Overview of Epidural Anesthesia
Epidural anesthesia is a type of pain control method that involves injecting numbing medications into a specific area surrounding the spinal cord known as the ‘epidural space’. This method helps to numb the regions of the body serviced by the nerves in the chest, stomach, pelvis, and lower body. The epidural technique can be used to manage pain during surgery, long-term pain, or muscle tightness. It can be used as the main method of pain relief or in addition to other pain relieving strategies.
Epidural anesthesia has been used successfully for over 100 years and offers many benefits compared to other types of anesthesia. One of the main benefits is that healthcare providers can customize the type of medication used and the method of delivery (such as one-time injection or continuous infusion) based on the individual needs of the patient. Additionally, it can decrease the need for opioid pain medications, which are commonly associated with unwanted side effects, during and after a procedure. This aspect is particularly important for children, as there is ongoing debate about the impact of certain anesthetics on their brain development. Using the epidural technique, we can also better manage post-surgery pain as part of a comprehensive pain management plan. Moreover, it was proven useful in providing an alternative to types of anesthesia that may spread airborne particles during the COVID-19 pandemic.
However, recent research suggests there might be other methods of anesthesia that could be more beneficial and less invasive than epidural anesthesia. There are also certain risks and complications related to the epidural procedure. Therefore, it is critical for medical professionals to know when epidural anesthesia should and shouldn’t be used, to understand the benefits, risks, and potential complications, and to be familiar with the current recommended practices for performing it. This knowledge also helps coordinate better care for patients who undergo the procedure, leading to improved outcomes.
Anatomy and Physiology of Epidural Anesthesia
The spinal cord in adults is around 45 cm shorter than the spinal canal, usually ending around the first or second bone in the lower back (the L1 or L2 vertebra). In newborn babies, the spinal cord ends at the same place. Below this, the nerves coming from the lower back and pelvis area join together to form what’s known as the cauda equina. The entire spinal cord is suspended in a fluid called cerebrospinal fluid and encased in a protective layer called the arachnoid mater. This arachnoid layer extends lower in children and newborns than in adults.
Right around the spinal cord is a space called the spinal epidural space, which stretches from the base of the skull all the way down to the lower spine. This space contains tissues, blood vessels, and lymphatic channels (which transport lymph fluid). The size of this space can enlarge in conditions like pregnancy or a medical condition called ascites, which increases the risk of damaging it during procedures. The epidural space has an anterior (front) part and a posterior (back) part, each containing different structures such as nerves and veins.
To understand where the epidural space is, imagine boundaries formed by different layers of tissue around it. Inside, it’s bounded by the protective layers of the spinal cord (the dura and arachnoid maters). Outside, it’s bounded by a ligament (the ligamentum flavum) and the cover of the spinal bones (the vertebral periosteum). The distance between the skin and the epidural space can vary depending on your age and amount of body fat.
This anatomy is very important when it comes to administering epidural anesthesia, a type of pain relief used often during childbirth and other procedures. Anesthesiologists need to understand where everything is, including vessels and nerves, in order to safely place an epidural catheter to deliver the anesthesia. Various techniques are used to find and access the epidural space safely. Traditionally, this involves identifying certain anatomical landmarks on your back to guide the needle.
One specific technique called a caudal epidural block involves injecting anesthetics into a space near the lower end of your spine. It’s used often in children and for certain procedures in adults. Knowing the specific measurements and features of this lower spine area is crucial for this procedure. Things like shape and length of certain structures can vary from person to person and can even contribute to lower back pain or affect certain surgeries. Even with the right understanding and planning, a caudal epidural block can be unsuccessfully administered about 30% of the time, often because everyone’s anatomy is a bit different. This is why today, ultrasound is often used to help guide placement.
Why do People Need Epidural Anesthesia
Epidural anesthesia, a type of pain relief method, is commonly used during childbirth and during certain significant surgeries involving the chest, belly, or spine, especially when there’s no need to completely relax the muscles. It can also serve as a support tool to help manage pain during or after an operation. It’s particularly beneficial for patients who have a higher risk of post-surgery complications, such as those with heart disease. These high-risk patients have shown increased benefits, like fewer post-surgery lung complications and quicker return of gut function, after the use of epidural anesthesia.
A detailed review of studies that compared patient-controlled pain relief delivered either through the veins (intravenous) or through the spine (epidural) in abdominal surgery has shown that epidural methods are linked to better pain relief after surgery, reduction in opioid use, and fewer post-surgery complications. Furthermore, epidural anesthesia, when combined with standard painkillers, has been shown to decrease memory and thinking issues in patients who received general anesthesia. Additionally, some studies suggest that epidural pain relief could be linked to better survival rates in patients post-surgery, possibly due to its effect on cancer recurrence.
