase, and then eventually no flow visualized in both in either systole and diastole. This trial looked at non-invasive monitoring of ICP using TCDs versus invasive monitoring, and here's the formula that they used to convert non-invasive to invasive, and they had a pretty good correlation. Another surrogate to look at intracranial hypertension is optic nerve sheath diameter. Remember, cranial nerve 2 is surrounded by the meninges and the subarachnoid space, so if you have raised ICP, it actually communicates with the optic nerve sheath, and it can be measured. If you're looking here, so most of the optic nerve sheath dilation happens in the retrobulbar area, so typically we measure it three millimeters from the retina, and we measure the diameter there, and you know there are studies that show really high ROC or really high correlation with invasive parameters. This is a really neat infographic, credit to Nick Mark, but you know we won't go over it obviously, but it summarizes a lot of what we talked about all on one sheet. Okay, so we're ready for any questions that you guys may have. Any recommendations for antibiotic prophylaxis for the duration of EVDs? So anytime you're giving antibiotics, you always again have to weigh like the pros and cons, right? So for placement, it is recommended to prophylax. However, for the duration of the EVD, you know there's no recommendation for continuous antibiotics, and you know it might increase your complications of more resistant bugs, etc. So just like you know we wouldn't treat a pneumonia before it's a pneumonia, I would say that a hypothetical infection in the brain, especially when you don't know who's going to develop it, we don't typically treat for that ahead of time. Hey Swarna, it's Laurie Shutter. I just emphasize that you're absolutely right. Regarding prophylaxis, just to be a little clearer, it's the usual pre- operative type prophylaxis of giving one gram of ANSEF within one hour of the insertion of the catheter, and that is all you need for prophylaxis. You don't have to continue it, and in fact there's you know most people would say absolutely not for exactly the reasons you said. We don't want to continue it. There are, as you mentioned, a lot of antibiotic impregnated catheters. Those can be costly, and not all institutions have those. So I would say if you don't, it doesn't mean you have to go buy them, but there's some older literature saying that typically the risk for infection starts climbing after about 10 days. So you do need to start being careful at that time, and just recognize that if somebody's having bad fevers, you can do surveillance of the CSF after that time period, but we actually we require a full sterile setup if we're going to draw CSF, and only our nurses are allowed to touch it. The nurses won't let the neurosurgery residents draw CSF for cultures. They don't trust them to be sterile enough. The nurses are the only ones that draw CSF for cultures. Thank you for sharing, and great points. Thank you. I see some questions in the chat, and it says, how do you manage agitated patients who have EVD or ICP monitors? I think I can answer that. So we typically don't like to put our neuropatients on sedation, right, because it becomes very hard to tease whether their somnolence is due to their neurostatus, or if it's the medication. So most of the time, patients with EVDs will end up having a one-to-one, having a sitter with them. So they'll be placed on one-to-one observation, and you literally have somebody in the room with them so that they can help calm them down, you know, they can also help prevent them from touching the EVD, etc., etc. I've seen that happen many times in my place of work, because most times, you know, patients are in bed, they become agitated, sometimes they lose track of time, and they start becoming very impulsive. So the one-to-one monitoring seems to work quite well. You know, if need be, and they need some sort of sedation, it will probably be like a low-dose Prestidex, which I've seen used before as well. But mostly, we try to refrain from sedatives and utilize the one-to-one sitters instead. Great, thank you. I see a few more questions have come through. I'll try to get to as many as I can within the time frame. Is there any way to monitor pressure and drain fluid at the same time? So great question. There are EVDs that actually allow both. They are not common. We don't have it in our institution, for instance, but technology is heading that way, and it is a possibility. Next question, any special considerations when transferring patients with ICP monitoring and for lying a patient flat for CT? Excellent question. Okay, so I'm actually going to pass that one to Golda, but I'll just say that, you know, laying the patient flat for CT, you always have to think about intracranial hypertension. If they already have a half-high ICP, you may want to pre-treat them. We typically, when we travel, keep the head actually up until the very moment that they have to lay flat for CT or for NGO or whatever the need is, but I'll let Golda weigh in on how that's actually done to ensure the patient is safe. Yes, Swarna, I totally agree with you. I mean, that's what we do. Typically, if it's a patient who's known to have crises, you know, we try to make sure that we pre-treat ahead of time. However, like you said, during transport, the patient's head of bed is kept at least 30 degrees or greater, right, all throughout the scan, I mean, all throughout the transport. Once we get to our destination, which is either CT scan or MRI, then, you know, for CT scan, because it's relatively short, usually we'll just keep it clumped, right, because it's not that long. However, for an MRI, that might take up to 30 to 45 minutes. What we'll do is we'll actually bring the EVD into the patient, you know, in the MRI suite, level zero, and then just have it open during the study. This way, you know, there is an increased intracranial pressure and we're draining appropriately. Perfect. And many people will clamp. You saw that, remember in the slides, you saw two, three-way stopcocks. So one is proximal to the patient and one is near the EVD setup. So they will often clamp both just to make sure, you know, you know, they don't forget and there's no room for error. So when it's clamped for travel, typically both are clamped. Can you comment on cerebral microdialysis on one of the slides? Yes. So cerebral microdialysis offers sort of another way to look at, look at, you know, the metabolic infrastructure of the brain. So some of the common parameters you can