So, let’s continue the topic of the different types of anesthetic options for labor with a discussion of Spinal Anesthesia. I get a lot of questions asking about Spinals (not the ’80’s rock band) and the differences between spinals and epidurals (they are not the same) and this month we will focus on spinal anesthesia and when it is used… Don’t forget you can always ask questions about this or other medical topics through the “Ask a Question” link on the website located here.

What is a Spinal Anesthetic?

A spinal is not the same as an epidural (for information on epidurals - see January ‘08 archive). Although somewhat similar, a spinal for labor is done with a needle inserted into the lower back. However, the epidural delivers anesthetic medicines into the space just above the dural membrane (which covers the spinal cord, nerve roots and spinal fluid), where as a “spinal” advances into this space and directs the medicine into the clear fluid (CSF) that surrounds the spinal cord.

Whereas a working epidural can be used for both relief of labor pain and for a c-section; spinal anesthesia is typically used only for c-sections or instrumented delivery. Spinal anesthesia delivers a small amount of concentrated anesthetic directly into the space that contains the spinal cord, which allows it to mix with the cerebrospinal fluid (CSF) and directly bathe the spinal cord. This creates a concentrated anesthetic at the lower levels of the spinal cord, which causes a numbing sensation to the lower half of the body and provides the necessary anesthesia for a c-section.

Unlike an epidural, a “spinal” has a quicker onset and is a stronger, denser anesthetic which can be used for c-sections. There is no attached catheter with a spinal, as there is with an epidural (unless a CSE is used – see below), so once the medication is administered, there is no option for re-dosing. Depending on the type and amount of anesthetic used, a spinal anesthetic will last anywhere from 1½-3 hours, which is usually long enough for most c-sections. Your anesthesiologist will always test your spinal or epidural before a c-section, so there is no need to worry about feeling any of the pain related to a c-section (although it is still common for women to feel “pulling” or “pushing” sensations during their section). You should also be aware that there is always the risk that your spinal will not work effectively, and other anesthetic types such as general anesthesia may be necessary (although rare).

Is it safe?

As you might imagine, it might be very frightening to enter the spinal space with a needle; however anesthesiologists use several techniques to minimize the risks to patients having a spinal anesthetic (notice how in this picture the husbands look more nervous than their wives… which is a common portrayal on the obstetric ward).

1. Level – The spinal cord is surrounded by several structures that not only encase it, but serve to protect it. The actual “spinal cord” ends at what is referred to as the L2 level (see picture – just below the middle of the back); and typically puncture in the area above this L2 level can be associated with a slight risk of damaging the spinal cord. Fortunately, during a spinal anesthetic the L3-L4 inter-space or below this level, is used which significantly reduces the possibility of accidentally injuring one of the spinal nerves or its roots during a spinal anesthetic.
   

2. Smaller needle – You’ll be happy to know that the size of a spinal needle (thickness) is much smaller than the needle for an epidural. It should not really make a difference because your anesthesiologist will inject plenty of local anesthetic into the skin before the introduction of this needle but it will make a difference in terms of your safety. Using a smaller needle there is less chance of injuring an adjacent structure or nerve and a lower possibility of developing a “spinal headache”, which can still occur (more on this next month…).

3. Less Drugs – Many women are concerned about the effects of anesthetics on their baby; a spinal technique delivers medication directly into the area incasing the spinal cord, which is the area that modulates the interpretation of sensation and pain. By delivering medication directly to this area, lower amounts of medications are needed to achieve their desired effects.

4. Speak Up! - You are the best help to your anesthesiologist! If you feel a certain sharp pain, numbness or tingling sensation when the spinal is being placed, you should AVOID SUDDEN MOVEMENT and let them know so they can adjust the position of their needle and prevent any possible injury.

Risks of Spinal Anesthesia

1. Effects on blood pressure and heart rate –Hypotension (low blood pressure) and bradycardia (low heart rate) can both occur with spinal anesthesia. The effect on blood pressure is enhanced in dehydrated patients, and usually requires the administration of intravenous fluids. If you develop nausea or lightheadedness, it may be a sign that your blood pressure is low and requires treatment.

2. Headache – A postdural puncture headache (PDPH) or “spinal headache” can occur. This headache typically worsens when trying to sit upright, and is relieved with lying flat. The headache is typically located in the back of the head and radiated into the neck, and when severe can be accompanied by ringing in the ears, blurred or double vision. This headache typically starts 24-48 hours postoperatively and is thought to occur due to the leakage of fluid (CSF) out of the spinal space which creates a change in pressure - from the hole created by the spinal needle (reason why such a thin needle is used). The risk of PDPH following a spinal anesthetic is approximately 1-5%. The headache is not permanent and typically resolves with either conservative measures (bed rest, IV fluids, or analgesics) and/or caffeine. When severe or if symptoms persist, an epidural blood patch may be performed (More information on spinal headaches and their treatments next month…). Other causes of severe headache should be considered in these situations including meningitis and arachnoiditis.

3. Paresthesias – A paresthesia is a sensation of tingling, pricking, or numbness (pins and needles) in the skin which typically has no apparent long-term physical effect, and is due to direct trauma from placement of the spinal needle or injection of anesthetic into a spinal nerve. Although rare, permanent neurologic impairment can occur, and requires prompt evaluation by a neurologist which can significantly improve outcome.

4. Backache – Mild pain in the area of the back where the needle was inserted can occur. Generalized back pain is also common, however it usually resolves on its own. The etiology of this pain is believed to be secondary to changes that occur with pregnancy and labor as the rates of back pain are equal in women who had epidurals and spinals compared to those who did not.

5. Infection – The risk of infection with spinal anesthesia is exceedingly rare due to improvements in sterile technique. Nevertheless, meningitis, arachnoiditis, and epidural abscess although very rare can still occur – see below.

6. Meningitis – Meningitis is an inflammation of the membranes that cover the brain and spinal cord, which is a serious but treatable complication. The risk of meningitis is the most common of the “rare neurological complications” occurring in an estimated 1 out of 100,000 patients or at a rate of 0.001%.

7. Epidural Abscess - The development of spinal epidural abscess after an epidural is extremely rare and estimated to occur in 1 out of 505,000 patients or at a rate of 0.0001%. This rare complication can be life threatening and can present with signs of back pain, incontinence and neurological symptoms.

What is a Combined Spinal Epidural (CSE)?

A combined spinal–epidural has the benefits of both types of anesthetics. The needle is inserted into the epidural space and then a thinner needle is guided into the spinal space to inject medicine into the spinal canal. Once this is done, the spinal needle is removed but a thin catheter (just like in a regular epidural) is left in place. The spinal part helps provide immediate pain relief; the epidural portion allows drugs to be continuously given and for longer periods of time. A CSE is ideal in repeat c-sections or situations of a prolonged or more complicated labor. Although it is still a bit controversial, it does not appear that a CSE increases the risk of developing a PDPH or “spinal headache”. It is not believed that the risks involved in a CSE are any greater than those associated with the placement of an epidural.

For those of you who want to see the steps involved in a spinal anesthetic here is a video that accurately portrays this process. Click here to view: http://www.operationalmedicine.org/ed2/Video/Spinal.mpg (courtesy of Operational Obstetrics & Gynecology).

I hope this helped clarify some of the differences between a spinal and an epidural for labor. If you have any questions or comments please email them to askthedrs@thebumblecollection.com. Remember you can also submit a question to the website through the "Ask a Question" link.

Next month, we will review post-dural puncture headaches (PDPH) a.k.a. "spinal headaches" and their treatments.