#458: Nursing Guide to Neuraxial Analgesia

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Neuraxial analgesia is a type of regional anesthesia that utilizes local anesthetics or a combination of local anesthetics and opioids to produce sensory blockade. Spinal blocks and epidurals fall into this category. Common uses include abdominal, pelvic, and orthopedic surgeries as well as labor and delivery. Higher level epidural administration can also be utilized for thoracic surgery as well.

Differences between epidural and spinal anesthesia

The key difference between epidural and spinal anesthesia is where the anesthetic is administered. 

• Epidural – Anesthetic agents are injected into the epidural space. This can be done via a single injection, but it is more common for an epidural catheter to be placed for a slow, continuous infusion and long-lasting pain management. 
• Spinal – The anesthetic agent is injected into the CSF of the intrathecal space, numbing the nerves that exit the spinal cord. Spinal anesthesia is typically administered as a single injection (sometimes called a “single-shot” in the clinical setting.”

Other key differences between these two types of neuraxial analgesia include the onset, duration, and degree of motor block. Here’s a quick summary 👇

What are dermatomes?

An important concept in neuraxial analgesia is dermatomes. A dermatome is an area of skin that sends sensory information to the brain through a specific spinal nerve. You can picture the body divided into horizontal “strips,” each served by its own nerve root.

When we use neuraxial anesthesia, we’re trying to block sensation at certain dermatomes. These are mainly the thoracic and lumbar levels, depending on the surgical location. To get the right effect, the anesthetic doesn’t need to be injected exactly at the dermatome level. However, it must be placed in the spinal space (epidural or intrathecal), and allowed to spread upward or downward until it reaches the dermatomes we want to block.

In other words, the level of the block must match the level of the surgical site. For example, a C-section requires a sensory block up to the T4 dermatome (around the nipple line). For a knee procedure, the goal is to block sensation from the dermatomes that supply the knee and lower leg, which are mainly around L2–L4 (which correspond to the front of the thigh and knee region.)

We’ll talk more about dermatomes when we dive into assessment. But first, let’s talk about the order of blockade.

Order of blockade with neuraxial analgesia

It’s important to note that neuraxial anesthesia doesn’t block all nerve fibers at the same time. Different types of nerve fibers have different diameters and levels of myelination, which determines how quickly they’re affected. This is why patients lose certain sensations before others.

• Sympathetic fibers are blocked first, which leads to vasodilation and hypotension. The legs may feel warm during this phase as well. 
• Pain and temperature are blocked next. This leads to loss of cold sensation, which is why ice testing works so well to determine if a block is alleviating pain at that specific dermatome level.
• Touch and pressure are next
• Motor fibers are last, so motor function is the last function the patient loses as the block takes effect. With spinal anesthesia, the patient will be unable to move the legs. With epidurals, the legs will likely still have some movement but the legs will feel heavy and weak.

As the block resolves, it will do so in reverse order. Motor function comes back, then touch, then pain, then the sympathetic function. 

Pharmacology of neuraxial analgesia

There are three types of medications used in neuraxial analgesia – local anesthetics, opioids, and epinephrine. 

• Local anesthetics – Commonly used local anesthetics include lidocaine, ropivacaine and bupivacaine. These medications block the transmission of pain impulses, producing analgesia. Though locally administered, these medications can have a systemic effect, which can lead to local anesthetic systemic toxicity (LAST). For a deep dive into local anesthetics and LAST, check out this article here. 
• Opioids – Opioids are commonly used for neuraxial analgesia and may be administered as solo therapy or in combination with a local anesthetic. When opioids are utilized, respiratory depression and hypotension can result (and in some cases, can be significant).
• Epinephrine – Epinephrine is utilized to prolong the duration of local anesthetics by causing vasoconstriction at the site, which slows the systemic absorption of the anesthetic. Note the patient could have a transient tachycardia with epinephrine administration. The recommended concentration of epinephrine is 1:10,000 (the same concentration utilized for IV administration). 