However, other more recent studies indicate that the benefits of using epidural pain relief during surgery aren’t as apparent when compared to other alternatives, such as pain relief medications given directly in the wound or those targeting specific nerves. These alternatives come with a lower risk of complications. Current studies suggest that epidural anesthesia might provide slightly better relief from post-surgery pain than drugs given through the veins. Even so, non-childbirth related usage of epidural anesthesia may be more suitable as a supplementary therapy, alongside other primary pain relief methods. More research is necessary to conclusively establish these findings.
When a Person Should Avoid Epidural Anesthesia
Getting epidural anesthesia is generally safe for most patients. Still, there may be other types of pain relief methods that are better suited for particular individuals.
There are some circumstances, known as absolute contraindications, where you should definitely not have an epidural:
- If you, as the patient, do not want the epidural.
- If there’s an infection on your back where the needle needs to go in.
- If the pressure inside your skull is too high — this is a condition known as increased intracranial pressure.
- If you’ve recently experienced a traumatic injury to your spinal cord.
There are also less clear-cut situations, named relative contraindications, where an epidural might not be the best option:
- If you’re struggling to maintain steady blood pressure — a condition known as hemodynamic instability.
- If you have a heart condition called obstructive cardiomyopathy, where the walls of your heart are too thick.
- If you have a blood disorder that makes it difficult to stop bleeding, known as uncorrectable coagulopathy, or if you are on medication to prevent blood clots.
- If you have thrombocytopenia, a condition where you have low platelet levels in your blood. Platelets help your blood to clot.
- If you would find it difficult to remain still in the right position for an epidural to be placed.
- If you have abnormal spinal structures or issues with your spine.
Equipment used for Epidural Anesthesia
There are several types of needles used for an epidural, such as Tuohy, Hustead, Crawford, and Weiss. However, the most commonly used is the Tuohy needle. These needles are usually 17 or 18 gauge (which refers to the thickness of the needle) and are 3.5 inches long. For patients who have more body fat, longer needles of up to 6 inches can be used.
In performing an epidural, a special syringe known as a “loss of resistance” syringe is used. This syringe, which can be made of glass or plastic, is designed to clearly detect the change in resistance when the needle reaches the epidural space (where the medication is injected). The syringe may be filled with air or saline and the choice of filling doesn’t affect the success of identifying the epidural space or the risk of complications.
For continuous pain relief, an epidural catheter is used. These thin tubes, which can be flexible or stiff, have one or more holes to allow the pain relief medication to flow through. These kits also come with secure connections to attach the catheter to the syringe.
It’s important to keep the area where the epidural is inserted clean to prevent infection. This would involve wearing sterile gloves, surgical cap, and mask, using sterile coverings and a skin cleaning solution, and applying a sterile dressing after the procedure.
The medications used in an epidural will vary, but typically include a local anesthetic like bupivacaine or ropivacaine, and a strong painkiller like fentanyl or sufentanil. IV fluids are also typically given before an epidural to prevent low blood pressure. Medications to treat low blood pressure should be nearby in case they’re needed during the procedure.
Some doctors use ultrasound guidance to help place the epidural catheter. This technology allows the doctor to see the relevant structures in real time, making the procedure potentially safer and more precise. Using ultrasound guidance can help better identify the epidural space, reduce the number of needle passes and attempts, and lower the risk of complications like unintentional dural puncture (accidentally piercing a layer of the spine), infection, and bruising. However, more research is still needed to prove that ultrasound-guided methods are superior to traditional ones.
Who is needed to perform Epidural Anesthesia?
The anesthesiologist or nurse anesthetist is a professional trained to administer medications that will make you sleep or numb during the procedure. They’ll make sure you’re not feeling pain during the operation. Assisting personnel are other healthcare professionals who help during the whole process. They ensure everything runs smoothly and assist the surgeon as needed.
Preparing for Epidural Anesthesia
Before getting an epidural, which is a type of anesthesia that numbs certain parts of the body, the doctor will ensure you are positioned correctly and that the area to be treated is properly prepared. It’s also important to have emergency equipment and medicines ready in case they’re needed during the procedure. To give you fluids or medicines through a vein, the doctor will put in an IV (intravenous) line. The doctor will also follow standard preanesthesia guidelines, which include preliminary testing and monitoring your blood pressure, heart rate, and other vital signs.
The doctor can position you in a couple of different ways for an epidural, either sitting or lying on your side. Arching your back can help the doctor have better access to the space between your spinal bones where the epidural is placed. The doctor will use a special sterile method to keep everything clean during the procedure, which is important to prevent infection.
