Hello, welcome back to part two of local anesthetic pharmacology. Now I'm going to talk about the clinical application of these medications for obstetrics. Same disclosure statement, I have no disclosures. Here are the learning objectives. You have access to these through the slide set. When we talk about dosing guidelines, I'm always a bit hesitant. When I lecture, I inevitably have two or three people come up to me afterwards and say, how do you do whatever? So I'm doing a C-section, how do you do a spinal for that? I'm doing a total knee, how do you do a spinal for that? And I'm really hesitant to give out recipes. And the reason is because I can do three total knees in a day and do three very different anesthetics, even though it's the same procedure, it's the same surgeon. Each of these patients is different and we really need to tailor our techniques and the way we manage these things to each individual patient and each individual situation. And in obstetrics in particular, that can be very different. So patients are different, the situations are different, the urgency is different. And so I'm very hesitant to give recipes. Having said that, I will do some, but I need you to also take into account my clinical practice. What I'm giving you are recipes based off of what I do in clinical practice. And my clinical practice is likely different than yours. So I'm in private practice, I'm in a rural setting, it's a community setting. We have no learners. We do have SRNAs, so we have nursing and seizure students, but we have no other learners in the operating room. And so, again, things tend to move fairly quickly. Our surgeons are very skilled and I don't have to worry about a medical student coming in and closing a surgical incision. So keep that in mind as I talk about the application of these drugs in the clinical situations that we're going to talk about. So I'm going to go back and review some of these local anesthetics. I mentioned that we do use 2-chloroprocaine. I use 2-chloroprocaine quite a bit in my clinical practice. Not so much in OB, but a lot in the operating room. 2-chloroprocaine has a bad reputation on the street and that's because when they first introduced it, and actually first and second time that they introduced 2-chloroprocaine into clinical practice, they had preservatives in it. The first preservative, sodium bisulfite, is both neuro and myotoxic. Well that makes sense. I don't know why you would introduce a local anesthetic that you know we're going to inject around nerves and then put a preservative in it that's neurotoxic. I mean it doesn't take a rocket scientist to figure out that that's a bad idea. So they pulled it from the market after some bad outcomes. They reintroduced it with EDTA as a preservative. For those of you that are familiar with EDTA, it's the clear liquid that's in the bottom of the light blue coagulation tubes. It binds calcium, so it prevents the coagulation cascade in anywhere that calcium is in the coagulation cascade, and that's how come the blood doesn't clot in the tube. And again, it doesn't take a rocket scientist to figure out that if you put something that binds calcium into a local anesthetic, and we inject large volumes of local anesthetic into the epidural space, and it leaks out a little bit into the paraspinous muscles or the erector spinae muscles, and starts binding the calcium, these patients would have horrific back pain, so much so that they would beg you to take the epidural out because the back pain was worse than the labor pain. And so again, it doesn't take a rocket scientist to figure out that that's a bad idea too. So they finally got smart and just came out with a preservative-free brand of 2-chloroprocaine. So Nesacane 2-chloroprocaine, this is the 2%, they also have 3%. This is isobaric, and you can see here it's EDTA-free and it's methylparaben-free. So this is preservative-free. It says for epidural, you know, nerve block, all that stuff. It will say not for spinal anesthesia on it. It's okay, you can use it for a spinal anesthetic. We know that that's fine. That was all related to the use of the preservatives in it. In addition to that, all of these local anesthetics were never intended to be used in spinals, although they're perfectly fine to do spinals with. And because they're off patent and they're generic, nobody's going to spend the billions with a B of dollars to do phase three clinical trials to get an FDA indication for spinal anesthesia. So they just leave it knowing that full well that we do use it. It is preservative-free, you can use about 40 or 50, 60 milligrams in a subarachnoid block. I do it all the time for our orthopedic surgeon who does a knee scope in about 20 minutes. It'll last 40 minutes. It's a perfect anesthetic for those types of procedures. Doesn't have a lot of cross pollination, so to speak, with obstetrics except for one particular application. I'll talk about that in a second. So it's 2% or 3%, I mentioned it's isobaric. It's the fastest on you can set up and start operating almost within five minutes, usually about eight is what I say. And so that's really nice. However, it's a very