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Intrathecal Narcotics for Labor Analgesia

(Originally posted 31 August 1997 on About Anesthesiology)

Intrathecal narcotics is a technique which represents a subset of what is known as spinal anesthesia. The technique involves placing a small dose of a narcotic such as Sufentanil (or a combination of narcotics such as Sufentanil combined with Morphine) in the intrathecal space (the fluid-filled space immediately surrounding the spinal cord) to provide analgesia (pain relief) for labor.

The technique is not widely used for labor, probably because it provides only analgesia (pain relief) and not anesthesia (lack of pain). Although it presents some significant advantages for the laboring patient (which we will discuss next), one of the disadvantages is that it provides a lower level of pain control when compared to an epidural technique. However, I believe that it is important to remember that each person requires a different amount of pain relief and that the relief provided by intrathecal narcotics is likely sufficient for many patients. It is my personal opinion that many people promote epidurals blindly or too aggressively and that intrathecal narcotics is an often underutilized technique.

There are some other disadvantages of an intrathecal narcotic. Placing of an intrathecal narcotic involved placing a needle through a membrane called the dura which surrounds the fluid in the space. This results in a small chance of headache after the technique is completed (a so-called post-dural puncture headache). Although this headache is not likely to be life threatening and is treatable, it can be a very bothersome complications should it occur. It is estimated to occur in up to 1-2% of laboring patients that receive intrathecal narcotics.

Other common complications are also bothersome, but rarely dangerous. These include nausea and vomiting, pruritis (itching) and urinary retention. All of these are treatable should they occur. There are a few more serious complications such as epidural hematoma and respiratory depression which fortunately are extremely rare. Your anesthesiologist can give you more information about these more severe complications.

The other drawback of an intrathecal is that it is a "one-shot" technique. This means that once the medication is placed, the effect of the medication is time-limited. This is unlike and epidural where a catheter is placed in the body to allow continuous application of medication or intermittent repeat administration of additional medication. Of course, an intrathecal could always be repeated but this involved another needle stick for the patient. To minimize the effect of this limitation, a combination of narcotics is often used. One example is the use of Sufentanil (a fast acting narcotic with a duration of about 45 minutes) combined with Morphine (takes about 45-60 minutes to start working but lasts 18-24 hours).

The advantages of an intrathecal include ease and speed of placement as well as almost immediate pain relief (an epidural usually takes about ten minutes to start working). In addition the patient is able to move, walk, and push without any muscle weakness. The risk of hypotension (a drop in blood pressure) is significantly reduced in comparison to epidurals. There also is some evidence in the anesthesia and obstetrical literature that suggests that there is a smaller risk of caesarean section, prolonged labor, and forceps delivery when intrathecal is utilized versus when an epidural is utilized.

Some anesthesiologists will add a small amount of dilute local anesthetics to the narcotic solution in an attempt to increase the level of pain relief that results from an intrathecal. In my experience, this is an effective technique which I often utilize. It does increase the likelihood of numbness of the legs, weakness of the legs and a drop in blood pressure, but only very slightly. It is a good alternative for patients that need a higher level of relief but do not wish to have an epidural.

Another technique to avoid some of the drawbacks of an intrathecal (limited duration, less control of pain, etc.) is to combine an intrathecal technique for immediate relief with an epidural catheter for "backup" if the patient needs more pain relief or longer pain relief. This technique has its own advantages and disadvantages. This so-called combined spinal-epidural technique is the basis for what is known as the "walking epidural" and is the topic of this article.


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