Local Anesthesia in Pediatric Dentistry: Dr. Malamed Explains the Risks of Overdose

You're listening to The Dr. Phil Klein Dental Podcast Welcome to the show. I'm Dr. Phil Klein. Pain prevention is an essential aspect of all dental treatment. And although local anesthetics represent the safest and most effective drugs in all of medicine for managing and preventing pain, pediatric patients are at increased risk of serious complications when receiving local anesthetic for dental care. Today we'll be discussing the safety of local anesthetics and management of systemic complications in the pediatric patient population. Our guest is Dr. Stanley Malamed, a dentist anesthesiologist and emeritus professor of dentistry at the Herman Astro School of Dentistry of USC, formerly the University of Southern California School of Dentistry. Before we get started, I would like to mention that Dr. Malamed’s webinar titled Safe Local Anesthetic Management in the Pediatric Dental Patient is now available as an on-demand webinar on VivaLearning.com. Simply type in the search field Malamed, M-A-L-A-M-E-D, and you'll see the webinar. It's an excellent presentation for the entire dental team. Viva Learning would also like to thank our sponsor, Health First. Health First supports thousands of dental offices with emergency medical kits, medications, and devices that help dental practices manage medical emergencies. So thank you, Health First, for your continued support for Viva Learning CE initiatives. Dr. Malamed, it's a pleasure to have you on Dental Talk. Phil, pleasure to be here, as always. So tell us about the MRD. Tell us about the maximum recommended dose and how it applies. to local anesthetic and the pediatric patient? Sure. It's really important for every dentist and hygienist to know how much they're injecting into a patient. And this is true for adults and as well as pediatric patients, more critical for the younger patient who weighs less. In our webinar, we talked about the most common drug-related emergency that occurs from local anesthetics, and it occurs in children. And it's overdose of local anesthetic. And it occurs most often when a general dentist is treating children, not a pediatric dentist, because pediatric dentists understand that children, they don't weigh as much as adults. And it is always possible with any drug, but we're talking about local anesthetics here specifically, to give too much. So the maximum recommended dose is a number established by the Food and Drug Administration, the FDA in this country, a number above which you should not administer a local anesthetic. So let's just talk about that for a minute. So, for example, for lidocaine, the MRD in the United States is 7 milligrams per kilogram. And I'm going to use kilograms and not pounds because we are probably the only country in the world that still insists on working with pounds as opposed to kilograms. So for lidocaine and arcticane, it's 7 milligrams per kilo, okay? So let's say that this child weighs, I'll say 55 pounds, which is 25 kilograms. So 25 kilograms times 7, 7 milligrams per kilo for lidocaine, is 175 milligrams maximum. That's a lot. Now, if you consider there are 36 milligrams in a cartridge of lidocaine, we're talking about five cartridges maximum. Okay. And the way MRDs are calculated, it's a matter of, they're saying 175 milligrams of lidocaine to that patient at one time. Okay. And which again makes no sense because to give five cartridges of a local anesthetic to a child at one time to any patient, well, no, no, let's go back to children, to a child would be, I'm going to say it crazy. OK, but it's a number above which the benefit of using a drug is now being outweighed by the risk of using a drug. There's no guarantee that if you approach or exceed the MRD, something bad is going to happen. There's no guarantee of that. There's also no guarantee that if you are below that MRD, something bad won't happen because everybody's different. The MRD is again, it's essentially. defined as a point at which the negative begins to outweigh the positive of a drug that's being administered. So that's what this is all about. It's not a guarantee that something bad is going to happen, but you don't want to exceed that number. Again, what we want to do when it comes to local anesthetic with any patient, again, a child especially, is to administer the smallest dose of the drug that will provide us with the effect of pain control. And we rarely, if ever, need to get to the MRD. You know, many of us, when they think about how much, when they're dealing with local anesthetic, they say no more than four cartridges. You know, they don't get into the details of the seven milligrams per kilo, 36 milligrams per cartridge. As an endodontist, 15 years of practice, I rarely gave more than three cartridges. Now, I'm not counting intrapulpals, right? This doesn't count intrapulpal injections, correct? Sure. Right. Intrapulpal would not really count in that discussion because intrapulpal, first of all, it hurts like hell, but it works. I mean, it's like the last resort, isn't it, when you're dealing with a hot tooth. And most of that local anesthetic is not being absorbed into the patient's cardiovascular system. It's essentially just staying inside that root canal, the pulp chamber, and we can discount that. It really doesn't count toward