Epidural Needle

Epidural Needle: How They Work & What They Do?

An epidural injection can provide excellent, effective pain relief (analgesia) during both labor for childbirth and during and after an operation. The process of obtaining the injection, though can be daunting. The idea of placing an epidural needle in the back near the spinal cord has put many people off the idea of going through with an epidural during labor. But should people really be afraid of the epidural needle? Perhaps if we could demystify the process, more people would have access to a great form of pain relief.

Throughout this article, I will answer commonly asked questions such as why an epidural needle is so long, the typical size of the needle, and whether the needle hurt.

Epidural Needle Sizes

The Epidural needles come in a variety of sizes and lengths.

This variation in of the epidural needle size and length allows the needle to locate the epidural space (where the pain relief needs to be given) in the spinal canal from the patient’s back. 

epidural needle size

This allows the delivery of an anesthetic medication into the epidural space (located in the spine) through a small tube and creating an “epidural block” for the patient.

 So why are epidural needles larger than a standard hypodermic needle? The answer lies in their ability to deliver a tiny plastic tube, called an ‘epidural catheter’ through the needle and placed into the epidural space.

This epidural catheter can remain in the ‘epidural space’ and become the vehicle to administer an anesthetic medication continuously. This allows patients in labor to have excellent pain relief for several hours.

Epidural Needle Size Measurement – Gauge

The epidural needle sizes refer to the thickness of the needle and are related to the ‘gauge of the epidural needle.

A higher gauge needle equates to a thinner epidural needle. An 18G (thinner) or 16G (thicker) epidural needle is commonly used in adults.

Does an Epidural Needle Size Matter?

When it comes to complications associated with epidural needles, thinner needles seem to have less complications. A recent study has shown that when comparing an 18G vs. 16G epidural needle size.

When it comes to complications associated with epidurals needles, thinner needles seem better.

A recent study has shown that when comparing an 18G vs. 16G needle that has inadvertently passed through the epidural space and pierced the dura mater (thin membrane), those that had the larger needle were left at a higher risk of developing a headache, referred to as a Post Dural Puncture Headache, or PDPH ( causes a leak of cerebral spinal fluid into the epidural space).

Epidural Needle Length

Worried about the epidural needle length? Does an epidural need to be that long?

Epidural Needle length

I have seen many husbands supporting their partners in preparing for the procedure only to faint at the sight of an epidural needle length.

I can see in their eyes them questioning what the medical reason for an epidural needle needs to be so long? How does the anesthesiologist know how far the epidural needle has been inserted?

Epidural Needle Length – The Standard Size

An epidural needle must be long enough to reach the epidural space from the lumbar region of a patient’s back.

The average distance from the skin to the space in pregnant women is approximately 4.9cm. A commonly used needle length is 8cm (see photo above).

If a patient is obese, a longer epidural needle may be required to access the space.

How does the Anesthesiologist know how far the epidural needle has to be inserted?

To assist the anesthesiologist in knowing how far the needle has been advanced, marks are imprinted on the epidural needle.

Each centimeter of the epidural needle is marked with alternating black and silver colors. There are a variety of ways an anesthesiologist uses to identify when they are in the correct location.

A popular method is ‘loss of resistance’ in which there is a pressure difference when the epidural needle enters the correct location.

Types of Epidural Needles

By far, the most common needle used is the ‘Tuohy’ needle.

Touhy Epidural Needle

The unique feature of the Tuohy needle is that at the end of the needle, it has a directional tip that allows anesthesiologists to direct the epidural catheter as it exits the needle tip. 

This aids placement of the epidural catheter in the space. When an anesthetic agent is administered via the epidural catheter, it targets the appropriate nerves for the particular area of the body required to be blocked.

  The needle also contains a stylet, which remains in the needle when inserted into the skin. This stylet is designed to prevent a skin plug from blocking the needle before entering the space.

Tuohy needles can have Wings

 An evolutionary advantage to the Tuohy needle is that it can have “wings” added.

These wings are located at the hub of the needle. It makes the epidural needle easier to grasp with both hands for placement.

This needle hub design is preferred by many anesthesiologists who use the loss-of resistance technique.

Will having an epidural needle inserted hurt?

The thought of someone inserting an epidural needle into your back can be very daunting. However, you may not realize that before insertion of the epidural needle, the Anesthesiologist will take measures to ensure that the experience is as comfortable for you as possible. 

Before insertion, the Anesthesiologist will numb the region where the epidural needle will be inserted with a local anesthetic.

They do this by injecting a quick-acting local anesthetic with a very fine needle. Although there may be some discomfort as the local anesthetic is being infiltrated, it is a very short limiting before the numbing effect occurs. Some people describe the experience as a similar pain to a ‘mosquito bite.’

Once the local anesthetic has taken effect, the epidural needle will be inserted. Although you should not feel pain, you will still feel pressure from the insertion.

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