Chad Ball 00:12
Welcome to the Cold Steel surgical podcast with your hosts Ameer Farooq and Chad Ball. We’ve had the absolute privilege of chatting with some amazing Canadian as well as international guests over the past year. While the topics have been broad in range, whether clinical, social or political. Our aims for the podcast continue to remain the same. We hope to inspire discussion, creativity, scholarly research, and career development and all Canadian surgeons. We hope you enjoy our second season as we continue to highlight some incredible guests, deliver detailed masterclass sessions on a myriad of clinical topics and introduce some fresh new features such as debate and companion formats. We hope you relish the podcast as much as we do.
Ameer Farooq 01:13
This week we had the pleasure of speaking with Dr. Mark Hamilton on the podcast. Dr. Hamilton is a neurosurgeon at the Foothills Medical Centre in Calgary. Dr. Hamilton helped us walk through a number of neurosurgical issues that are pertinent to general surgeons, such as hydrocephalus, the role of craniectomy in traumatic brain injuries and DVT prophylaxis in patients with traumatic brain injuries. As always, send your comments and feedback to email@example.com. Dr. Hamilton, thank you so much for joining us on the podcast. We really appreciate you taking out the time to come and join us and speak with us on a really important topic that we share across our specialties. Can you tell us a little bit about yourself where you grew up and your training pathway?
Mark Hamilton 01:59
Sure. Thanks for inviting me. It’s a real pleasure to be here. So I grew up in a relatively small town in northern Ontario, north of Sudbury. Population, I think max at about 4000. And then I went to University of Toronto for my undergraduate degree then to McGill for medical school. And then I was actually in the armed forces for three years. I went through med school with medical officers training program, or training plan I think they called it. I went to Ottawa for three years. I ended up doing two years of cardiology as part of my service then as part of the reward for my three years due, I got my equivalent of an R two year of general surger. I did my first year as a rotating intern at St. Paul’s in Vancouver before I went on to Ottawa. And then I came to Calgary to do neurosurgery. I did my neurosurgery and then went to Phoenix, Arizona to the [inaudible] Welsh institute. I did a fellowship in skull blades and vascular and then stayed for an extra six months and did a fellowship in pediatric neurosurgery before coming back to Calgary in January 1994. Interesting transition when you move from Phoenix to Calgary in January betting your quite cold experience is an adaptation process that occurs when you’re down south. It was quite an adjustment. So, I started on staff working with pedes and adults, but initially almost all pedes but very quickly started to develop an active adult practice in cerebral vascular and transitioned over time, to the point where now I don’t do pediatrics. I don’t do vascular disease anymore and I do proper health hydrocephalus, adult brain tumor in general neurosurgical. So I came to Calgary for my training for a couple reasons. One, my wife was doing pediatric residency in Calgary at the time. And I was in Ottawa finishing up my term in the military. And I liked the program because it had a lot of clinical experience and the people seemed very nice. And I thought it’d be a good experience and it was. It was a great residency experience. And then when we went to the States, my wife was doing pediatric emergency medicine at the Children’s Hospital. We went to the states to do my fellowship. And then we’re looking at jobs in the US and Canada. And an opportunity came up in Calgary. And that’s how we ended up back in Calgary. We have, you know, like most people look for a place that has a good program, a place where you can do the work you want to do. And if you have family nearby, that’s a bonus. And so we have family nearby, and there was a reason to come back. So that’s what we did.
Chad Ball 05:27
So interesting. You know, for Hamilton, you were obviously as you mentioned, a primary pediatric neurosurgeon for a very long time. And we were curious, how was that? How did you like that? How did you frame that? And I wonder, do you miss it?
Mark Hamilton 05:43
Yeah, I mean, I liked pediatrics, I always liked pediatrics. Before I even went away to do my fellowship, When I was offered the opportunity to do pediatrics, it was with the assumption that I would do pediatrics and adult neurosurgery. And eventually, that became a taxing venture. Because there were years when it was basically full-time pediatrics and full time adults, with not much in the middle. And it was pretty busy. But pediatrics is like a different world. The entrepreneur surgery is a different different world. And I really enjoyed it. I eventually made the transition to full adult practice because of the need for a transitional process in pediatrics. When I arrived in 1994, Terry Miles was the only pediatric neurosurgeon in the city and was exhausted. And so we needed to build a program that was sustainable. And having me hang on to the last minute was not going to allow that to happen. So I was willing to make that transition. And at the same time, I was also developing this interest in transitional care. And over the years, by just the way things were set up, I looked after patients that I first got involved with when they were children and then when they became adults, I assume they were cared in my adult practice. And started to do more and more adult hydrocephalus and then realized that there was a huge gap in the care models for this patient group. And so when I made the transition it was knowing what I was going to be developing was something that I already had a foothold in. And do I miss pediatrics? Absolutely. Really. It was a wonderful experience. I enjoyed it. I enjoyed the people. I enjoyed the families. I sort of reached the other end of the spectrum because now I’m my practice is around the geriatrics. A huge part of my practices has now become geriatric. So, I used to see children with their families. Now I see patients with their children much more commonly.
