Okay, so in this presentation, we're going to look at regional and general anesthesia considerations specifically focusing on the cesarean delivery timeframe. My name is Tom Mingus, and we're going to get started. So I have no disclosures, I have no financial relationships or any commercial vested interest in any of the content that we're going to discuss. Also I will not be talking about any off-label use during my presentation. The learner objectives are very simple. We're going to discuss the anesthetic considerations for cesarean delivery, utilizing both neuraxial and general anesthesia. So let's talk about the neuraxial approaches. So when it comes to cesarean delivery, the most common approach that is going to be utilized is going to be an intrathecal block or a spinal or subarachnoid block. There are some advantages to a spinal. Ultimately, it's a very fast onset. You use a very low volume of local anesthetic. Their success rate is relatively high. You get CSF, you administer the medication, the majority of time you're going to have a successful spinal. Now there are going to be some considerations on failures, and we'll talk about those, but ultimately their success rate is relatively high. It's a relatively simple technique. While there is some dexterity that's involved in it, there's not a lot of extra steps that need to be done when considering that versus something like a CSC or an epidural. The position is very heavily determined by the boricity of the medications, commonly spinal. Markane is going to be hyperbaric. So we as anesthesia providers can really manipulate the height of the block relatively easily with the head of the bed or either Trendelenburg or reverse Trendelenburg, basically. Density really is determined by dose. We can get different concentrations of medication to get similar results based on the fact of the volume that is given, but ultimately we can give a little bit higher concentration of medication and get very profound dermatonal innervation just with that small volume. Now the disadvantage really comes into play is that it's a single shot. You put the medication in and depending on the patient's ability to metabolize the medication, the ability of the patient to keep the medication in the subarachnoid space really determines how long the block will last. Typically blocks last between 60 and 120 minutes, but again, the inclusion of certain medications really will play a heavy role in how dense the block is at what dermatome for how long. We also need to discuss epidural. Epidurals are commonly used for C-section, specifically going to be epidurals of a laboring patient that are now converted to a surgical anesthetic. The advantage is that if the epidural is well placed and it has been highly functional, you have a catheter in place and you can actually titrate the volume up at a relatively slower rate. So a maternal patient that has cardiac dysfunction that we don't want to give a massive dense block to immediately or very quickly, an epidural has that advantage is that we can give the medication in incremental doses and get to the level that we want without potentially overshooting. Also when you have that catheter in place, if the surgery continues on or there's been a complication and they need to do additional work, you're able to extend the length of your block because you still have access to the epidural space to administer more medication. Now the disadvantage is also in that because it's in the epidural space, you do have to give a higher volume in order for it to be successful. So instead of doing that one or two mLs, we now are giving between 15 and 20 mLs. So the likelihood of that, if that catheter has migrated and now we have an intravascular catheter, the likelihood of potentially having a complication from that does rise because you're giving much larger volumes. The other disadvantage that can be seen as an advantage, but also a disadvantage is that if you have a mom that is going back quickly for a C-section, because it takes time for the medications to diffuse to their site of action, it is a little bit of a slower onset, which can be an advantage for a maternal patient that has cardiac dysfunction, but can also be a disadvantage in the setting of establishing a dense block that has a high level very quickly. And then the other disadvantage is that if the epidural has been in place for a long period of time or the pain control has been marginal, there is a, or we've been re-dosing the epidural multiple times, there is a likelihood that when we try to convert from a labral analgesic type epidural to a surgical anesthetic type epidural, they will not, it will not be adequate for surgery itself. So then there is a technique that is kind of a combination of both. It's called a combined spinal epidural and they abbreviated CSE. The advantages are that you do get that spinal density, if that's what you choose, and then you have the epidural in place that you can prolong the block. Also if the spinal does not function, or for some reason it never sets up the way we think it should set up, if the epidural is in place, we can salvage the block utilizing the epidural as the alternative method helping prevent the patient from having to go under generally a seizure for the C-section. The other advantage is that some of our patients that have denser ligaments or have farther distances or you don't get a great feel because the ligaments are much more stretched out and not as dense, having that bigger needle of the TUI in place gives you a little bit better feel of the changes in those levels as we get closer to the epidural and intrathecal space. So the fact of the matter is that sometimes the small introducer and small spinal