Side effects and complications of neuraxial analgesia

• Physiologic effects – These include hypothermia, hypotension, bradycardia, and feelings of sedation. They occur due to the blocking of sympathetic, motor, and sensory nerves as well as unopposed parasympathetic tone. Treatment is aimed at addressing the specific physiologic effect. Note that hypotension occurs in up to 47% of cases and is more likely to occur in patients who are fluid volume deficient and in those receiving opioids via intrathecal or epidural routes.
• Post-dural puncture headache (PDPH) – Occurs when the dura is punctured, which causes a minor leak of CSF. It is exacerbated in the sitting or standing position. Associated symptoms can include nausea, vomiting, neck stiffness, dizziness, tinnitus, vision changes, and hearing loss. Treatment involves hydration, analgesics, and avoiding an upright position. Caffeine may also be helpful. For persistent cases, an epidural blood patch may need to be placed.
• Urinary retention – Neuraxial analgesia blocks afferent nerve signals to the bladder, leading to urinary retention. More likely with spinal blocks, but can occur with epidurals also.
• Backache – More common with epidural anesthesia and though mild, can last several days.
• Nerve injury – Though rare, direct trauma to nerve tissue is possible.
• Spinal hematoma – If not treated promptly, a spinal hematoma can cause irreversible damage and paralysis. It is especially high risk if the patient is anticoagulated and is more common in epidurals than spinal blocks. 
• Transient neurological syndrome (TNS) – This syndrome involves pain and/or burning and tingling in the lower extremities or buttocks after the spinal resolves. It typically improves after a few days with ambulation and NSAIDs. More likely to occur with lidocaine and mepivacaine. 
• Local anesthetic systemic toxicity (LAST) – While LAST can occur with any administration of local anesthetics, it is more likely to occur with epidural anesthesia than spinal anesthesia due to the larger volumes of medication used for an epidural. Get a deep-dive into LAST here.
• Infection – CNS infections can occur with neuraxial anesthesia and is more prevalent amongst individuals who are immunocompromised or at higher risk for infection (diabetes, cancer etc…). Meningitis is more likely with spinal anesthesia while epidural infections are more likely to cause epidural abscesses.
• Falls – Due to motor and/or sensory blockade, patients receiving neuraxial analgesia are at high risk for falls. Ambulation should be postponed until sensation and function have returned.
• Specific things to watch for with a high-level neuraxial block (cervical spine) – The key thing to watch for here is rapidly ascending sensory, motor, and sympathetic block. This can lead to significant respiratory depression, paralysis of respiratory muscles, dyspnea, hypotension, bradycardia, difficulty swallowing, difficulty speaking and loss of consciousness.

Nursing assessment for neuraxial analgesia

Priority assessments for a patient who received or is actively receiving neuraxial analgesia includes hemodynamic status, respiratory status, sensory level, pain, and motor function. Of course, you’re also watching for any complications such as urinary retention, LAST, and hematoma.

• Hemodynamics – Because neuraxial analgesia blocks sympathetic functions, vasodilation and bradycardia can occur. Keep a close eye on blood pressure and heart rate. 
• Respiratory status – Respiratory status really comes into play with higher-level blocks or blocks that rise higher than expected. Watch your patient for signs of respiratory compromise such as dyspnea, low SpO2, hypoventilation, and difficulty speaking. If your patient is complaining of numbness and tingling in the hands, this could be a sign of a high block. If a high block was not intended, let the anesthesiologist know immediately.
• Sensory level – Ice testing is a quick and easy way to determine the level of the blockade. To perform ice testing, place some ice cubes in a glove and touch it to the patient’s skin somewhere unaffected by the block to determine if they are able to feel cold. This is your baseline. Next, place the ice at the level you expect sensation to be affected. Move downward to determine which dermatomes are affected by asking the patient if they feel the cold glove. A lack of sensation to cold indicates the block is effective in that area. For example, for a C-section, the block should reach T4 (nipple line), and for knee surgery, it should reach L2-L4. You should also move upward to identify if a higher-than-expected block is present.
• Pain – As with any patient receiving analgesia, you will be consistently monitoring the patient’s pain level. A higher pain score could mean the block is ineffective or there is some kind of complication such as nerve injury or TNS.
• Motor function – As the patient recovers from surgery, motor function will gradually return. Remember, motor function is more affected with spinal blocks than epidurals. Ask the patient to wiggle their toes, which is typically the first movement as the block resolves. As time passes, assess the patient’s ability to move the foot, bend the knee, and lift their buttocks off the bed. 

Want to quiz yourself on neuraxial analgesia? Check out Episode #459: PodQuiz – Neuraxial Analgesia and reinforce your memory.

For more articles on perioperative nursing, check out this list.

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Last Updated on January 6, 2026 by Maureen Osuna, MSN, RN