Chad Ball 08:12
You know, I’m glad you brought up hydrocephalus. And maybe we can drill down on a couple of questions related to that before we talk about head injuries. I’m curious. You know, my sense is that hydrocephalus is a diagnosis that’s missed consistently and often and, you know, both by families and primary care physicians as well specialists. So I guess the first thing is, what sort of things do you look for maybe as a non neurosurgeon in diagnosing hydrocephalus?
Mark Hamilton 08:43
That’s a good question. Whenever I end up talking to somebody about hydrocephalus, I step back and say, you know, if we talked about adult hydrocephalus, we’re not talking about one disorder. And the problems and challenges vary from subtype to subtype and a number of years ago, I proposed a rather pragmatic organizational construct. And it helps because each of these groups have different different issues. So one group has the patients that were diagnosed as children. So they transition to an adult in a hospital care, clinical care environment. Those patients typically carry different issues related to their shot management, different risks for many of them when their shots fail. And they, I think, a higher percentage when their shots fail, they get into more acute situations, because some of them are extremely shot dependent. They also have a noninsignificant number of them showing up with pseudocysts in the abdomen, which you have to be aware of and look for if they come in with shot failure. Then there’s a group that is acquired hydrocephalus. And these are the patients with sub requisite number of brain tumor trauma. And they, you know, they’ve always been around so to speak. I think people have always sort of recognized that this occurs. But there’s different strategies that exist on how people approach management. And if you look at the literature, for instance, on sub arachnoid hemorrhage and shot dependency, you’ll see that it ranges from anywhere from about 5% to 50% in studies. Very retrospective, often without defined protocols. So there’s a lot of work that needs to be done in sorting those out. And even the management of our next drain in the sub arachnoid hemorrhage, population with hydrocephalus, or initial hydrocephalus and ventriculomegaly is not very well established. When it comes to brain trauma, same issues, as people try and figure out is this the brain trauma result? Is this the hydrocephalus now becoming an issue, result of the changes on the scan rate of atrophy or inability to progressive. Ventriculomegaly nourishment because they can’t manage their CSL. So that’s a whole group. Then the third group is this group of patients who presented in their middle age, so anywhere from depending on what you define as middle age, usually, it’s sort of in the 40s to early 60s. Quite the average is about 55 to 58. These are patients who have unrecognized previously undiagnosed ventriculomegaly hydrocephalus. And they present sometimes because they’re found with big ventricles. Because they’ve had a head trauma, or CT for headaches. They get referred because of big ventricles, or they have progressive memory problems, which is a significant issue in this group. Some of these patients require intervention and some of them require observation and longitudinal care to determine when they might get into trouble. But we have a process to sort that out. The message that we give to care providers in the emergency room is via somebody with big ventricles. We’d rather see them and sort out whether this is an issue for them rather than miss them. When you miss these people, they show up in their late 60s early 70s, with quite significant, profound dementia, often not reversible by that time. Then finally, the fourth group is idiopathic normal pressure hydrocephalus group. INPH – for some people is a controversial diagnosis. That’s based on old literature, old understandings. And INPH, this is the elderly patient, the definition usually we use the age about 60. For the average age, when you look at this group is somewhere around 75 to 77. And this group, they present with this nonspecific triad. So it’s a gait disturbance, cognitive disturbance in bladder urgency and frequency. And you have to put those three out there, as you know, when you’re talking about 75 and 80 year olds, people might say, well, no, that can be just old age. But this is a progressive problem for these people. And they almost always have to have gait. And by gait, I mean balance, instability, slowing and shuffling of gait. And for cognitive issues, it really depends on where you intersect with the person in the time person or disease. And bio-urgency and frequency are. People usually asked about incontinence, but usually these people have urgency and frequency and the incontinence comes often when they just can’t mobilize fast enough to get to the washroom. So it’s a diagnosis that needs to be sorted out. It’s often missed because it’s attributed to old age. There was a interesting study done a number of years ago where they went to three nursing homes in West Virginia, and they looked at just the patients who had a symptom complex that would suggest, you should at least investigate with a CT scan or induce rebreather mask investigations. 10% of the group met the basic criteria had it not been investigated. We were doing a project looking at the epidemiology of hydrocephalus with the Public Health Agency of Canada. What startled me was the number of patients who end up in nursing homes. This is across Canada and probably across North America. Who never had a CT scan, got a diagnosis of dementia. Don’t have a CT scan, they’ve never seen a neurologist or neurosurgeon, but they have dementia. And if you walk out into a crowd, and I think you ask people, you know, what does dementia mean to you, it would be Alzheimer’s disease. So by default, these people get labeled as having Alzheimer’s disease. And INPH is potentially reversible if you identify it early enough. And there are processes that we are comfortable with in terms of undertaking that mission. So the message basically is, if you are elderly and you’ve got cognitive gait issues, don’t dismiss it as Alzheimer’s disease. If you’re middle aged, and you’ve got cognitive issues, don’t dismiss it at all. Those patients need investigation. The CTMR, and if you are a transition patients, you need someplace to look after you for the rest of your life. Because when you become an adult, your problem doesn’t go away.
