Uniport and Multiport Epidural Catheters in Post-surgical Patients

Epidural analgesia (pain relief) is an effective treatment for post-surgical acute pain. The
factors that determine the effectiveness of pain relief with epidural analgesia have been
studied almost exclusively in the lumbar (low back) spaces for obstetrics (childbirth). These
factors include the design of the epidural catheter, the type and dose of medications, and
the volume of solution used. One of the important issues specific to the catheter design is
whether the tip has a one end-hole, or multiple side holes. The number of holes has been
suggested to affect the spread of epidural anesthetic over time, especially with low volume
solutions. This has been demonstrated in older, stiffer epidural catheter designs, but has
not been shown to be true with the newer, flexible epidural catheters.

The thoracic (upper back) epidural analgesia is widely employed for a many types of surgical
pain. While the mechanism of pain relief is similar to that in the lumbar space, there may be
differences between the two sites. Firstly, thoracic catheters tend to use low volume, high
concentration medication solutions, which likely do not spread as effectively. Secondly, the
thoracic catheters often need to be used for prolonged periods of time. Whereas the typical
obstetric epidural is used for less than 12 hours, the post-surgical catheter is typically
required for one to three days (or more). Finally, the thoracic space is narrow, with a
thinner thecal sac, which might promote a difference in the spread of epidural solution.

Thoracic epidural analgesia is routinely used to control post-operative pain for a wide
variety of surgical procedures. Based on the improved effectiveness of the one end-hole
flexible epidural catheter in obstetrics, this design is commonly used in thoracic epidural
analgesia. It has been observed that thoracic epidurals are somewhat less effective after a
period of time when compared to the effectiveness of labor epidurals. This may be in part due
to the inappropriate assumption that the thoracic epidural space of a post-surgical patient
is the same as the lumbar space of a parturient.

The investigators seek to determine whether there is a difference in the analgesia provided
by a thoracic multi-port epidural catheter when compared to a thoracic uniport epidural
catheter as measured by pain scores, medication given for breakthrough pain, and need to add
intravenous opioids. As mentioned previously, these catheters have been studied extensively
in laboring patients but there is a striking paucity of literature regarding how anesthetic
solutions spread in the thoracic epidural spaces of non-pregnant post-surgical patients and
how this may be affected by catheter type. If the hypothesis is supported by results, it may
change the practice within the study institution, and possibly, on a much larger scale. This
study may also provide a foundation for further research into the physiology of the thoracic
epidural space, how it differs from the lumbar epidural space, and how a medication solution
spreads within this unique space.

Inclusion Criteria:

- English speaking

- Surgery in the thorax or upper abdomen

- Age between 18 and 75

- Expected use of epidural analgesia for >24 hours

Exclusion Criteria:

- Contraindication to epidural catheterization

- Chronic use of opioids

- Chronic pain

- Allergy to the standard medications used

- Body Mass Index >40

- Delirium

- Dementia