short duration. It's not much more than 45 minutes. I mean, you hit 46 minutes and the patient's already starting to wiggle. And if they're still suturing, they're going to feel it. You've got some issues. It's also very short in the epidural space, probably about the same, probably about 45 minutes in the epidural space. But who cares, right? You just redose. Now, if I do use it in the epidural space, and I'm getting to that point where I need to redose it, I'm not redosing with two chloroprotein. I'm going to redose with a different medication, something that's a little bit longer acting. And my go-to is ropivacaine. I'm going to use rope in here when I redose. So with an epidural, duration doesn't matter. We don't really care. Why? Because we have access to the epidural space. We can simply inject more drug. So here's some dosing guidelines. For a subarachnoid block, absolutely you can use it. I typically use the 3% because I can use 45 milligrams. It's one and a half mils. But if I use the 2%, I'll do two mils, it's 40 milligrams. It gives me about a TA block for about 45 minutes. Now, this is not enough for a C-section. So again, for obstetrics, just put a big X here. You're not going to use this in the subarachnoid space for obstetrics because you can't really push it high enough because it's isobaric and you don't have the duration that you need. Even in my practice at 45 minutes, we're probably still putting this, 45 minutes from when I inject, we're probably still suturing the skin at this point. And so you have a very unhappy patient, you have a very unhappy surgeon as they try to chase the patient around the room to finish the procedure. Now you can use it in the epidural. Typically I'm using the 2% because it's a little bit less massive drug. You do have to be careful with toxicity. I am very judicious about this, three to five mils at a time. Repeat them every five minutes. Probably in a crunch, if it's really a crash section, I would say you could do this every three minutes because again, the onset is five minutes, at eight minutes it's set up. So every three minutes you'll be able to see where you're headed. There is one caveat that you have to worry about, and that is that intrathecal or, put a slash here and put epidural, opioids will not work once you use 2-chloroprocaine. I don't know why, nobody really knows why. But it's true, they won't work. And so if that is part of your plan, 2-chloroprocaine is really going to derail that. I don't think it's as big a deal anymore. Before 10, 15 years ago, we didn't have an option. Now we have an option. So what do we do? I typically use 2-chloroprocaine and then I'll just put bilateral tap blocks in the PACU. So we can augment with tap blocks. I will talk one more time about 2-chloroprocaine when we actually talk about the surgical procedure part. Right now what I'm talking about is the drugs themselves. And then I'm going to talk about the application of these drugs in particular situations or surgical procedures. As I mentioned in part one, the lidocaine family, there's actually two parts of the or two different AMI groups. There's the lidocaine family. Really the only one that we use in the lidocaine family is lidocaine. Lidocaine really doesn't have a place in obstetrics other than in our test dose. Lidocaine is hydrolyzed by the P450 system. The mepivacaine family is de-alkylated by the P450 system. I don't think that makes any big difference, but there is slightly different metabolic pathway. And so now you know more than most. Again, mepivacaine, probably not going to use in obstetrics. Absolutely going to use bupivacaine and ropivacaine and ropivacaine is my drug of choice. I'm not going to worry for infusions because of that safety profile that I talked about in part one. Let's talk about these drugs individually. This was lidocaine when I first started clinical practice. This is what was in 99% of all spinal trays in the United States, as well as a little bottle of epi. So we would put a little epi wash in with our lidocaine and we would get 90 minutes out of this. It was fantastic. It was the gold standard. It worked really, really well. Unfortunately, we had some bad neurologic outcomes related to this. It's probably related to concentration, boricity, because this is hyperbaric, and then stretch in high risk patients. So that's kind of that two hit phenomenon. I'm not going to spend a lot of time talking about it. This isn't in clinical practice anymore, so you don't have to worry about it. It is still the gold standard. I would say that nobody's using it in subarachnoid blocks anymore. I don't think there's really any indication for using lidocaine in a subarachnoid block. And if you do use it, even if you use the 2% isobaric, you're just asking for trouble. Because if there is anything bad that happens, you really have nothing to stand on. You can use it in peripheral nerve blocks. I'll explain why I don't. You can use epinephrine. I talked about using an epinephrine wash and that will definitely extend the duration of that local anesthetic. So for guidelines, again, I don't think you should use it in the subarachnoid