the maximum recommended dose. Right. So what is the major drug -related complication associated with local anesthetic administration? I'm alluding to it is overdose. There's a new name for local anesthetic overdose in the literature. It's probably been there for about five or 10 years. They now call it local anesthetic systemic toxicity, or the acronym is L-A-S-T, LAST. Allergy, which some people always bring up, is a non-factor, an absolute non-factor. when it comes to the local anesthetics that we're using in our dental profession today. But it is an overdose of local anesthetic, again, specifically when dealing with the younger, lighter weight child in a general dentistry office. You mentioned that we're not talking about pediatric specialists, but when any healthcare provider administers local anesthetic to a child, even if it's one cartridge, can't that cause a problem if aspiration isn't? done properly where it's directly injected into the vessel, even if it's one cartridge? Oh, absolutely. I mean, any local anesthetic injected into, it'll be a vein most likely because it's almost impossible to accidentally inject into an artery, but into a vein. One cartridge of lidocaine, artacaine, mepivacaine, prilocaine, bupivacaine injected rapidly intravenously guaranteed will produce a rather severe overdose reaction, which is a seizure occurring almost immediately. Now that is one of the two most common causes of overdose. It is not the most common cause, but yes, that's why aspiration prior to every injection that we give in dentistry is critically important for safety. So those MRD stats that you talked about apply to giving it into the local tissue, being absorbed by the capillaries after it already took effect. As a nerve block, correct? Right. MRD basically is saying that you're injecting the drug properly, okay? You aspirate it, you inject it slowly, not into a blood vessel. It's the total amount of local anesthetic, the number of milligrams that you're giving that is critically important here. If you're giving the drug directly into a blood vessel, you may be putting in 36 milligrams of lidocaine, but you're putting it directly into the cardiovascular system. As I said a moment ago, you're going to see Basically, an immediate onset, literally within seconds of a really intense seizure. What do you think is happening more in practice, iatrogenically, too many milligrams of actual lidocaine or arcticaine or whatever they're using, or improper aspiration where it's going into a vessel, a vein? By far, the most common cause of an overdose last reaction is giving too much. I've been involved. I started teaching in 1973. It's now 2022. And because of my books or whatever, I get involved in a lot of these legal cases as an expert witness. And I do defense 99% of the time. I've been involved over these years in 27 cases where a child who weighs less than 30 kilos, which is 66 pounds, has died. has suffered from permanent brain injury from getting too much local anesthetic and that that's from giving too many cartridges too many cartridges too many milligrams done properly but simply putting in too much now let me just there's a scenario i want to go through this with you okay so it starts out with a young under 30 kilos 66 pounds a young lightweight child well-behaved who is in need of extensive dental treatment. We're talking if the child has 20 primary teeth, 15 of them need something done. They have a lot of caries. So maybe it's stainless steel crowns, pulpotomies, whatever. A lot of work to be done. And because the parent is insisting, usually it's a younger dentist. This dentist is trying to build their dental practice. They need patients. So the doctor was trained in dental school that you only treat one quadrant at a time on this young child. But because of the parents' insistence and because the dentist wants to be a good guy or good gal, okay, we can do the entire thing at one time. So the first mistake that this doctor made was treatment plan. I have never met a pediatric dentist anywhere in the world, and I mean this as a fact. When I bring up... know, the case I'm just talking about, you know, 15 teeth on a kid who weighs 25 kilos. I asked the pediatric dentist in the audience, how many cartridges of local anesthetic are you going to use to anesthetize the entire mouth? And the answer I've gotten, and I swear to you this is true, I won't do it. Pediatric dentists won't do it. They'll do it in two visits. They'll do it in four visits, but they will not treat. under local anesthesia alone in their dental office, that patient in four quadrants at one time. Now, if we put this, if the child is a screamer, a yeller, handicapped, and we put them in the operating room, we will do the entire procedure at one time because the risk of general anesthesia outweighs the risk of local, but they won't do it. So the first mistake is the treatment plan. Now, the next mistake this doctor makes is he or she picks a very good local anesthetic. 