Anesthesia Associates of Southern Connecticut

Spinal and Epidural Anesthesia

These 2 techniques are often confused and each is described below.


This is a very old and reliable method of anesthesia, dating back to the end of the 19th century. It is an extraordinarily safe technique and is widely used.

Basically, medication is injected directly into the spinal fluid where it bathes the nerves just as they leave the spinal cord. Only tiny amounts of medication are required to achieve large effects. While many different medications have been used, anesthesiologists primarily use only two (pain specialists use some different ones):

  • Local anesthetics - when injected into the spinal fluid, these agents profoundly anesthetize the nerves as they leave the spinal cord. This causes the lower part of the body (from the toes all the way to the lower chest) to become totally numb. This provides ideal operating conditions for the surgeon, and a completely pain-free experience for the patient.
  • Opiates - also known as narcotics. A narcotic such as fentanyl, dilaudid, or morphine injected into the spinal fluid causes pain-killing effects on the nerves. There is no numbness or weakness associated with this technique, so it is not suitable for surgery. However, it is excellent for taking care of post-operative pain, and is widely used in obstetrics.

How is a spinal done?

A spinal can be done in either the sitting position or on the side. Usually a little sedation is given (unless you are pregnant.) The back is cleaned with an antiseptic such as betadine and a sterile drape is placed over the area.

The anesthesiologist will usually feel along the top of the hip bones - this is about at the level of the 4th lumbar vertebra (L4) and provides a landmark for the anesthesiologist.

The bumps you can see along the spines of thin people are called the spinous processes. The spinal needle is placed between 2 of these spinous processes, usually at around L3 or L4. Your anesthesiologist will press into your back to feel these bumps to find the correct location to place the spinal needle.

Once the correct spot is found, a little local anesthetic will be placed in the skin with a fine needle. This is usually no more than a little pinch. The skin is now numb. The spinal needle is then inserted until spinal fluid is seen coming from the needle. At this point, the medication is injected, the needle is removed, and you are placed into position. 

If the spinal is for surgery, in seconds you feel the onset of numbness in the legs. The full onset is usually in less than 5 minutes. If the spinal is for the injection of narcotics (see above), the onset of pain relief is usually within 5-10 minutes.


This is also an old and reliable technique. As with spinal anesthesia, it is extraordinarily safe and has survived the test of time.

In contrast to a spinal technique where a fine needle is advanced until spinal fluid is seen coming from the needle, an epidural needle is only advanced until the epidural space is encountered. This space is hit before the needle reaches the spinal fluid.

The nerves leaving the spinal cord (nerve roots) must go through the epidural space to get to their destinations throughout the body. Medications injected into the epidural space will anesthetize these nerves. The same medications used for a spinal are used for epidurals - see above.

How is an Epidural Done?

the technique is very similar to placing a spinal. Once the skin is numb, an epidural needle is advanced through the numb spot until the epidural space is encountered. The spinal fluid is not reached by the needle. This takes a little longer than a spinal, but is still usually extremely quick.

Once the needle is placed into the epidural space, a little medication is injected through the needle - this causes a pressure sensation in the back. Then a catheter (medical term for "tube") is inserted through the needle until it is about an inch or two into the epdural space. The needle is then removed, leaving the epidural catheter in place. The catheter is then taped to the back. Note that the catheter is about as thick as a strong kite string, so you do not even feel it when lying on your back.

Once the epidural catheter is secured, medication is injected through the catheter into the epidural space. The anesthetic sets up more slowly than a spinal anesthetic, usually taking about 15-20 minutes. The epidural can be dosed repeatedly or a continuous infusion of medication can be delivered with a specially designed pump. The anesthetic can be made to last as long as necessary, sometimes for periods of weeks to months in patients being treated for chronic pain syndromes.

What are the risks of spinal or epidural anesthesia?

Although extraordinarily safe and widely used, spinals and epidurals are not risk-free. The risks are as follows:

Headache - spinal headache occurs in about 1:100 patients. It is made much worse by sitting and relieved by lying down. This risk decreases with age, so that the risk of headache after the age of 60 or so is extremely low. If the headache is mild, it can be treated conservatively - fluids, rest, and caffeine. If it is more severe, it can be treated with an epidural blood patch. Click here for a description.

Decreased Blood Pressure - this is extremely common and often not noticed by the patient. Obstetric patients might feel dizzy or light-headed. The low blood pressure is quickly and easily corrected.

Nerve Damage - nerve damage, including paralysis, is extremely rare. The reported cases almost always result from bleeding into the spinal canal as a result of anticoagulants (blood thinners). For this reason, anesthesiologists will not do a spinal if your blood has been thinned from anticoagulants or from disease. Blood thinners will need to be stopped for a period of time if spinal (or epidural) anesthesia is planned.

Minor complications - these include itching and nausea.

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