Chad Ball 16:04
You know, one of the things you briefly mentioned in chatting there was the EVD and you know, your hydrocephalus practice is obviously internationally renowned, and you’re a famous guy for that reason. And I also realized that the peer reviewed publication is not out yet. But you’re doing some really interesting work with the general surgery side of things in terms of laparoscopic placement of VP shunts. Can you touch on that and sort of why that’s been so helpful, particularly with regard to shunt obstruction and failure?
Mark Hamilton 16:36
Sure, absolutely. So, when you look at hydrocephalus in general, people still think it’s a pediatric problem. When you deal with kids and shunts, when shunts fail, they tend to fail approximately. So a shunt is made up of three main parts: a ventricular catheter, a valve and a discipline catheter that goes either into the abdomen, or potentially into the superior vena cava atrial junction. So, when you look at kids, it’s proximal failure. When you look at adults, especially older adults, it’s distal failure. And proximal failure occurs very infrequently. And there’s lots of reasons that we go into to explain that, but just recognizing that and not doing something about it, you end up with just a failure rate that approaches 50%, at three and a half to four years. And that’s local experience. When we started looking at prospective data. We’re doing a systematic review of meta analysis of shunt failure in adult patients. When you look at that literature, the first message from the literature is horrible. Because it’s very poorly done. You end up with less than 100 papers where you can extract data. And the data suggests that there’s a 15% shunt failure rate at six months. That’s all adults. So that’s four different disorders. So shunt failure is a common issue. And so one of the things we started doing and I ended up collaborating with you Chad, as you’re well aware of, we started looking at what can we do with the distal end of the catheter to avoid this complication. I was doing more shunt revisions than I was shunt insertions. So if you do longitudinal care, and you put chunks in and they fail, you end up revising them, and then they’ll fail again, and you keep revising them. And these operations were removing the catheter and simply putting it back in the belly. So it wasn’t that they were plugged, they were in a position where they couldn’t drain properly. And the traditional method of doing a catheter insertion of a shunt is simply to make big old mini laparotomy which is really mini. And you end up getting access to ventral cavity and you just slide the catheter which is coming down subcutaneously into the peritoneal cavity, and then it just flows freely. So NPH patients for instance, don’t have high driving pressures to their shunts. Very easy to create distal back pressure and block their shot. So there was a paper published a number of years ago using what was called the “falciform technique”. And it was a retrospective series of 50 or 60 patients and they they use the laparoscopic approach to have a catheter come in at the level of the Zippy sternum, and then they colonate the phosphor ligament and tuck it behind the liver. And then that would keep it away from the omentum and the other things that could potentially obstruct the shot. So we started doing this, we had to learn and modify as we went along as the instructions were, in the technical issue, were not very well elaborated. And we did a prospective series of consecutive patients. The shunt failure rate doing that. And also, I added the image guidance for the passing of the ventricular catheter, which is still done in the majority of places in the world freehand. Even though image guidance is available at most modern neurosurgical centers. And that combination and most of it, the effect is from the abdomen, drop the shunt failure rate to about 16%, in three and a half to four years. So very dramatic reduction in distal catheter failure rates, very dramatic reduction in the number of secondary failure rates. And by examining the characteristics of the abdomen, with a laparoscope rather than just blindly stuffing a catheter into the abdomen, we could document whether there were a lot of adhesions, a lot of scarring, whether there was a lot of momentum up over the liver that might block the distal catheter, even if we placed it in the optimal position. And with all that, I think we burned when patients, even when you think the abdomen might work, it’s just not going to work very well. And there’s an alternative shunt called the bhi where we’ve modified the techniques for insertion about one of the last remaining things we have to sort of struggle with is the fact that the catheters that stay behind the liver, the failure rate is extremely low. The catheters that we put behind deliver, some of them pop up very quickly. And those go on to fail at a rate that’s very similar to the non laparoscopic group. So there are things that could be further modified to improve this. But I think the number of patients in this series is about 240. But half of them before laparoscopic, and half of them after all consecutive prospective patients. So I think it’s a pretty large group, powerful group. It’s up, we’re just doing some revisions to the paper and hoping to be accepted. And as soon as we submit it, we’re also submitting a video equivalent to Joe Bay for review.