needle of the spinal kit itself is just not good enough to get to where we need to go. So a CSE is one of those things that we can do to help our cells be more effective in placing neuroaxial anesthesia. The other consideration is that we don't have to always give spinal local anesthetic. You can give an opioid in the intrathecal space and then use your epidural to dose up the local anesthetic at a slower rate helping decrease the profound sympathectomy. Now some of the disadvantages is it really comes down to it takes longer to set up potentially from a standpoint of the kit. You have to assemble the kit. Most facilities you have to either assemble the kit or add things to an epidural kit in order to have the full setup. It's two techniques basically. You do an epidural, then you do a spinal, then you thread the catheter. So it takes longer potentially. Now in a practiced hand it can be relatively quick, but the plain simple fact is there are more steps to do with CSE. Also the fact of the matter is that if the spinal is successful, you can't really know for sure if your epidural is going to work or not. So just based on you have a dense spinal and you thread the epidural catheter, does the epidural catheter mean that it's in the right spot? The answer is going to be no. So that can be seen as a disadvantage also is that you really don't understand if it is going to be functional until your patient needs it and then potentially it's not going to be functional. So as we go through this I also add some studies that I found ultimately looking at the plain simple fact of like if spinal versus CSE or whatever we're talking about. So when you look at the literature on this is that ultimately literature says that both are good things and the ultimate thing is that we can deliver opioids into that intrathecal space which helps pain control for the maternal patient in the long term. There is no real clear difference between like neonatal outcomes between CSE and spinal so that is definitely advantageous for us. But ultimately you know really the question is what is the outcome and the outcomes seem to be very similar between epidural and spinal. So when it comes to some of our considerations remember when we look at our CSE versus our epidural the answer is that the CSE because we're given a spinal we can get much denser block much quicker versus our epidural which is a little bit slower. The likelihood of motor block really does have some play in it being that if we've given a spinal dose the patient will get a profound motor block very quickly and since if we've given a full dose spinal dose you are probably going to get some hypotension. So when you look at literature again epidural does have a little bit less hypotensive outcome but ultimately if both are functional you can achieve the same result. The one consideration is that if you do a CSE you know that and you get CSF back you know that more than likely you're midline so the picture helps describe that because the intrathecal space is contained towards the center of the epidural space if we are getting CSF and we get a spinal block and then we thread our epidural captor ideally we know that we're in the midline of the epidural space meaning that our likelihood of us getting a unilateral block is decreased. So when you look at catheter failure rates between CSE and epidural we know that since we aren't 100% sure on a standard epidural if we are always midline you can see that there is some failure rate differences between epidural and CSE and this is where the idea of a dural puncture, epidural comes into play is that we in a dural puncture instead of us administering volume into the spinal space we are now just confirming that we're midline by getting CSF back. So let's talk about some dosing. When it comes to spinal dosing we know that the majority of medications that we give currently right now are going to be 0.5% or 0.75% bupivacaine. The thing about the 0.5% it's an isobaric solution while the 0.75% is combined with dextrose which makes it hyperbaric meaning that it will sink in relationship to the CSF so your block will tend to drop lower depending on where gravity is so wherever gravity is block is going to go. Commonly for a spinal dose is going to be in that 12 mg range and for 0.75% that's going to be 1.6 ml of volume. Also when it comes to spinal dosing commonly we include opioids in that, opioids being a short term pain control which would be fentanyl and then a longer term pain control like morphine. Both are effective at pain control, fentanyl being short term, morphine being a little bit longer term and the key though is anything that we put in any of these spaces need to be preservative free so there is morphine that does have preservatives in it so if you're going to use a longer acting morphine or Dilaudid make sure that it is preservative free so morphine is usually classified either astromorph or duramorph designated that being preservative free. The other consideration when it comes to our morphine is that because it's a longer term opioid it can stick around and as a result our maternal patients or anyone that's received duramorph or Dilaudid intrathecally does have a higher risk for prolonged or longer term risk for prolonged or latent or respiratory depression that is seen later in the patient's immediate recovery period rather than fentanyl being an early respiratory depressant. Then we can also add epinephrine, epinephrine is going to be one of those things that it helps prolong the block by decreasing the uptake so ultimately in a spinal it's going to be a small volume of our concentrated epinephrine so 100 mics or 0.1 ml is usually where the volume that is given but again it's one of those