3% mepivacaine. Mepivacaine is carbocaine, polocaine, isocaine, scandinous. It has no vasoconstrictor, which means all local anesthetics without epinephrine are basically vasodilators. They increase the blood flow. So the doctor picks a very good drug, but uses it improperly. He's using it in four quadrants. The next mistake this doctor makes, and this is the one that really boggles my mind, is they inject all four quadrants at one time. Rather than doing a quadrant, before they finish it, inject the next quadrant. Before they finish it, inject the third quadrant. They give four quadrants at one time, which is crazy. Okay, now the next mistake the general dentist makes is they inject the child as though he or she were an adult, which means they give the full content of the cartridge. They give all 1.8. With adults, there's rarely a need to give the entire content of the cartridge. Okay, except maybe for the mandibular block. But in a child, never. There's no rational reason for this. If you go to a pediatric dentistry office and you see you have a young child in the chair and you see one empty cartridge on that tray, they've given two, three, or four injections with it. But that's why these problems don't happen in pediatric dental offices. So we have the wrong treatment plan. We have a good drug being used for the wrong reason. We have all the drugs being given at one time, multiple injections, and full cartridges. And those four things add up. The patient's numb. The doctor gave the injections properly. As the doctor starts the treatment, what's happening in the background. is the blood level of the anesthetic is steadily increasing. And about 10 minutes into the dental procedure, the overdose occurs and the patient starts seizing. So that's exactly how this happens. Again, 27 cases of overdose over the years. Essentially, every one of them, that was a scenario for it. So let's say the doctor decides to use Mepivacaine, which doesn't have a vasoconstrictor. How does that affect the MRD? Okay. Well, that MRD is based, again, on the drug. So, it's 6.6. For mepivacaine, it's 6.6 milligrams per kilo. And let's say if the child weighs, let's make it 20 kilos to make it easy to do the mathematics. That is 132 milligrams of the drug. Okay. And there are 54 milligrams of mepivacaine in a 3% cartridge. So, we're talking about two and a half cartridges as a maximum dose. Now, again, a pediatric dentist. if they wanted to, probably could anesthetize that entire mouth with two and a half cartridges. It's not that hard to do. Remember, kids are small. The bone they have is a lot thinner than adults. So in the mandible, they can do an infiltration. And the nerve that you're aiming for is a lot thinner in a child than an adult. So the volume of anesthetic... is a lot lower in that situation. If they used a local anesthetic which contained a vasoconstrictor, none of this would happen. Because what epinephrine does is it keeps the drug in the nerve longer, which produces a longer duration and a deeper anesthetic. Those are the two things a doctor likes about epinephrine. But the third thing epinephrine does to a local anesthetic, which you don't see, is it makes it safer. And it makes it safer by keeping the drug inside the nerve longer. It gets out of the nerve more slowly, and the blood level of the anesthetic is lower. And that's really the most important factor, the one that is unseen, safety of adding epinephrine. Now, let's go back to Mepivacaine for a moment, okay? Because Mepivacaine plain is a great drug. Again, but if you start using it in younger children in multiple quadrants and putting in full cartridges, the risk of getting an overly high blood level and getting into local anesthetic systemic toxicity. What is the effect of hypercarbia on the seizure threshold of a local anesthetic? Okay, so during a seizure, and this is actually true even if it's an epileptic patient, but we're talking about local anesthetic overdose right now. The seizure will stop. What happens is when the blood level in the brain... exceeds what is called its seizure threshold. You can think of this if anybody in the audience imbibes alcohol. There is a level of blood alcohol above which you're legally intoxicated. If you're driving a car, you'd be DUI. Consider that an overdose of local. Okay, so we give a local anesthetic, we exceed that level, the seizure occurs. Now, the same way when you drink alcohol, the buzz goes away after a while, it's because the drug, the alcohol, is leaving the brain and going to other places in the body. It's called redistribution. That's the way a drug stops working. So the patient will have their seizure as long as the blood level in the brain remains high enough. And about a minute after the seizure starts, as blood is still circulating in the brain, blood level now falls below that seizure threshold and the seizure is over. However, In the post-seizure phase, if the airway is not being maintained, we're talking about simply doing head tilt chinlet, part of your CPR. If the patient is not getting enough oxygen in, if they're not getting rid of carbon dioxide, having too much CO2 is called hypercarbia. That lowers the seizure threshold. So it takes less local anesthetic to produce a seizure. And what that leads to is, unfortunately, in the absence of maintaining an airway and in the presence of hypercarbia, a second seizure occurs. A second seizure occurs, which is usually more violent and longer lasting than the first one. And it's all because of the treatment of that seizure was inadequate. And again, the treatment of the post-seizure phase is simple. It's simply lift the chin, maintain an airway. So hypercarbia is absolutely not good following a seizure. So in