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Treating Pain Before It Starts: Pre-emptive Analgesia
(Originally posted 6 December 1999 on About Anesthesiology)
Pain after an operation, or postoperative pain as it is known,
is frequent - occurring after almost every operation. While this
is to be expected, and while treatment for the pain is often given
with different types of medication and other methods, it remains
one of the issues that anesthesiologists and surgeons must deal
with in the treatment of their patients. It has long been theorized
that doing certain things before and injury (or in this
case a surgical incision) causes pain may actually decrease the
amount of pain afterwards - making it easier to obtain relief
for the patient while using less medications and causing less
side effects. This theory is what is known as "pre-emptive
analgesia".
There are a number of different ways to give medication to
a patient - including by mouth, intramuscular shots, intravenous
medications, epidural, intrathecal, and intra-articular routes.
In addition, a variety of different medications can be utilized
for pain relief - including such things as nonsteroidal anti-inflammatory
drugs, local anesthetics, narcotics, etc. It makes sense to utilize
these drugs to treat pain once it has begun - what could possibly
be gained by giving these medications in advance, before there
is any pain?
When you undergo surgery or have an injury of another kind,
nerves in the skin and tissues are activated that are the body's
way of sensing pain - these nerves then send signals to the spinal
cord. The impulses from these nerves then travel along the spinal
cord and to the brain - where they are interpreted as pain. Then,
the brain sends new signals back down the spinal cord and to the
site of injury. These nerves act as more than pathways however
- they change their function and the way they respond when they
are activated. The more pain signals that
nerves receive, the more sensitive they are to pain in the future
and the more signals they send to the spinal cord as a result.
So, in a sense, nerves prepare themselves for more pain - have
you ever noticed how an area that has been injured can be more
sensitive even after the healing and injury is over?
Now, one of the things that anesthesia does is block the patients
consciousness to the pain of surgery. For example, if the patient
is rendered unconscious, the brain does not register that the
impulses coming to it are signaling pain. However, the nerves
and the spinal cord are still receiving these signals - and still
undergoing the changes that make them even more sensitive to future
signals. Therefore, once the anesthesia wears off and the patient
awakens, the nerves and spinal cord are more than ready to signal
the patient that significant pain exists
Just a side note - some methods of anesthesia known as regional
anesthesia (for example a spinal or an epidural) do actually block
these nerve impulses at the level of the spinal cord. As a result,
there may be significant benefits to these forms of anesthesia
when it comes to the battle to reduce post-operative pain.
Pre-emptive analgesia seeks to break
this cycle of events before it begins. Utilizing drugs
to block pain impulses from reaching the spinal cord or preventing
the changes in nerves that occur that make them more sensitive
should, at least in theory, reduce the sensitivity of the patient
after surgery. The question now becomes - is there any proof that
it actually works?
A number of studies do exist that show pre-emptive analgesia
is a good plan to follow. For example, a report in the Journal of the American Medical
Association in early 1999 (editor note: when this article was originally written) showed that men undergoing prostate surgery who received pain
medication before the surgery started reported less pain
during the four days that they spent in the hospital. In addition,
when asked two months after the operation about pain, 86%
of patients that received medication before the surgery said they
had no lingering pain - compared to 47% of patients who
did not receive this medication.
While this study concentrated on prostate surgery, the concept
can be utilized for other types of surgery as well. Way back in
February 1996, pre-emptive analgesia was found to lessen pain
in arthroscopic knee surgery. In that
study, not only was pre-emptive analgesia shown to result
in less pain after the operation but it was also shown that the
patients that were given pre-emptive analgesia
required less narcotic pain medicine.
Interestingly, a group of researchers reported in 1998 that
giving the patient some ibuprofen before the surgery may be as
effective as giving an intravenous dose of a stronger and more
expensive medication called ketorolac (Mixter CG III, Meeker LD,
Gavin TJ. Preemptive pain control in patients having laparoscopic
hernia repair: a comparison of ketorolac and ibuprofen. Arch Surg.
1998;133:432-437). This implies that simple
and cheap methods of pre-emptive analgesia might be available
- and that not only expensive, complicated methods are effective.
Similarly, the injection of a small dose of local anesthetic
directly into the incision site before a laparoscopic procedure
can reduce post-operative pain and the need for pain medication
- this according to a study presented at the annual meeting of
the American College of Obstetricians and Gynecologists in 1998.
Raymond Ke, M.D., an assistant professor of obstetrics and gynecology
at the University of Tennessee in Memphis reported that patients
in the pre-emptive analgesia group were able to wait longer after
surgery before taking their first dose of pain medicine compared
with patients not receiving pre-emptive analgesia. In addition,
lower pain scores were reported at all time intervals in the pre-emptive
analgesia group.
These studies, and others like them, suggest that there are simple, easy and cost-effective methods that
can be utilized to reduce pain in surgical patients.
While there are more studies that should be done and there are
still some doctors that don't fully agree with this method, more
and more results are coming out each year that suggest it is a
safe, effective and desirable part of the anesthetic plan
for pain control. Through this method, anesthesiologists
can have an important impact on their patients beyond the operating
room - well in to recovery and even once the patient has returned
home.
Now, it is important to realize that while these methods may
reduce pain, they cannot eliminate it all together. Most patients
will still need medications for pain after surgery. Many patients
after surgery have inadequate pain relief because they try to
avoid taking pain medications, waiting until the pain is unbearable
before turning to injections or pills. Remember, it is far easier
to prevent pain than to stop it and pain sensitizes nerves to
react more the next time- so it is far better to take pain medication
according to the prescribed schedule, at least early on in the
recovery process, rather than waiting for the pain to come.. In
addition, pain prevents patients from doing things that are important
to recovery - breathing, walking, eating, etc. Don't assume that
suffering is an essential part of recovery or that the pain somehow
"builds character". Take advantage of what we have
learned and stop pain before it starts.
If you are interested in reading further, here is a bibliography of some pertinent articles.
email: contact@anesthesiologyinfo.com
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