things, all these things can be given or you can select certain things to you can either choose to have only opioid, you can choose to have only local antiseptic, this is where you know commonly it depends on what you want from the spinal but for a c-section the ideal thing would be have a dense local antiseptic block and then addition of opioid and then understanding that we can prolong our block utilizing epinephrine now not everywhere does that if you know that your OBs are relatively quick then most places omit epi but in a place like where I work at a large academic medical center we place epi on most patients just to ensure that our block lasts long enough when it comes to converting labor epidurals to surgical epidurals this is really where understanding if your epidural is functional is key if the epidural has not functional then conversion to a surgical anesthetic really becomes extremely challenging and a lot of times as a result the epidural will fail and when we say fail that just means that it might have somewhat of a block but it is not dense enough for the patient to tolerate surgical interventions being being cut open for a c-section so commonly when you convert a labor epidural to a surgical anesthetic you needed to use a large volume of a high percent local anesthetic and that could be either local lidocaine local 2% or 3-2 chloroprocaine so either of those can be used there are some caveats when it comes to chloroprocaine mainly being the ability to use duromorph is decreased and also the rapid onset also is followed by a rapid off off set of the local anesthetic effects so that means you need to redose earlier so commonly lidocaine 2% is going to be one of those things that is given and it's given in divided doses and then you can titrate up the level of the block now like we discussed it is a little bit of a slower onset when it's plain lidocaine so you can add things like bicarb but there's a national shortage of bicarb but ultimately you add bicarb helps change the pka and allow for a little bit quicker onset and then you can also add epinephrine to this block also helping prolong the block and ideally the reason that we would do that is to help in case the epidural would get pulled from its current position during a quick over to the bed you've gotten on at least a good amount of block and that hopefully it'll last if if you're a surgeon or your obstetric provider is relatively quick the other considerations is really when is it going to be an adequate function. Epidural is really how have you been managing the patient during the labor timeframe. So we're very concerned about converting an epidural, especially in the setting when there's been a significant amount of breakthrough pain. So I went to literature and looked at like, where is the, what should we use as a cutoff? And ultimately what literature says is that if you've given one or two doses for a breakthrough pain, usually that can indicate that you will be okay to convert. But once you start getting over that two range of dosing, the likelihood that the epidural conversion is unsuccessful starts to rise exponentially. Other things that help determine if the epidural is going to be converted successfully is going to be in the setting of either a CSE or a DP. An OB provider, anesthesia provider was the one that placed it. So was it the placement done by a skilled provider? Also, if the C-section is not at a very stat or emergent classification, the ability for us to understand will this epidural work in a slower timeframe is going to be much more evident. So from our standpoint, if we recognize that this is not going to set up well, potentially we can give additional volume or we can actually convert to a CSE and give a low dose spinal. And then again, give extra local in the epidural space to kind of prolong the block if need be. Other thing, the interesting thing is as our patients get taller, they actually have a higher risk of having a failed epidural. So literature has described if a patient is over that 66 inch mark, then they will actually have a higher risk to have a failed epidural, which I thought was interesting. And then interestingly, choreo is going to be one of those things that some of our patients have present with after being ruptured for longer periods of time. And knowing that choreo changes membrane potentials, changes membrane permeability and changes the pH of our patient really does have some link to is our epidural medications going to be as effective? And the answer is going to be, if choreo is present, the likelihood of an epidural failing does increase. So let's talk about some other neuraxial considerations. One of the things that we really need to understand is this idea of a failed spinal. So when it comes to a failed spinal, we really need to understand where does the majority of failed spinals come from? Ultimately, what literature has found and what anecdotally I have found in my practice is the fact that spinals usually fail when the needle, the lumen of the needle, so majority of our spinal needles have a lumen that is on top. So we use a pencil point. So you have the lumen that is not at the tip and the lumen is not all the way into the intrathecal space and that results in either two things happening. Either the local partially goes into the intrathecal space like the top picture and then partially into the epidural space or we dissect that dura and so we get a subdural block rather than intrathecal block or interestingly, this valve effect on the second picture being right here, ultimately showing that when there's positive pressure pushing into the spinal needle, so we make the initial puncture, we do get flow but then when we do our injection, our positive