the event a young child has a seizure in the chair, is it absolutely necessary to call emergency medical team when that happens? Or can they do what you just suggested and see if it could just diffuse and get redistributed where the seizure stops? So I would say, first of all, if this patient doesn't have a history of epilepsy, which we're assuming they don't, and as a seizure... following a local anesthetic administration yes absolutely guaranteed every time 9-1-1 the first thing you do of course is you stop the dental treatment and you maintain an airway head tilt chin lift but in at that time somebody else in your office is making that telephone call for 9-1-1 absolutely every time because they're going to come to the office the seizure should have been finished by that time But they want to evaluate that patient. They may even take him to the hospital for evaluation to make certain that nothing, no brain damage or probably brain damage as a GERD. So yes, you absolutely want to call 911 in that situation. And if a patient has a history of having a seizure, how does that GP handle that patient next time? Okay, so here would be the difference. So let me just talk about this patient who is epileptic, child epileptic. And let's forget about local anesthetic overdose-driven. The child is in the chair, and even perhaps before the dentist gave the patient the injection of local, they had a seizure. We know the kid is epileptic. Now, there's a parent out there or a grandparent. Somebody brought the patient to the office. That person knows the kid is epileptic, has probably seen them have a seizure before. So you call the parent in or the guardian in, and you ask them. shall I call 911? Okay, now they may say to you, doc, this is just one of his normal seizures, in which case there may not be a reason to call 911. But if the parent walks in and says, doc, call an ambulance, don't even ask anything, just make the phone call. Now, on top of that, regardless of what that parent says, don't call 911. If you, the doctor, are uncomfortable with what's going on, you make that phone call. It's your decision to make. Now, let's go back and talk about what you just said. A patient with epilepsy who has an overdose related to local anesthetic. I mean, the answer, I think, is pretty obvious. You make that phone call for 911. In both cases with seizures, of course, you know, during the seizure, while they're having the seizure, you simply prevent them from being injured. You gently hold on to them. Don't let them fall from the chair. But it's once the seizure is over, in both cases, you want to maintain an airway. It's more critical with the local anesthetic overdose because we're talking about hypercarbia and local anesthetic blood levels. But again, maintaining an airway in the post-seizure phase, be it an epileptic patient or a patient having a local anesthetic overdose is very, very important. Is there any way for the GP to treat the patient who is not epileptic that comes back for another procedure but has a history of having a seizure prior in the office, most likely due to... of local anesthetic. I would doubt very much if that parent would bring a child back to that office again. But let's say they did, because you are the best pediatric dentist in, or the only pediatric dentist in that town or city, maybe. I would hope that if that ever happened in your office, you would have learned a lesson. You would have said, I dodged a bullet. Okay, something bad happened probably because of the fact that I gave too much local anesthetic. And I have to learn how to do it right. Okay. I mean, that's what I would think. Again, I really, if I were a parent of a child that had a seizure in a dental office produced by local anesthetic overdose, I ain't going back there. I'm going to find a pediatric dentist for my child. Okay. If I'm that dentist, I'm saying to myself, I dodged a bullet and I got to learn how to do this right. So let's talk about Articane. Articane is a 4% epi solution. Right. It has a little bit more rapid elimination. And some doctors find that to be safer than lidocaine. I don't know if you agree or not. You can tell us if you agree. Can artacaine be administered to patients under four years of age? Firstly, I taught for 40 years at USC School of Dentistry and I retired in 2013 from teaching. We got artacaine in the U.S. in the year 2000. Now, I taught local. And a student would ask me, Dr. Malamed, what is the best or what is your favorite local anesthetic? I would never tell him because I don't want to bias you. I want them to use them all and figure out for themselves which drug they like. Now that I'm retired, it's articaine. There are so many things about articaine that are superior to any other local anesthetic. And we usually, lidocaine is the gold standard. You know, it's the drug to which all new locals are compared. And we compared arcticane to lidocaine in our studies back in 1997. Our studies were interesting because they did not show that arcticane was more effective than lidocaine. They did not show that arcticane worked faster than lidocaine. Yet if you ask a dentist, do you like arcticane? Yes, they do. Why? It works faster. It works better. I don't miss as often. Hard to numb patients or easier to numb with arcticane. Okay, that is anecdotal evidence. Science did not show that until the