space. People talk about using the 2%. It's usually isobaric. The 40 to 60 milligrams will give you nine minutes and it is absolutely associated with transient neurologic syndromes. And because of that, I don't think you should use it. I think you should switch to mipivacaine. Mipivacaine is a far safer drug. Essentially, it is the same thing as lidocaine. You dose it exactly the same as lidocaine, but you don't have the risk of this with mipivacaine. You can use it in the epidural as your primary anesthetic. The one time that I would suggest that it would be appropriate to use is in this particular situation. And that is if you have a true crash C-section, an emergent cesarean section in a patient that has a working epidural and you don't have access to 2-chloroprocaine. If you use 2% lidocaine and you add the bicarb to it, it is almost as fast as the 2-chloroprocaine and you can get to where you need to get quickly enough that you can get the procedure started and get the baby out and then continue to dose until mom is comfortable, particularly when they externalize the uterus. Unlike 2-chloroprocaine, you can use opioids in the epidural space afterwards. So that's kind of nice. I think most people are not doing that anymore. I think most people are moving to tap blocks for postoperative analgesia and we can talk about that at the workshop. So I think that's really the only application for lidocaine in current obstetric clinical practice. Bupivacaine is the workhorse. This is what's in 99% of all spinal trades now. We have the 0.75% hyperbaric bupivacaine. This is the workhorse. I think most people use this all the time. I think most people, particularly for orthopedics, and I know we're not talking about orthopedics, but most people for orthopedics will just use all two mils. I think that's a shame, but we can talk a little bit about dosing and I will talk a little bit about how I dose this in the obstetric world. This is the isobaric stuff. This is the 0.5% isobaric. Again, this is preservative free. It says preservative free. It does say not for spinal anesthesia. Everybody uses it for spinal anesthesia. You can and indeed will use this for spinal anesthesia. I use it all of the time in my clinical practice. Not so much for obstetrics, a lot for orthopedics. Some for obstetrics because as you know, during the pandemic, we lost our supply chain, particularly once the hurricane hit Puerto Rico and we lost all of our pharmaceutical supply from Puerto Rico, which included IV fluids and it included bupivacaine. We had to switch to this because that's all we had available. We talked about that. So here's the first time now we have to start asking ourselves, is this my primary anesthetic or am I using it for analgesia? In addition to that, am I using this for a spinal or am I using this for an epidural? Because I will tell you I can dose bupivacaine for an intrathecal for analgesia and I can dose spinal bupivacaine for anesthesia for a caesarean section. Same is true for an epidural. I can push this for a caesarean section, I can push it up to T4, or I can use a very weak concentration and use it for analgesia. So that again, now the discussion that you have to have with yourself is what's my primary goal, what's my primary outcome? And then based off of that, we can make some cogent decisions for the clinical application. Now if we're talking about a spinal, I'm almost always going to use hyperbaric because I just get the better kinetic with it. And again, for a C-section, here's my kind of go-tos, 12 mg. I almost always use preservative-free morphine, I use 150 mics, 0.15 mg, whatever you want to call it. I know a lot of people are moving away from using the opioids, I think it still works really really well. I'm old school, I've been doing this a long time, I have a lot of experience with it. Our surgeons are fine letting us do it. Unless there's a contraindication and I'm doing a spinal, I'm going to be in their CSF anyway, I just go ahead and do it. I think it's a better alternative. Having said that, we are moving a little bit away from that. There are times when we don't put the morphine in there, and in those cases, then I will do bilateral tap blocks and PACU after the baby's been delivered. Again, if we're doing an epidural and we're using anesthesia, we're going to use 0.5%. If I'm doing an epidural and it doesn't matter whether it's anesthesia or analgesia, I am typically not using bupivacaine, as I mentioned in the toxicity lecture, I am almost always going to ropivacaine at this point. I just think it's a safer drug to use, it's a better drug to use, you get better sensory motor separation, it's just there are lots of different reasons why you should be using ropivacaine in your clinical practice, and that is indeed what we use in our clinical practice. All of our epidurals are ropivacaine epidurals in obstetrics. If you're going to use it as analgesia, then we're using very low concentrations, 0.125% or 0.065%. If you're down here, you have to add an opioid. You need the synergy of the opioid at these concentrations, otherwise you're not going to get an effect. I actually prefer