pressure actually causes it to valve and push the dura towards the intrathecal space and our medication is then injected into the epidural space so then we don't establish a block because the volume is so low or like I said, this dissection idea comes into play where we dissect the actual dura itself. So really ultimately, the way to avoid this is to methodically ensure that not only do you have flow, so you see that drip, drip, drip but you also do an aspiration, you see swirl because of the boricity change between the dextrose and the CSF and continued flow so aspirating a little bit extra to ensure that you have adequate flow and you've added some negative pressure to it in order to get that, to see if that membrane gets sucked into the lumen of the needle. So really, why would we get flow and then we don't get flow? It really has to come down to patient movement and inadvertent needle movement. So the patient moves minuscule amounts that we don't even perceive or we move minuscule amounts that we don't perceive and while we got flow, then we injected and then it was in an epidural space or a subdural type of response. So understanding that a majority of the time if we have a failed spilence, an us problem. Other things to consider would be how would we identify, we don't get a great block, we don't get a onset that we characteristically see and the patient feels a positive out. So before they start, all patients should be tested to ensure that they have proper dermatome. Other things to consider is sometimes the medication can be exposed to heat and it really, from that standpoint, that can actually cause a failed epidural or a failed spinal. It is in the space, everything was right but the medication's chemical characteristics were actually changed. So if we identify that the spinal has not set up appropriately, then best thing would be either to reattempt the block in a CSE type fashion so we reduce the dose of the spinal medication to ensure that we don't get a high level block and then use our epidural to supplement towards the end. And then if it's an emergency procedure or the patient refuses to do another interaxial technique, then general anesthesia will be the way that needs to be done. So if you have an epidural that has not converted well, what can you do? Well, you can do an epidural, redo the epidural. You can do a CSE and do a reduced dose of our spinal and then have the epidural there for potentially prolonging the block or you could do a spinal. Each one carries its own risk. If we redo an epidural and we give the same volume, our patients, especially a smaller BMI patient is gonna be at a higher risk for having less symptoms. A CSE is kind of the mid ground between a spinal and an epidural because if we just do a straight spinal, we give the same volume, our standard volume, the likelihood that they have a high spinal increases in literature up to 50%. So now we have to reduce dose the spinal and then we don't have a long enough block period. So CSE really is the kind of the middle ground where we can give a small dose of spinal marcaine to help get this block that we want and then you have the epidural for afterwards. So other things to consider. So some things that really play into these spinal and epidurals are gonna be hypotension. So knowing that our neuroaxial techniques have a high level of hypotension, so we have to be prepared to treat that. So utilization of things like ephedrine, neozofran fluid and extremity compression all have been utilized within literature to promote the decrease in neuroaxial hypotension, ultimately knowing that as our maternal blood pressure decreases, the risk for fetal compromise increases. So any of these things are supported through literature. Other things. So we talk about fluid loading. So fluid loading is a little bit of a controversy about the timing, but ultimately the goal would be to be getting some volume expansion during the placement and immediately following the placement to help maintain the fluid, the preload back to the maternal heart, knowing that we're gonna have a sympathetic response. So if the answer is, do you give it way before, do you give it during, knowing that the crystalloid will eventually leave the intravascular space, colloiding has really been one of those things that is a good idea to just give them during the actual placement, knowing that giving it too early really has no benefit because the fluid has left the intravascular space. Interestingly, colloid versus crystalloid, there is no difference. So that's why crystalloid is the preferred method at that point. So let's talk about some general anesthetic considerations when it comes to cesian section. There are some risks inherent to general anesthesia. And as we deal with a pregnant patient that has a chance for more challenging airway, increased risk for aspiration, increased risk for aspiration, and there's a neonate that's present, the likelihood that you're gonna have an outcome that is not as favorable rises with the maternal patient. So this is why majority of providers will want to do a neuraxial technique, knowing that maternal population has a higher risk when it comes to general anesthesia. When you look at general anesthesia for cesian section, though, sometimes it's really the only option. And so you have to do it. And that could be that there is some massive reason that they can't have a neuraxial technique. And sometimes that would be the maternal refusal of a technique that is a neuraxial. So again, remember that intra-awareness is gonna be higher in the pregnant patient. They're gonna utilize a MAC that is a little bit higher. The question is, is there fetal compromise? And the answer is, it really is a timing-dependent