endodontist, your specialty, the endodontist started using it. And Al Reeder from, I hate even saying it, The Ohio State University, he and his residents have published quite literally hundreds of research papers on local anesthetics over the years. And they started using articaine in adults by mandibular infiltration in the mandible. And I got to work. And there are studies now. is showing that if you inject a full cartridge of articaine in an adult maxilla, 82% of the time, you will get palatal soft tissue anesthesia. So, I mean, we're finding out there are a lot of advantages of articaine. Now, let's go back to the pediatric population. You said that it's gotten rid of a little bit faster. No, it's not. It's gotten rid of a lot faster. The amount of time, if we take a blood level of a local anesthetic, lidocaine, for example. We call this the elimination half-life of the drug. The blood level decreases by 50% for lidocaine, epivacaine, and prilocaine in 90 minutes. And we say that the drug is gone from your body in six times the half-life, which is nine hours, 540 minutes. Articane's half-life is 27 minutes. Not 90, 27. It's gone from your body in 162 minutes, which is two hours and 42 minutes. So again, one cartridge of any local anesthetic. Let's go back to the main subject here. One cartridge of any local anesthetic, including arcticane, given intravenously rapidly, will produce an overdose. But again, the most common cause of last is putting in too much. Putting it in properly, but putting in too much. That scenario with arcticane is unlikely to produce last. Because once arcticane leaves that patient's nerve, enters into capillaries and veins it's being metabolized significantly more rapidly than any of the local anesthetic yeah which means that it's not going to really have the same profound effect on the brain and the heart as lidocaine would after it gets into the circulatory system absolutely it's gotten rid of a lot faster yes it and from that perspective it's a safer local anesthetic Yes. Interesting. It did get a bad rap, though, at one time, right? There was something with arcticane that gave it a bad rap. Yeah. And happily, well, the bad rap was 4% anesthetics, arcticane, given by mandibular block, have a higher risk of producing paresthesia. Right. That's what it was. And that is a bad rap because it's not true. And if anybody who is listening to this podcast, I give you my email address, okay? They can contact me. So it's my last name, Malamud. at usc.edu and i have published a good number of articles debunking debunking that that paresthesia controversy if you will okay the bottom line is you know again when i practiced endodontics i i don't think maybe twice in 15 years i used more than three cartridges Maybe twice. So three, and that was my cutoff. Just anecdotally, it was three. I wasn't absolutely doing the math on the number of milligrams, seven milligrams per kilo, 36 milligrams of the cartridge. I just said, if I have to go more than three, I'm doing something wrong if I can't get this patient numb. And then I would go to intrapopal. And you can use water. You could use water in a syringe for intrapopal. It's pressure and necrosis. Yeah. It's the pressure. It's the pressure that does it. Yeah. So from the safety perspective, three was my cutoff. And again, as I said, maybe twice I went to four. And that was because I was probably doing multiple root canals in different quadrants on the same patient that had, you know, they had to have it done for a lot of reasons. But again, I gave them anesthetic after I finished the first molar. I did a number two. And then if I moved to number 14, I was giving another injection. you know, an hour later after instrumentation of the first one. Right. So I certainly wouldn't load the patient up with a loading dose of that. So, but given that scenario, it's very unlikely that the LAST would be the cause of a seizure. The cause, if I had a seizure in the office, would be lack of good technique regarding aspirating prior to injecting. Right. And, you know, you would realize that for two reasons. Number one, the overdose would occur instantaneously. I mean, I'm not exaggerating. We're talking about to get that drug from injection site to the brain will take literally under 10 seconds. So you will have that seizure starting, boom, just like that. And the other thing, and this makes no sense given what I just said about a seizure, the patient won't get numb because you're not putting local anesthetic in the tissue. which would be an irrelevancy considering the fact that they're having a seizure at that same moment. Yeah, that's not going to be a major concern at that point. Like I mentioned in my introduction to the audience, and we get thousands and thousands of dental professionals that listen to this podcast every week, please check out Dr. Malamed’s webinar on Viva Learning. It's really phenomenal. It'll save a life. Hopefully, it will never have to save a life, but it could potentially save a life in your practice if you... to this one-hour presentation. All you got to do is go to vivalearning.com, type in Malamud, M-A-L-A-M-E-D, and you'll find it. And again, we want to thank our sponsor, Health First, for all they do for their support for continuing dental education. Thank you so much. Thank you, Dr. Malamed. Thank you very much. Thank you.