Neuraxial Ultrasound and Spinal Anesthesia for Cesarean Delivery

CHAPTER 1

So we're gonna run through doing a neuraxial ultrasound. So the first thing you can do is you can put the probe horizontal. And what you're doing in this position is to look for... So this is the problem, we're not getting... Okay, there. So you're looking for a pagoda sign. So this is the sacrum. It gives you a very distinct angle. We're just gonna go... So once you feel you've seen the sacrum, we're gonna start counting up the interspaces. So this hyperechoic line over there is the sacrum. You can see I'm going down. So I'm following the sacrum down. And then as we follow the sacrum down, we get to the first interspace. So this would be L5-S1 interspace. This is the ligamentum flavum, and over here is the vertebral body and the other side of the dura. And then we're gonna use this to count up. So that's the next interspace. You can see the lamina here, and there's vertebral body, next vertebral body, and then we've got the lamina of each interspace. So we're gonna count up to the next interspace over here. And this would be viewed as L3-4. At that point, you would slide your probe across like this to get into the center. And then we get a very characteristic bat's ears. So there is your vertebral body, posterior vertebral body. These little bat's ears on either side, and I'll try and even them out. She's got a little bit of scoliosis, so we're just trying to angle the probe there. There's one over there and one over there. These are your articular processes that give you an acoustic shadow. And this over here is where you would get your ligaments of flava dura. This is the spinal canal, the darkness inside there, and that's the vertebral body of dura. So if we were going to then mark off our interspace, we would put a measurement tool over here, and the distance to interspace over there would be 4.2 centimeters. And that's as easy as that, it is. At that point, we would mark it off, which would be a combination of marking this side and marking the interspace there. We wanna make sure the image is centered as possible, so we can do that. And then when these two get joined on this side this is L3-4. These two lines would join right over there, and that would be the interspace that we go into. And as I mentioned for her we can feel the spinous process fairly well, but she had a little bit of a scoliosis to her back. So the advantage with using ultrasound in this setting is we've been able to work out that that needle would need to be angled slightly off to the right to be able to get the optimal space. So just to run through it again you can do this to firstly determine the pagoda sign over there, which is the sacrum. You don't necessarily have to do it. You can start just going parasagittal, oblique angle. You can see the probe is going vertical, but angled in to try and get the interspace, and there's a very clear sacrum. So you slide up in the sacrum, and then you get into the first interspace which would be L5-S1. And then you keep the vertebral bodies in position, you keep moving up along there. Sorry, I'm just sliding off there. Very clear interspace over there. Interestingly, if you want to, this is L4-5 space, you can measure the distance into there. And the distance over there, and you get a similar-ish space over there. I'm gonna slide up to the next interspace, which is over there. And then we can move it over there, and that gets your next interspace. So you can measure in both different angles, but that's the way we go. So this is the interspace we're now going to mark off for our spinal. Okay, so that's it.

CHAPTER 2

So we're gonna demonstrate a spinal here. So initially we do a very thorough cleaning of the patient's back. We've preprocedurally marked out the correct interspace that we're gonna be going into L3-4. And we will walk you through a typical spinal that we do at our institution. Going by the kit setup, the medication we use, and how we go and do the spinal. So we're doing this procedure before a cesarean delivery. So what we do with the procedure is to try and minimize spinal hypertension. And we do this with providing a coload of one liter of crystalloid, which we start when we start doing the spinal immediately. We give it under pressure from a pressure bag, and then we run a phenylephrine infusion started at 0.5 mics per kilogram per minute. So this is the kit that we use. There's standardized kits that we like. We start off with using some local anesthetic, which we administer with a very small-gauge, 31-gauge spinal local infiltration needle. Our dose for our C-section is 1.6 mL of 0.75% bupivacaine. We generally overdraw, and then we remove the air bubbles and make sure we accurately give 1.6. We do not like to reduce our dose. We view comfort during cesarean as priority. We can easily manage spinal hypertension with the coload and the phenylephrine infusion. We then add two drugs to it. So this is fentanyl. Fentanyl is for intraoperative analgesia. We do 15 micrograms of fentanyl. This provides about an hour and a half of analgesia. It's mainly for intraoperative analgesia and reducing intraoperative nausea. And then we add for postoperative analgesia, we add morphine. This is just a very small dose, 100 micrograms of morphine. At our institution, we let patients select either a low dose, medium, or high dose. This is our standard 100-microgram dose. So it's all comixed in a syringe. Because we use such a small-gauge spinal needle, a 25-gauge spinal needle, we have an introducer as part of the kit to help direct the needle. All right. So the back is prepped. We use chlorhexidine solution with a tracer, that's why it's purple colored. We allow it to dry for two minutes. So while we're preparing the kit, we have it dried out, and it's ready to go. We use a sterile cover to make sure the back is kept nice and clean. With this we're very careful to not desterilize ourself and what we like about this clear drape is that we are able to see the full back rather than just a little pocket hole that the opaque drapes don't allow. So now I'm gonna ask you to take the position, put your chin down, shoulders down. One, two, three, take a deep breath. It's lidocaine, and we're very generous with giving a nice local infiltration. You can see a nice local spread so that you get good anesthesia throughout the interspace if we need to move it. Now you're gonna feel some pressure in your back. Try to put your chin down and round your back as much as possible. Perfect. So we like to always be in contact with the patient, you can see the left hand is in contact with the patient. We slowly advance the needle in a steady fashion, feeling for the first pop and then the second pop. So we're straight into the CSF, you can see there the CSF, we allow it to come all the way out to make sure there's no air in. A little twist to get the nice connection so there's no leakage. You see no air entrained and no fluid dripping out as we inject. We like to inject at a steady speed, not too fast and not too slow. And so that's on the perfect speed. We'll just aspirate at the end. So we aspirate at the beginning and the end, we do not aspirate in the middle 'cause we wanna minimize movement to the needle, and then they all come out. And it's as simple as that. So a combination of neuraxial ultrasound measurements along with a single shot spinal for cesarean delivery.

CHAPTER 3

It's at this point that we will continue to coload and we'll start the phenylephrine infusion. I want you to move a little bit more to your right. Perfect. And then we're gonna tilt you over. It's gonna feel really weird. Don't try help me, okay? We're quite big proponents of a left uterine displacement, and we do that by putting a little wrapped towel under the cushion of the bed and then we should be good to go. And now it's regular blood pressures every minute to make sure we detect any hypertension early. We aim at keeping the blood pressure as close to normal as possible. So that's our aim at this point in time. We're not gonna let it move. We also look very closely at the heart rate. If the heart rate increases, we anticipate that that's an increased cardiac output and therefore we need to be ready to treat a drop in blood pressure because of SVR reduction. If you wanna see our coload set up, so what we do is we use a pressure bag to allow us to give fluid as quickly as possible. We're essentially now almost finished this fluid, and then we run our phenylephrine infusion over here at .5 mics per kilogram per minute.