concept. So if the fetus is removed quickly, the exposure to the involvable anesthetic and the propofol is less. The question is, if we have a delayed birth, or we, for some reason, weren't able to get a fetus out quickly, then the neonate has been exposed to large volumes of involvable anesthetic and to induction agent, and they can be depressed. So this is where having a provider that can make sure that this neonate has a supported airway immediately post-op or post-delivery is extremely important. But ultimately, knowing that the induction dose may decrease, but ultimately, there is no, if the baby, a fetus is removed quickly, there is no real significant umbilical pH measurement changes compared to this to a noraxial technique. So some things that we really need to consider as anesthesia providers, like there's gonna be times where we have to do an emergency GA. So I just placed a workflow. The biggest thing really comes to being prepared and then having a good communication with the surgical team because we don't want to induce too early because we wanna decrease the fetus's overall exposure to our general anesthetic agents. So majority of time, we'll get the patient in the OR, be completely ready, have draped, prepped everything, and then communicate, are we ready to go? Yes, place the patient in general anesthesia, avoiding things like fentanyl IV. So this would be where you use a lidocaine, a paralytic agent, and your propofol to get them to sleep really quick. And then once you have the tube through the cords and you've made sure that you can ventilate the patient, communicating go, go, go, whatever has been the agreed upon verbiage, but ultimately getting them to sleep quickly and getting baby out is gonna be the key here. And then because they are an aspiration risk, really making sure that they're awake before you extubate them so they can protect their airway because they are still at a high aspiration risk at this point. Other things to consider are gonna be when it comes to our C-section, our neuraxial techniques, it's gonna be nausea and vomiting. I went through literature to try to find what is the best way to avoid it? And the answer is there is no one solid way to prevent nausea in the pregnant patient during this timeframe, during C-section. There's been a lot of different examinations of our common anti-emetics, our medications that deal with pressure, so using neo-infusions, all of these things have some benefit, but there is no end-all be-all. So utilizing a combination of these really is what literature kind of points to is that there's no one agent that is better than the other, just utilizing a combination will help decrease the overall nausea incidence. Now, anecdotally, I found that rapid administration of decadron and our azithromax and exteriorization of the uterus, BOVI, the sense, and oxygen administration all increase nausea. That's an anecdotal observation, but ultimately trying to prevent nausea is one of the more challenging parts of doing a C-section under neuroaxial anesthesia. When it comes to oxygen administration, commonly we administer oxygen to our patients, hoping that it will help the fetus stay a little bit higher oxygenated, but literature does not support that. There are, I looked at a Cochran review that said there is no real significant difference between MOMSET and PO2 and umbilical artery saturation. It was not clinically significant, so that's interesting, kind of a difference of what we would think. What they ultimately conclude is if the mom needs oxygen at baseline, then this is the best time to use oxygen. When we look at our other complications or other considerations when it comes to C-sections are gonna be preeclampsia. When it comes down to it, when you look at general anesthesia and rates of stroke, ultimately pre-E does have a stroke incidence, especially when it comes to our general anesthetics, but just know that we need to be very cognizant that our patients that have preeclampsia that receive general anesthesia do have a little bit higher risk for stroke as a risk factor. When it comes to our airway, airway is gonna be one of those big complications that we're very concerned about with our pregnant patient. Their airway is a little bit smaller. Their airway, as a result, it's a little bit more difficult, so really understand that assessment is gonna be key, and if we feel like we're gonna have trouble, then being prepared for that is gonna be very key, and meaning that you need to utilize video assist and then also potentially having a fiber optic and potentially utilizing an LMA, which is a very last minute type thing or less than ideal thing, but ultimately we need to keep the mom oxygenated in order to keep fetus oxygenated, so really consider if you have a patient that has a high level lesion or has a very challenging airway or has history of it, we need to take extra care and really make sure that our neuroaxial anesthesia is first adequate and it doesn't progress too high because this, again, could present an emergent situation. Some things to consider, though, when it comes to our patients is that these mothers are going to be at risk for aspiration basically due to their motility being slow and then potentially, if it's an emergency type situation, having large meal or having something in their belly is gonna be one of those things that can be there, and then potentially us multiple attempts having a traumatized airway are all reasons to have high likelihood of having a difficult airway. And here are my references. Thank you very much, look forward to seeing you guys in person.

anesthesia

cesarean delivery

neuraxial techniques

spinal block

epidural

general anesthesia

maternal factors