Ameer Farooq 22:43
One of the neat things about that work is how you cross different specialties and put the brains together with different specialties, to do things that we wouldn’t have traditionally thought of as something that would involve both general surgery and neurosurgery. So congratulations on all that really amazing work. We wanted to leverage your expertise as well to chat a bit about head injuries with our audience being mainly general surgeons. Aan you talk a bit about how to classify traumatic brain injuries for us? And let’s say someone comes into the emergency department who is found to have a traumatic brain injury? Who needs further assessment?
Mark Hamilton 23:23
Now, that’s a good question. You know, there’s lots of different classifications that are used. You know, clinical classifications, CT classification, you know, what is diffuse, focal, diffuse axonal, injury type of injury, pattern for the patient. I mean, I think most people end up classifying from a pragmatic viewpoint. Classify head injuries or traumatic brain injury as mild, moderate and severe. There’s different strategies for each of those groups, then you’re making that assessment of the degree of severity of the head injury, is it in the first hour? Or is it the first six hours? So the Glasgow Coma Scale, and most people are familiar with. So now Glasgow Coma Scale of 14, 15 out of 15 is usually going to be mild head injury, you know, 13 and below to nine, nine to 13 is going to be sort of moderate. And 8 and under, some people will call severe. There’s a bit of variability in how people use those terms. But that’s the general sort of construct. If you have a mild head injury, and then the other thing that you have to remember is that there’s all this group of people who have very mild head injuries, but to have consequences from those head injuries, and be classified as having concussionial injuries. So mild head injuries, by definition, usually with a normal GCS, and usually with a normal CT scan, and that’s how most people are assessed in emergency department, not with MR imaging, but with CT scans. So a number of years ago, probably eight or nine years ago, we were struggling with how do you define who needs to be at a tertiary care center in Calgary. For instance, at the Foothills Hospital, that’s where neurosurgery is based, versus who can be kept at another center without risk of them deteriorating. And we actually developed some guidelines, which I think, to this day, eight or nine years later still hold true. And we haven’t had any major issues that I’m aware of, in the use of these to determine who should or shouldn’t be at the center. I think when you’re looking at this, this would be a rather large topic, as you dive deep into it, but you know, symptom management, I think, for mild head injuries is important. You know, some patients may have a normal CT, but that can be very symptomatic, and may require some additional help in the emergency department. The basic things that led us to divide, we divided the patients into those that can do a phone consult with the center, give them some advice, and those that we required transferred to the Foothills Hospital. And this helps sort of organize you know, the severe from moderate to severe to the mild. So, you know, I think part of it depended on their Glasgow Coma Scale. So a mild injury, 14 or 15 for GCS, maybe had a small contusion on their CT or no contusion, small epidural hematoma, no shift, a tiny, depressed, fracture.Tthose are all sort of compatible with staying at a center. Usually, they might require and may require admission, but they don’t have to be sent to a tertiary center. And those patients will often just require symptom management. And one of the questions that we often get asked is will you repeat the CT scan, and that’s gonna vary depending on number of factors. And then they may require admission for one or two days for symptom management and to do a follow up CT scan. So for that group, the one we’re doing a phone consult, and then maybe admitted elsewhere. I think, you know, if they’re on antiplatelet agents, particular products, if they’re on anticoagulants, particularly doacs, they may be at a higher risk for expansion of the small contusions or hemorrhage may be a higher risk. There’s a lot of work that’s being done on trying to determine when you can not do a follow up CT scan, rather than even when you should do one, or can do one. Lots of people will still do one 24 to 48 hours later. I think that there’s probably future work that’s going to help sort that out and parse that a bit more. At times, I will make recommendations not to repeat a CT scan and go on symptoms, because it’s so miniscule and having a dot of hemorrhage does not validate the need to necessarily do a hemorrhage, if they’re not on an anti platelet or anticoagulant. If somebody is on an anticoagulant or has a slightly bigger hemorrhage or contusion, but still under that threshold, and I often recommend they do another scan. Patients getting transferred, then you’re starting to look at for people who have a clinically and moderately severe head injury such as you know, the Glasgow Coma Scale. Less than 13 or less than equal to 13 rather. And then they’ve got evidence of a bigger intracerebral hemorrhage, subdural hemorrhage, epidural hemorrhage, perhaps a midline shift. If they’re starting to get effacement upper basal cisterns on your CT scan. That usually means you know they’re running out of room and that’s a higher risk issue that they have multiple hemorrhages. Even though they may all be small, but there’s multiple ones, that’s something to consider. Compound across skull fractures is another category. A little depressed skull fracture, there is no required indication to elevate that. You can even, if there’s a laceration, clean that out, wash it out, sew it out. Some centers will give a dose of Ansep at the time to do that. But if it’s a compound depressed fracture with a large depression, they usually should be at a tertiary care center because they may have underlying contusions or frequently do have underlying contusions. Basilar skull fractures with CSF leaks shouldn’t be at the center. And then patients, as I mentioned, who are on anticoagulants, and significant anti platelet agents can be an issue. And then that’s basically how you end up determining who needs to be at a tertiary care center. And then that also sort of defines who’s going to be most at risk, potentially, for getting into trouble.