hydromorphone, I think five mics per mil of hydromorphone is a better mix with bupivacaine, particularly at these lower concentrations. You get a little bit better spread with hydromorphone than you do with fentanyl. Fentanyl, it's so lipophilic, it sticks right where it's at. You don't get enough spread. So I actually prefer hydromorphone. I lost this battle in our clinical facility because we could only have one. We use these stupid cassettes in the pump and they would only pre-stock one type of cassette on OB, so we actually use fentanyl. So we use 0.2% ropivacaine with two mics per mil of fentanyl. We've moved completely away from bupivacaine as an infusion on obstetrics. Here's ropivacaine. It's my go-to drug for infusions. When I'm using it for epidural, again, as an anesthetic, we can use 0.5%. For an analgesic, you can use 0.2%. You can use 0.1%, but again, if you're using 0.1%, you have to have an opioid. With 0.2%, you can run plain, and there are occasions we see some opioid-addicted moms coming in on suboxone and those kinds of things, so we'll run these plain and then we'll give them IV opioids to supplement to meet their needs and their demands. We typically don't like to deliver those kinds of patients in our facility because, again, we don't have a great nursery, and we end up having to transfer those babies. Those babies come out addicted, and there's a whole skill set in managing those babies in their first couple of weeks of life in order to wean them from the opioids, and that's a real skill set that we don't particularly have in our facility. Now, I'm going to talk about how do I do spinals for a surgical procedure. What are we talking about? We're talking about C-section. Now, there are three different types of C-sections that we do in our clinical practice. You may have more. I don't know of them, but this is what I see in my clinical practice. That is, we have scheduled sections, there are urgent sections, and then there are truly emergent or crash C-sections. These are very, very rare. Thankfully, these are very, very rare. I've probably done three of these in the last five or six years. Urgent is fairly frequent. We see non-reassuring fetal heart tones, or there is non-reassuring fetal well-being, I guess is the newest vogue term, and so we're going to the OR. Yeah, it's urgent. We need to get this baby delivered, but it's not like taking 10 minutes is going to make a difference in outcomes. Versus scheduled, we see a lot of scheduled. We no longer do VBACs or TOLACs, so we don't do vaginal birth after delivery, or we don't do a trial of labor after C-section, which is a TOLAC. We used to do that, but we're in a community. We're simply not set up for that. It's too risky, and so we've stopped doing that. Thank God, but those are definitely something that you need to be very aware of. We see a lot of breech presentations, so we'll have scheduled ones for those, so anybody that has a prior C-section, we will deliver by C-section. Anybody that's breech, obviously, we'll deliver by C-section, and twins, occasionally, we'll let them deliver in our facility, but there's got to be a good reason why, and then we're typically scheduling those as well. Now, the next question you have to ask, so how much time do you have? Next thing is, do you have a working epidural? Because if you have a working epidural, then use it. If not, then we're talking about doing a subarachnoid block. Now, this is kind of an interesting thing. So when I'm on OB, I cover OB for 24 hours. I'm the only anesthesia provider, so if I put an epidural in, I know whether it's working or not. So I put it in, and the patient's really comfortable. I don't have to re-dose them. They're really saline. Now, we're coming for an urgent C-section. I know that epidural's working really well. I'll dose up the epidural. Conversely, if I put an epidural in, and I'm going up every 90 minutes to re-dose them, they're having a lot of breakthrough pain, we know we're going to end up going to C-section because of that. That's a kind of pathonomic of a bad labor pattern, and that increasing in pain is often enough to kind of tip the scales in that direction, and in those cases where I'm not confident that the epidural's going to work perfectly, what I do is I bring them down in the operating room, I sit them up, I pull the epidural out, and I do a single-shot spinal because I know it's going to work. So that's kind of where I'm talking about when I'm talking about a working epidural. And then also, do you have a cooperative patient? Is the patient going to tolerate you doing all of this kind of stuff? Ultimately, the question comes down, how much time do you have? Is this scheduled? Is this urgent? Or is this truly emergent and truly a crash? So if it's scheduled, you have all the time you need. Take it. Bring them into the room. Get them nice and comfortable. Sit them up. Get them in great position. Do a subarachnoid block. And what do I use? I use somewhere between 1.4 to 1.6 mils, or 10.5 to 12.5 milligrams of the hyperbaric bupivacaine. As I said, I typically do put preservative-free morphine in. I'm probably one of the last holdouts, but