monitor, lactate, pyruvate, glutamate, glycerol, and they can, you know, signify neuronal death. They can signify, you know, cerebral metabolic crisis. And sometimes even when there's, you know, there's TBI studies, even without cerebral ischemia, meaning even though it's not necessarily a delivery problem, the blood is flowing, the oxygen, oxygenation of the blood's okay. And, you know, brain O2 is, tissue brain O2 is okay, but they could, the cells could still not be able to utilize that oxygen effectively. And that can be detected by cerebral microdialysis. So metabolic distress is sort of the term. So these are sort of on, these are sort of early things that can alert us of, of damage that's ongoing. So we can treat it before, you know, a large amount of neurons die. So that's kind of the whole idea of multimodal monitoring is to combine different aspects of neuromonitoring in order to detect secondary brain injury as it's happening in order to limit the brain damage. So wonderful question. Next question. I agree not to treat ahead of time. Same as having a Foley, we don't start prophylactic antibiotics, even impregnated catheters. Thank you for that comment. Any considerations when parenchymal monitor is preferred over ventricular other than slit ventricles? Yeah. You know, when there's global brain injury and you are just, you're not requiring CSF drainage, an intraparenchymal monitor would be, would be perfectly acceptable in that scenario. For instance, I can tell you that our guidelines for invasive neuromonitoring are pretty broad in our institution. And there really anyone in a coma that's not rapidly reversible with a low GCS and, and, you know, don't have any of the exclusion criteria that we talked about. And in those cases, we do, we do intraparenchymal monitors. So as long as they don't require CSF or require, have a need for intrathecal medications and have global brain injury, I think intraparenchymal monitor would be a perfectly all right alternative. Lumbar drains should technically have a lower risk of drain related IPH. Should they be used preferentially over EVDs? That's a very interesting question. I would say that, you know, that study that I talked about in aneurysmal subarachnoid hemorrhage patients that had lumbar drains versus the standard of care, which was just EVDs. And, you know, in, in them the outcome was, was improved. I think that's a, you know, strict subpopulation that, that has been studied. I would say we don't have data in other populations of acute brain injury, but it's an interesting question. I would caution that, you know, if there's a, a lot of like intracranial, if you have a profound intracranial hypertension, the risk of downward herniation is, is there with lumbar drain placement. So that has to be weighed with the need for the intracranial pressure monitoring. Another question I see is, is there any evidence for looking at the area under the curve on the ICP waveform to help with decompressive craniectomy, for example, with TBI? Oh, interesting. So making a treatment decision, this question's about making treatment decision for decompressive hemicrania based on the area under the curve. So it's a really interesting question and asks, is it, it's a question geared at the ICP morphological changes rather than the ICP number alone. And I really like how you're thinking. I would say that practically, in a lot of places, they don't have access to the statistical software and the complex platform that provides real time area under the curve in order to make that operational. I think it may be available in certain institutions and it's a really cool idea. I would say that, you know, practically in a lot of places that might be challenging. But I would let, you know, invite any of the other moderators to weigh in on that. I think it's going to be a future focus. I think we have to look at the burden of the ICP rather than just a raw number. So great answer, Swarna, but I agree that this is a future type option of being able to actually look at the overall burden of ICP waveform. Great. Okay. I'm trying to see, Golda, do you see any other questions? I saw this one that says, how do you calculate CPP when some folks measure ICP in centimeters of water and some measure it in millimeters of mercury? So in Swarna's presentation, she did talk about a conversion factor from millimeters of mercury to centimeters of water. So since your CPP is your MAP minus your ICP, if we convert the millimeters of mercury to centimeters of water, we should be able to arrive at a CPP for the patient. So that's what I would do. Great. Thank you. Can I ask a question to everybody online? Please. So where should you level the A-line to measure the CPP? Level it at the tragus. And does it matter? And does it matter? What are your thoughts, both of you? To tell you the truth, I have never even considered that. A-line is always at the phlebostatic axis, EVD is always at the tragus of the ear. But that is a very interesting question. I have to think about it. I think it does matter. But I think the studies haven't accounted for that difference. So a lot of what we know for our goals are based on them being leveled differently. So I think we'd have to study it at the same level. I think it matters. I think it's a future goal. That's my view. I agree. Great. I think the why Olson has spent a considerable amount of time looking at this. He has quite a few papers on where the blood pressure cuff is level. He took a survey of practices across different ICUs. He's talked about whether ICP, EBD zeroed at Fragus or some people zeroed EBD at the heart level as well, same as the blood pressure cuff. So if people want to look up his name, I think he's done a considerable part on the nursing considerations on how the ICP is actually measured. Yep, great points. Thank you, Aarthi. All right, I think this concludes our Q&A questions. I don't see any more. Thank you so much to Golda and the rest of the panel and thank you for the audience for attending. Again, this webcast is recorded. The recording will be available within five to seven business days. Log on to mysccm.org, go to the My Learning tab, click on the Neuromonitoring at the bedside course and the access button to access the recording. That concludes our presentation. Thank you so much for your time and all your interesting questions. Thank you. It was a pleasure. Thank you.

Neuromonitoring

Neurocritical Care

Intracranial Pressure

External Ventricular Drains

Subarachnoid Hemorrhage

Hydrocephalus

Invasive Monitoring

Non-Invasive Monitoring

Cerebral Microdialysis

Neurointensivist