Background:
Neuraxial anesthesia comes in two forms, spinal and epidural (can also have a combined spinal/epidural). For labor and delivery you will most likely only have a spinal anesthetic if you are going to have a cesarean section. Of course there are exceptions to every rule and there is an exception to this rule as well. Some anesthesiologists will place a low dose spinal if you ask for an epidural for labor.
Some anesthesiologists perform spinals when they place an epidural for labor in order to deliver quick pain relief. The reason I choose to not do this is because I like to know my labor epidural is working. If I place a spinal anesthetic and then I thread in an epidural catheter, I won't be able to know if my epidural catheter is working, here is why. The spinal that I placed prior to threading the epidural will make the patient comfortable. I rely on dosing my epidural and then having a comfortable patient 15 minutes later to verify that I have a working epidural, if the patient is already comfortable from a spinal I have placed, I cannot dose my epidural and have verification of correct placement because the patient is already comfortable.
You may be wondering, what is the difference between an epidural and a spinal, or is there any difference? The difference is based on anatomy and location. An epidural is above the dura. Eli- meaning on top of, and dura meaning tough ligament. So an epidural is a space on top of the ligament. A spinal, also know as intrathecal, is below the dura, or below the ligament. The dura is a tough ligament thats main function is to hold the cerebrospinal fluid; similar to a balloon that holds water. The cerebrospinal fluid in the dura is used to protect the brain and the spinal cord. So an epidural is above the dura and a spinal is below the dura.
The Procedure:
Start by obtaining the consent from the patient, letting them know the risks and the benefits. The benefits are obvious, pain relief. There is belief that decreasing the amount of pain will decrease the catecholamine response, which in turn will increase uteroplacental perfusion. Most spinals in obstetrics are done for cesarean sections. However, like I stated previously, some anesthesiologists will used a combined spinal/epidural technique for labor and delivery. Back to the main point, spinals are done for cesarean sections (c/s) because numerous studies have confirmed a spinal or an epidural technique is safer than a general anesthetic for c/s. An epidural would be used in a c/s if a mother is laboring and during the course of labor is administered an epidural and subsequently is taken to the operating room (o/r) for a c/s. An epidural is sometimes used in patients who have had numerous previous c/s or are morbidly obese. The reason being, an epidural allows the anesthetist to length the neuraxial anesthetic because a catheter is left in place when you do an epidural and commonly is not for a spinal anesthetic. The side effects are multiple. The main ones being hypotension. The hypotension has a cascade effect and can lead to nausea/vomiting and fetal decelerations if not treated quickly. The less common side effects are high spinal, when the anesthetic is too high, it may be hard for the mother to breath or she may not be able to breath at all, in which case the spinal is switched to a general anesthetic and we breath for the mom. Seizures and death being the other rare side effects of a spinal anesthetic. Another fairly rare side effect is a spinal headache. Spinal headaches have almost been entirely eliminated. Through research on the issue, we have been able to substantially decrease the occurrence of post spinal headaches. What we have learned is to use smaller needles and a needle with a pencil point tip.
We also will perform a history and a physical exam. The basis of the history is to ensure you are appropriate candidate for a spinal anesthetic, there are no bleeding disorders, neurologic disorders, or any cardiac valve abnormalities that may make us reconsider using a spinal as our anesthetic. Parturients typically have lab results, I will look at these results to ensure they are normal. We will also ask about the course of your pregnancy to ensure no serious issues are surrounding the course of your pregnancy, such as pregnancy induced hypertension, cardiomyopathy of pregnancy, placenta accreta, etc.
Next the anesthesiologist will prepare the spinal tray, seen in the picture above. Also we begin to prep the mothers back to sterilize the skin surface as much as possible.
Once the prep is done, the time out is done, the anesthesiologist has wash their hands and they are set up, they will begin the spinal procedure.
We start by infiltrating your skin with 1% lidocaine, which is in the bottle on the left. This allows us to advance larger needles later on in the procedure without causing as much discomfort. We allow the lidocaine to take effect and then we go onto the next part of the procedure. For a spinal anesthetic we typically use the L3-L4 interspace to decrease the risk of injecting our solution into the spinal cord. A
To get to the spinal space, the anesthesiologist needs to put the spinal needle through multiple layers, the skin, adipose layer below the skin, interspinous ligament, ligamentum flavum, the epidural space, and then the dura, and then into the cerebrospinal fluid. Confirmation that one has reached the spinal space is the presence of cerebrospinal fluid (CSF) in the spinal needle hub.
The spinal needle is in the above picture. The spinal needle in the above picture is the blue hubbed longer needle. When you reach the spinal space you will see CSF in the hub of the blue spinal needle. The hub is the blue portion of the needle. There is a stylet that goes into the center of the needle. The stylet is a thinner needle that delivers more strength and integrity to the spinal needle and also prevents tissue from clogging the spinal needle as the spinal needle is advanced through skin, fat, and ligament. If there were tissue in the core of the spinal needle then one would not be able to confirm proper placement of the spinal needle in the CSF as the tissue would prevent CSF from traveling into the core of the spinal needle and into the hub.
Once CSF is seen in the hub of the spinal needle the local anesthetic that will be used is injected in the spinal needle. I typically use 0.75% bupivacaine with dextrose mixed with fentanyl and morphine. There are a number of mixtures that anesthesiologists use, it is similar to a recipe, each has its own merits. I use bupivacaine, a local anesthetic, for the pain relief, the loss of motor (so you cannot move your legs while the operation is in progress), and its lack of painful aftereffects. I mix the local anesthetic with fentanyl for its quick action and synergistic action with bupivacaine. I add morphine because it lasts for 24 hours, offering you pain control once the operation is over. However, adding narcotics is not without deleterious effects. Nausea, vomiting, pruritus are all potential side effects of adding narcotics to the spinal mix.
Post spinal anesthetic:
Like I have stated previously, I never use a spinal anesthestic for laboring patients. So, I will briefly touch on the experience of a c/s from the anesthetic standpoint, after administering a spinal.
After a spinal, unless contraindicated, I will typically administer a vasopressor, which will maintain the blood pressure. I have had good success with this approach in decreasing the number of hypotensive patients, thereby decreasing the number of patients retching after the spinal.
When the baby is being delivered, you will feel them pushing, as they will be pushing in the substernal area. This is uncomfortable. Throughout the procedure, mothers report sometimes feeling uncomfortable about not being able to move their legs, or may feel queasy when the obstetricians are pulling at different layers when they are operating. Mothers report feeling touch throughout, but you should very little pain. Most mothers also have shivering that lasts through the procedure. This is more a nuisance than anything else.
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