Ameer Farooq 30:44
You know, there’s often a lot of emphasis on the management of traumatic brain injuries. And I think that’s beyond the scope of what we’re trying to do today. But one thing that I think isn’t as talked about on lots of podcasts that I’ve listened to and in lots of resources that I’ve read. But that comes up quite frequently, when you’re in the middle of the night on the trauma service is when do you actually need to consider a surgical decompression? And sometimes I find that my, you know, my sense as a general surgery resident was often not aligned necessarily with what would happen to that patient, let’s say who came in with a traumatic brain injury. So how do you sort of think about the patient that needs a surgical decompression?
Mark Hamilton 31:32
That’s a good question without an easy answer. We always say it’s a case by case basis, but there are I think, some elements that are, you know, that there’s common elements that come into play. Hopefully I’ll keep this organized as we’re talking about it. I think a patient who’s got massively destructive brain injury, even with a subdural, they’ve got evidence of DeRay hemorrhages in the brainstem, for GCS, which is when pupils are blown. You know, the brainstem reflexes are bad, you know, they may or may not be on anticoagulant. That’s a whole other complexity that’s added to this. Those patients you really have to step back and say, you know, are you going to offer the main thing of value in terms of improving their outcome or survival? And the answer for many for almost all those is no. We tend to weight it a little differently depending on age. But at that end of the spectrum, I don’t think age is going to matter if your pupils are blowing, and your GCS is three. Doesn’t matter how big the hemorrhage is, certainly not going to help you. When you get to the middle ground, where you’ve got somebody who’s in the moderate severity, head injury, with GCS of 13 and under, those are patients where you’re struggling a bit more with or we struggle a bit more with. So it’s often you know, okay so what is their status of their pupils. If you have somebody who is younger, they often can’t accommodate the blood volume within other space to accommodate that. And there’s this doctrine called the Monroe-Kellie Doctrine that everybody learns about in neurosurgery when they start training. There’s only a few things that are in the head, the skull, brain, blood and CSF. You start adding one, and something else has to give. You can compensate up to a point, but then you can’t manage. There’s no more CSF to get out. And that’s when you start getting an effect. That might be herniation. Or you might have decreased several buffalo in general, because of high ICP and the clinical consequences increase. So a young person you’re going to see, you might see that the basal cisterns are more effaced and subdural or epidural might, even though they might be a better end of a moderate spectrum, might be more concerned and want to take that out. There is a I must admit a certain Gestalt about the size of the subdural, or the epidural. That will push you one way or the other. I find it sort of makes me want to consider surgery rather than observation. It’s different for subdural than even epidurals. Epidurals size is important, location is extremely important as well. So I did a paper with one of the neuroradiologist when I was a resident. We looked at the non surgical management of dural hematomas. And the only few patients in that series that deteriorated were people who shouldn’t have been watched anyone. They had epidurals in the middle fossa. Those are patients that are more you know, there’s a point where they can very quickly move to a go herniation below their pupil and deteriorate. So the patient who have an epidural hematoma, they may not accommodate the size there. Where as if you get a occipital region, epidural hematoma, you might accommodate that extremely well and be very capable of watching it. Acute subdural hematomas are usually associated with, you know, a more severe mechanism of injury. So these patients often it’s more motor vehicle accidents, acceleration, deceleration, there’s usually more injury going on than you see on the scan, there’s diffuse injury, autoregulation in the brain, blood flow is not properly disrupted. And those patients, especially since that population tends to be younger, you have to have a lower threshold for considering removal of a subdural in an acute situation, especially if they haven’t reached into that, you know, totally destructive things. And then into cerebral hemorrhages with trauma are not incredibly common. It’s usually contusions that blossom. You do get the occasional hemorrhage or cerebral hemorrhage from the trauma and those you just have to work on the overall exam feature size. And by size, you sort of end up trying to calculate the volume, and then determine whether surgery is warranted. Is it superficial? Was it deep? So all those factors come into play. One of the big confounders that has come up in the past number of years has been the introduction of doacs. And even just the use of paddocks over the years, patients who are on those agents, even though we’re starting to get access to agents that can reverse the effects, those patients become extremely challenging to deal with when they present, no matter how big your hemorrhage is.