again, my hair is gray. I've been doing this a long time. This works really well in my hands, and the patients do very well with it. If we don't use the morphine, again, you can do tap blocks post-operatively in the PACU. Those work very well, too. And I will do tap blocks. I'll actually do a... Even if they have breakthrough pain and they've got preservative-free morphine in there, I'll still do a tap block. There's no contraindication to that, so go ahead and do that. One of the caveats that I'll do, and this has actually nothing to do with local anesthetic pharmacology, but it's relatively new if you're not aware of this, absolutely need to add this to your practice. I do this religiously now, and that is about 10 minutes before I'm going into the room. I give them four milligrams of Adanatron IV. We don't know why this works, but it works really well. You just don't see the big swings in blood pressure. They don't get nearly as hypotensive from the sympathectomy when you place your block, if you've done that, and it works very well. Now if it's urgent, this is where you start to have to know a lot. You have to know about your OB and what they're willing to tolerate and how much time they're going to give you. You have to know how much time you have, right? Is this one kind of D cell, or are these a couple of variables? It's getting late, and the OB wants to go home and sleep rather than stay here all night and watch variables. I mean, that's a very different situation where we've got repeated late D cells, right? That's still urgent. It's not emergent. It's still urgent, but that's kind of the higher end of urgent, and so how much time are they really going to give you? Again, if this is urgent and I've got 10 minutes, I'm going to sit them up. I'm going to stick a needle in their back. I'm going to do my standard dosing because in 10 minutes, they're going to be ready. They're going to be able to do the surgical procedure. I'm going to get a great block. I know it's going to work really well, and that's what I do even in an urgent situation. Now if it's emergent, this is where it really gets kind of touchy. You really have to really know yourself. You have to know how good you are. You have to know how much time you have. How long is it going to take you to get mom from where she is now onto the table and how much time is it going to take them to get ready to cut? Because that's going to give you the idea of how much time you have. You may want to consider using 2% 2-chloroprocaine. You can do it in a subarachnoid block. You just have to be careful. You have to know you're obese. I don't think this is a great idea. I put it here. I give it to you as a consideration. I know some people will do it. I'm not a fan. In a true emergent crash C-section, this is what I do. I bring them into the room. I get them on the table. I get left uterine displacement. I get everything set up. I get a good mass seal, tidal ventilation of 100% oxygen. While they're prepping, draping, surgeon in the room, knife in hand, everybody's looking at you. And then you tell mom, take four big deep breaths as you give propofol sucks. You do an RSI. And once you see the tube go through the cords, I look up and I say, go. And by the time I'm finished taping the tube, the baby's usually out. So this is really in a true emergent situation. I don't have an epidural. I've got to do a spinal. I seriously consider this as my first choice. I'm not a big fan of this. This takes too long to set up. You can't get started in time. And that's why I think you could use two chloropocaine, but you have to be really careful. Remember, you only have about 40 minutes and the patient's going to be really uncomfortable at the end of 40 minutes and they're still trying to suture the uterus closed. Then what are you going to do? Now you're going to have to convert to a general in a really unfortunate situation, in an unprepared situation. So in these cases, I don't think this is an option. I don't think this is an option. I think this is truly the best option. And I have done three general anesthetics in about the last five years for truly emergent cesarean sections. And I, and personally, and again, this is just Franklin talking. This is my clinical practice personally. I think that is the right choice. And that's it. I didn't talk about how to manage epidurals. I talked a little bit about what we do. And the reason is the epidural dosing is, as I mentioned, it's just enough volume to get them comfortable. So we'll talk a lot about that. Chuck does a beautiful lecture on dosing epidurals and breakthrough pain for obstetrics. And he'll do that at the workshop. And so because of that, I'm going to defer to Chuck and his discussion. In addition to that, you'll have plenty of opportunity to have small group discussions with each of the faculty during the hands-on portion of the workshop. So with that, I will wrap up this part of the discussion. Here are the references, as I mentioned. And it's been a pleasure, and thank you for your time.

obstetric anesthesia

local anesthetics

C-sections

epidurals

bupivacaine

postoperative pain management