Treatments: UAE: Sedation: Regional Analgesia

First, some anatomy - The spinal cord and the nerves that are its branches live in a bag of fluid called the thecal sac that runs down the middle of the spine. The cord itself ends just below the junction of the portions called thoracic and lumbar (just below the level of the brassiere strap in the back). Below that are only the nerves which take and receive signals to/from your lower abdomen, pelvis, and legs. (NOTE: This is a simplification. There's a lot of detail I'm leaving out, but it isn't particularly relevant.) Between the thecal sac and the surrounding rings of bone one finds fat and loose connective tissue. This region is collectively called the epidural space—even though it isn't empty. The nerves have to cross the epidural space as they leave the thecal sac for the rest of the body.

In SPINAL anesthesia, a tiny needle (I use a 27G needle) is inserted into the thecal sac in the lower lumbar region. This is called a lumbar puncture. One of the slang terms for it is spinal tap. LPs are done for a lot of reasons - to obtain a sample of the fluid that the nerves live in (called cerebrospinal fluid or CSF) in patients who have or may have a variety of diseases, for myelography, etc. Once the needle is in position, a small amount of medication is injected directly into the sac, where it has direct contact with the nerves. The needle is removed, leaving nothing in place but the medication.

In EPIDURAL anesthesia, a somewhat larger needle is placed in the epidural space (it's a technical error if you enter the thecal sac). In most cases, a small catheter is then threaded into the epidural space. Medication can be administered through the catheter to bathe the nerves as they cross the space. This relies on the medication diffusing properly through and around all of the assorted tissues in the epidural space. When no longer needed the catheter is removed.

• Advantages of Spinal
  • Rapid (about 5 minutes)
  • Gives 10-12 hours of pain relief
  • More reliable than epidural, since medication is injected into a fluid with which it mixes well, rather than into a space containing a variety of tisseus through which it must percolate
  • Very small dose of medication
  • Don't have to worry about catheter (where it goes, breaking off, etc)
  • Does not effect one's ability to walk, move, etc. (in the doses I use)
  Disadvantages of Spinal
  • Risk of "spinal headache" - about 1%
  • Cannot add to dose without repeating procedure
  Advantages of Epidural
  • Doesn't invade thecal sac
  • Can repeat or add to dose if needed
  • Also gives 10-12 hours of pain relief
  Disadvantages of Epidural
  • If thecal sac is punctured, the risk of spinal headache is higher (~5%).
  • If the catheter is placed into the thecal sac rather than into the epidural space and this is not recognized, the larger dose of medications can lead to a severe or life-threatening complication.
  • Have to worry about catheter
  • Not as reliably effective, can have more effect on one side than the other, etc.
  • If additional meds are needed, the dose can become high enough to interfere with the patients ability to move their legs or control their bladder for hours after the procedure.
  • Epidural anesthesia requires the involvement of an anesthesiologist, adding expense and scheduling issues to the procedure.

I feel that for UAE patients the potential disadvantages of epidural far outweigh any advantage it may have over spinal, so I do not make epidural analgesia available as a choice.

Patients receiving spinal analgesia also get some sedation (a medication related to Valium™) through their IV as a relaxant during the procedure. All patients also get a dose of an anti-inflammatory medication related to Motrin™ during the procedure.

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