Ameer Farooq 37:28
Sort of on a related note, how do you think about who needs an intracranial monitor? And how do you make that decision?
Mark Hamilton 37:38
Intracranial monitors, you can divide them into a number of different types. And then you can move from and then there’s the criteria, then the type. So just to make sure I don’t forget the type aspect. So the general sort of rule of thumb, and I think it’s a rule of thumb only, is that GCS eight and below, more severe head injury, should have an ICP monitor. And I would put quotation marks around “should”. So it really depends on if you’re a GCS of three, you know, we will look at other factors and, you know, they have to be dealt with, before we may consider an ICP monitor. Is there any recoverability that’s possible? If your GCS is eight, then ICP monitoring might be something worthwhile. It usually is worthwhile in terms of sorting out what’s happening to the patient managing their cerebral perfusion pressure, as part of that algorithm. So that becomes important for that patient group. And then above that, it becomes really, you know, it depends on where you are. You know, if your GCS is 12, it’s very unlikely you’re going to get an SMP monitor, or even need one. But unless you’ve got something that’s producing hydrocephalus, and we fear that you’re going to deteriorate. And not so much in trauma, but we had a gentleman who had a big basal ganglia hemorrhage, and he was in the process of rapidly deteriorating. And it was all hydro related. So the potential is there with trauma, if you get some intraventricular blood to block your aqueduct, it can give you hydro, in which case their GCS is going to head there, but if the ventricles are enlarging, you have to consider that as a factor earlier on. And it’s not something that is universally agreed upon, using GCF eight and below, but it’s a point, I think you can sort of start to think about patients who hover around that, above 8, probably, you know, you have to be a little more selective. And below eight, you should be doing much more often. So the type of monitors are also relevant. The type of monitors also very relevant. So there’s there’s an external ventricular drain, which is a catheter that was placed into the ventricular system. And it’s hooked up to a closed draining system. So you can monitor ICP and remove CSF. So as I mentioned, with the Monroe-Kellie doctrine, you only have three things in the brain: brain, blood and CSF. So you can potentially remove CSF. So it can become a diagnostic therapeutic tool. Then the next most commonly used thing is the intergrain, como monitor. And there are different companies that have these. Codman, for instance, makes one and it’s got a transducer on the end. You just simply put it into the crank Come on, two centimeters or so in, and it can read ICP. But it cannot provide any opportunities for therapeutics. You can’t remove CSF with it. So, people, I think that EVDs, people will approach you and EVDs as having the benefit of therapeutics. But the challenge in somebody with a head injury is hitting small, or normal ventricles. And obviously, our neurosurgery residents tend to do these often in the ICU, they become very good at it, because of the teaching that occurs and standard methods that we use. But these are done without anyone’s guidance. These are done by using landmarks. And looking at the CT scan. And even for the ventricles. If you look at the literature, the failure rate for hitting the ventricles is not insignificant. And the number of patients who require multiple passes of a catheter to actually tap the ventricles is not insignificant. The risk of infection from an EVD is not insignificant, it probably approaches anywhere between five and 15%, depending on how long the catheters in, and whether you use a standard infection reduction protocol, like they would do for central lines. That’s generally absent in many centers. So the infection rates are all over the place when you look at the literature. So EVDs carry a higher risk, but offer more potential benefit. I trained when I was in Calgary as a resident with a very non-interventional approach to traumatic brain injury in terms of ICP monitoring. And I actually think we should be doing this monitoring. And we should be doing it within the parameters I outlined. Because I think it does give us a lot of advantage. Literature tends to support that. I think otherwise you’re flying blind. When I was training, we were told to use sequential CT scans. I think that’s like, you know, taking snapshots of a grade that’s 12 miles long, every two minutes. You’re going to keep missing things. So, you miss opportunities if you use that kind of approach.
Chad Ball 43:25
Yeah, that’s a good way to look at it. I think that it makes total sense. You know, the other thing I wanted to ask you, in terms of intervention, maybe at the opposite end of the spectrum was about craniectomy or leaving the bone flap off and it was a question I had for you because certainly in traveling internationally, to various places doing you know, the visiting prof Grand Rounds thing. It seems that the rate or the the fervor for doing craniectomy is massively variable in neurosurgical groups from trauma center to trauma center. So I’m curious what the foundational realities of that procedure are as well as the variability and what would explain that.