The doctor will identify the correct spot for the epidural using certain landmarks on your body, a special needle, and sometimes with the help of an ultrasound. Studies have shown using an ultrasound for guidance can make the procedure quicker and more successful. It can also reduce the number of needle attempts and improve the overall outcomes, meaning fewer needle pokes for you and a reduced chance of complications. This is the reason why some doctors prefer to use ultrasound-guided techniques for this process.
How is Epidural Anesthesia performed
How a doctor performs epidural anesthesia, which is a type of pain relief used during surgeries, depends on the specific area of the spine that needs to be accessed. For access above a particular section of your spine (T11 vertebra), they would usually use what’s called a paramedian approach due to the hard-to-reach angles of the individual bones. For areas below the T11 vertebra, a midline approach is usually used.
In a midline approach, the doctor will insert the needle in the middle of the small spaces created by the spinal bones. To make this less painful, a numbing medicine called lidocaine is used. The needle is slowly pushed through various tissues and ligaments until it reaches the epidural space. The doctor will know if they’ve reached the epidural space by noting a loss of resistance while pushing a saline-filled syringe attached to the needle.
Alternatively, in a paramedian approach, the needle is inserted about 1 cm to the side of the spaces between the spinal bones. Again, lidocaine is used for numbing and the needle is pushed through different tissues. The crucial difference here is this approach does not require the needle to pass through two specific ligaments, called the supraspinous or interspinous ligaments.
Once the epidural space is reached by either approach, a thin tube, or catheter, is inserted through the needle. The needle is then removed and the catheter is left in place to help manage your pain. The catheter is checked to make sure it is not placed in the fluid-filled space around your spinal cord. If this happens, the catheter has to be relocated.
Lastly, a variation of epidural anesthesia called caudal anesthesia is sometimes used in kids for procedures below the belly button. The procedure works similarly to a regular epidural but with a few variations in the location prepared for the needle and how it’s inserted.
Possible Complications of Epidural Anesthesia
Damage to the spinal cord as a result of anesthesia during surgery is rare, but it can have a serious impact on the patient’s quality of life and at worst, can be life-threatening. Potential problems caused by this type of injury range from temporary or permanent changes in nerve function, a buildup of blood or pus near the spine, direct injury to the spinal cord itself, and a painful condition caused by inflammation of the thin layer covering the brain and spinal cord. These problems can lead to muscle weakness, loss of sensation, pain, abnormal sensations such as tingling, or in severe cases, permanent paralysis or numbness.
Some people have a higher risk of spinal cord injury from anesthesia. These include people born with abnormal spinal canals, the very young or old, overweight individuals, those with diabetes, people with weakened immune systems or serious illness, and those with previously existing nerve diseases. It’s important for doctors to carefully review these patients before surgery to identify any health conditions that might increase the risk of spinal cord injury. However, handling patients with spinal cord injury in emergency rooms can be especially complex because of existing damaged tissue.
There are also other issues that might arise from a type of anesthesia known as epidural anesthesia. These include low blood pressure, nausea and vomiting, narrowing of the airways in the lungs, headache after accidental piercing of the membrane surrounding the spinal cord, temporary nerve disorders, nerve injury that may lead to nerve disease, localized bleeding, and infections.
The wrong placement of the anesthesia injection could also result in total spinal anesthesia, an infection in the spine, or inflammation of the bone.
What Else Should I Know About Epidural Anesthesia?
Epidural anesthesia, a method that’s been used for a long time in the medical field, is a safe technique when done correctly. This practice can limit the need for general anesthesia, which may come with added risks. It can also reduce the number of opioids used both during and after the procedure, which in turn lowers the chances of experiencing side effects linked with these medicines. This is especially important for children, since there’s ongoing discussion about how certain anesthetic drugs might influence brain development. The epidural method is also effective for managing pain after surgery.
In light of the COVID-19 pandemic, epidural anesthesia served as a substitute for general anesthesia, which involved aerosol generation and thus, posed a risk for viral transmission.
However, it’s important to recognize that while epidural anesthesia offers strong pain relief and improved outcomes following surgery, it also has inherent risks. Therefore, it’s crucial that each patient undergoing this process is chosen carefully, monitored closely, and acted upon quickly if complications arise.
Despite potential issues, anesthesia techniques like the epidural remain some of the best options for preventing and managing pain without relying heavily on opioids. These approaches can lessen patient suffering, improve results, shorten hospital stays, and reduce the chance of long-term pain, ultimately saving money. Therefore, while epidural anesthesia is a valuable tool for managing pain, it comes with risks. Correct patient selection, monitoring, and prompt action are necessary to minimize the risk of complications, such as spinal cord injury caused by anesthesia.
More research is needed, along with improvements to our anesthesia methods, to increase patient safety during procedures involving the spinal nerves.