Mark Hamilton 44:04
Yeah, that’s a really good question and one that people have tried to answer unsuccessfully. There is incredible variability. I would agree with that. I think there are two big clinical trials that were done. Both of them dealt with fighting. I think most of them were patients with bifrontal craniectomy, decompressive craniectomy. Most of the patients were further down the road in their treatment process so these were not decompressed for an epidural or a subdural, leave the bone flap off. These are patients who were being mad as their ICP got out of control and then they went on to do a decompressive craniectomy. That was the rescue ICP trial and the Decker trial with the two. They answered things, and they created a lot of questions. I think, even after these two randomized trials, we’re left with a lot of uncertainty about the the actual real benefits in terms of outcome when we do this. I think part of the controversy is what is a good outcome? Is it survival? Or are we really looking at outcome measures that really say these patients don’t just survive, but they actually have a quality of life survival that makes it worthwhile to go through that. There’s a very well done paper, it was in Neurosurgery in September of this year. And it was an update on the guidelines dealing with decompressive craniotomy. And they actually, at the end, put together a section where they titled it “Incorporating the evidence into practice”. And even that was almost a page long as they tried to sort of manage the issues. They concluded that, you know, basically forming a decompressive craniotomy is not a simple decision. And the benefit should be balanced against the complications and likely outcomes on a case by case basis. So, after all that effort, we’re still I think we haven’t moved the dial that far forward. And there is a lot of individual center bias about the value of decompressive craniotomy. And doing the craniotomy is only one part of it. You have some patients before you do it, and they will experience brain herniation and wait for the defect, which ends up damaging that part of the brain. That plays into the issue of survival versus quality of life and function afterwards. And then at the end of the process, you have to turn that bone flap. You have to go cranioplasty. So usually doing a decompressive craniotomy, we crease the bone flaps, there are centers where they live in trauma flaps, they’ll put them into the abdominal wall, just bury that and then take it out at the time of surgery. The major issues with returning a cranioplasty, returning their bone flap is the major issue is infection. The second major issue with resorption. So the infection rates, when you look at the literature are pretty significant, probably five to 10%. And then you start getting into what do you use to replace it if you don’t use the bone flap or if the bone flap is infected. There are pre-made cranioplasty; pieces that you can model. You can get custom made ones, and there’s a growing interest and literature and small series on people in centers that 3D print their cranioplasties to put them in. The form fitting custom on this is that it really does make a difference in terms of ease of the operation and the cosmetic appearance. There’s a lot of literature that comes out a lot of literature gets submitted regarding decompressive craniectomy in terms of managing the downstream effects and returning it back. Putting back the clap. And then there’s also the issues that occur in the middle. There’s this syndrome called the center of attention find where they get a sunken appearance on their craniectomy side, like to the point where you can literally pour water and have it collect in the defect that happens, the brain collapses away from it. It has a number of different names but that can be quite symptomatic in some patients. And we’ve seen some patients who when they get their bone flap put back actually start to improve after that, because that may have been hurting them as well. So again, it’s a very complicated issue that needs a lot more work to sort through it. Bottom line is, I think decompressive craniectomy plays a role, I just do it on a case by case basis. I don’t know any better based on my review the literature. Timing is important, just for all these two studies and others have not really dealt with doing a craniectomy for kids up you’re gonna tell them leaving the bone flap off at that time. That’s just not the literature. It’s not really good on that. There’s been no prospective trial that I’m aware of. And then. So knowing when to intervene is really important if you’re going to intervene. You wait too long, the damage has been done. If you operate too early, you’re doing it on people that may not need it. And then dealing with the consequences of having done that operation, you have to at some point, replace the bone flap, do a cranioplasty and manage those potential complications and the symptoms that may occur in between those two events. As the patient’s getting better, but still suffering from the consequences of the cranium, or the decompressive craniotomy.
Chad Ball 50:34
The last question I want to ask you, before we part ways, and again, thank you for your time, surrounds I think another area that really is not so sorted out in the literature or in or in CPGs in general, which is the use of chemical DVT prophylaxis in patients with moderate TBIs and sometimes severe TBIs. And you know, my anecdote, I don’t mean it to be offensive to anybody. But often, in many of the places I’ve trained in, and also worked, seems to be up to maybe a junior neurosurgery resident who will just sort of arbitrarily say 48 hours or 24 hours or 72 hours. And I certainly realize in having delved deep into that literature that it is all over the place. But, you know, I do wonder a little bit when I reflect on the general surgical trauma side and we’ve become in the last 10 years really aggressive about chemical DVT prophylaxis. And I remember the days as do you, I’m sure, when you would crack your spleen in a grade 4 injury, and you’d be on bed rest and the whole rigmarole and you wouldn’t get DVT prophylaxis at all. Well, now you can split your liver in half, you can split your spleen in half. And we’ll generally give that post admission day one in the morning and away we go. And you see very, very rarely any issue with that. So I was wondering if you could frame the current status and the current beliefs as best you can with regard to chemical DVT prophylaxis for TBIs?
Mark Hamilton 52:03
Another good question. And it’s about as well sorted out as the decompressive craniectomy issue. I’ll give you some. So this is an area that I’ve been interested in for a long time. And I haven’t delved tremendously into the trauma literature recently. But when I look and go back when I was a resident, I was interested in DVT, and DVT prophylaxis. The consequences from DVT and PE. I didn’t mention earlier on, but I was actually before I decided to become a neurosurgeon, I was heading to become a hemotologist. And that was actually just an interest carried over. When I was a resident, I did a review of DVT prophylaxis and management in neurosurgery patients across the board. I was looking at trauma, looking at spinal cord injury. There are some things that have not changed a lot since that was published. And that’s back in the early 90s. I worked with Bill Gallay, who’s an internist, and does a lot of work with the clinical research. We did a meta analysis of DVT prophylaxis, looking specifically at chemical DVT prophylaxis and elective brain craniotomy with blood and brain surgery. So patients coming for tumors, for electric procedures, just to try and get a clean cohort. When I look at it, when we finished that, it became obvious that there were a couple of things that stood out. One is that if you use chemical prophylaxis in these patients, there’s an increased risk of bleeding. And that’s not surprising. I mean, you look at even the literature on aspirin for prophylaxis of vascular events, and people who’ve never had a vascular injury, but it goes to large population studies, there’s an incidence of hemorrhage that’s a little higher, even with aspirin in that group. When we looked at this, we looked at complications. Specifically, we’re going to look at those issues in relationship to that also restricted benefits and try and do a risk benefit ratio. And I think there is a risk but there is also a real benefit. We emphasize the need for when possible use pneumatics, intermittent pneumatic compression. And those I think are effective if people actually wear them. In the ICU, that’s a little easier to enforce. I’ve done audits in the neurosurgical ICU and found up to 30% non-compliance. And I’m sure there are days where it’s even worse than that. So again, as we all know, they only work if they’re on the patient and functional. There is an interesting little paper buried in an obscure journal. But it was from the Salt Lake City experience with DVT prophylaxis and neurosurgery patients craniotomy on patients undergoing craniotomies. And one of the things they identified was that low molecular weight heparins seemed to have a higher risk of hemorrhage. And the reason why that’s a big issue was that the consequences I think, as we’d all agree with hemorrhage, intracranial hemorrhage, from the point of view of neurological function and outcome can be quite devastating. And try to limit that. They thought if there was an increased risk of all heparins that was not that significant a risk with a low dose heparin, so unfractionated heparin. So I actually had gone through a phase where I was giving low dose heparin before like the craniotomies , and then carrying it on. It generates a fair amount of things when you have people undergoing craniotomies who are on chemical prophylaxis at the time of their surgery. So I stopped doing that. I don’t think the evidence was that overwhelming that it was beneficial. But I’m quite willing to start people on prophylaxis with unfractionated heparin very quickly, recognizing that unfractionated heparin carries the risk of HIT, although it’s not very high. So, the Salt Lake City protocol and what I try to advocate is that we do stockings, pneumatic stockings and metabolic progression, we start unfractionated heparin, either that night or the next morning, and then at 72 hours, we’ll switch into low molecular weight heparin if they are not mobile. And so if a person’s mobile four hours a day, they don’t need to go on chemical prophylaxis. Now, the trauma patients are going to be not mobile, so you have to consider that. So I usually will take that approach. That said, I think you’re going to find incredible variability wherever you practice regarding this particular issue, and there’s not going to be a real consensus because nobody’s really done the studies properly. When we did this systematic meta analysis on elective cranial surgery. There were a couple of studies that have been done in cranial patients comparing normal heparin to unfractionated, heparin, and the bleeding risks, although not statistically significant, we’re definitely higher. And one of the trials has actually stopped. And they were definitely higher in that and the low grade heparin. There was a study that was done when I was, in the early 90s, I was a PI in Calgary for a Spinal Cord Injury Trial using low molecular weight heparin. It had to be stopped because of the increased risk of epidural hematoma, spinal epidural hematomas. And the neurological consequences of that. And that paper was eventually published quite a long time after the study was stopped, but it demonstrated the risks in that acute phase. If I had to give a recommendation, I would say pneumatics. If the patient is stable the next day, I think, personally, I think they can start on unfractionated heparin within, you know, less than 24 hours, you know, 18 to 24 hours and then if you’re going to start low molecular weight heparin, if they’ve had hemorrhage issues, usually rescan them and then we would start them on low molecular weight heparin. The one proviso is that if they have a drain in place, an EVD, if there’s any risk that that’s going to have to be removed or replaced, those agents are going to have to be stopped with sufficient time to allow any potential risk.
Ameer Farooq 59:23
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