Study determines how to give post-op pain relief to opioid-tolerant patients

[Guest guest]

Public release date: 27-Apr-2004

Contact: Phil Sahm

801-581-2517

University of Utah Health Sciences Center

Univeristy of Utah anesthesiologists on front lines in battle against

post-operative pain

Study determines how to give post-op pain relief to opioid-tolerant patients

SALT LAKE CITY -- Post-operative pain is the No. 1 issue for people who've

had surgery-and University of Utah anesthesiologists are helping these

patients fight that battle on several fronts.

Anesthesiologists at the U School of Medicine and hospital have developed a

way to determine precisely how much medication is needed to relieve pain in

major surgery patients who've become tolerant to opioids-the primary drugs

used to relieve post-operative pain. The U physicians just won the top award

for their presentation on pain control at the International Anesthesia

Research Society meeting in Tampa, Fla

They're also using two new techniques that not only alleviate post-operative

pain but also shorten the hospital stays for people who've had total knee

replacements, surgery on their anterior cruciate ligaments (ACL), or who've

experienced fractures or other injuries of the lower extremities.

University Hospitals & Clinics is the only hospital in Utah using these

breakthrough techniques.

As millions of Americans take Lortab, OxyContin, and other narcotics to

relieve chronic pain, the daily prescriptions of those drugs are making it

harder to get effective pain management after they've had major surgery.

That's because people who take daily prescription narcotics develop a

tolerance to opioids. This has made recovery from major surgery more painful

for these patients because standard post-operative doses of morphine haven't

worked-until now.

U of U anesthesiologists have developed a method that takes into account a

patient's opioid tolerance and helps physicians determine the right amount

of medication to stop post-operative pain in people who already take a daily

narcotic prescription.

Opioid tolerance affects hundreds of patients who have surgery at University

Hospitals & Clinics, according to anesthesiologists D. Swenson,

M.D., associate professor, and J. , M.D., assistant professor,

at the U School of Medicine and lead authors of the paper.

" Compared to five years ago, there's a huge number of people coming into the

hospital already taking narcotics, " Swenson said. " You give them medication

and, unfortunately, it doesn't touch the pain. "

Swenson and other U anesthesiologists studied 20 opioid-tolerant patients

undergoing back surgery and who received the pain medication fentanyl

immediately prior to their operations. Fentanyl is a synthetic opioid used

for pain control that is 100 times more potent than morphine.

As each patient was anesthetized, he or she received fentanyl until

respiratory depression was induced. When respiratory depression had been

reached, each patient then underwent general anesthesia. Using software

developed at Stanford University-but modified by U anesthesiologists Talmage

D. Egan, M.D., professor, and Kenward B. , M.D., associate

professor-the concentration of fentanyl associated with respiratory

depression was determined for each patient.

Once the U anesthesiologists determined the fentanyl dose associated with

respiratory depression in each patient, the software helped them calculate

how much of the drug was needed for pain relief. By testing each

individual's response to fentanyl, the anesthesiologist was able to predict

a safe and effective dose of opioid that was " tailor made " for each patient.

They found that the amount of fentanyl needed to cause respiratory

depression in the opioid tolerant study subjects averaged 20.74 nanograms

per milliliter. The amount needed for adequate pain relief averaged 7.07

nanograms per milliliter. Both measurements were substantially higher than

for people who are not opioid-tolerant.

The fentanyl dose required for pain relief among the individual patients

varied from 2.1 nanograms per milliliter to 22.3 nanograms per milliliter.

In other words, some patients required 10 times as much fentanyl for pain

relief.

" That means standard doses of opioids could be as much as 10 times lower

than some patients need for adequate pain relief, " Swenson said.

This method has become the standard protocol at University Hospital and U

anesthesiologists are using it 10-15 times a month for opioid-tolerant

patients who undergo surgery.

Along with Swenson, , Egan, and , other contributors to the

study included D. Dillon, M.D., and medical student H. Hall.

U anesthesiologists also are using a new method to control post-op pain in

40-60 people who undergo knee surgery every month at University Hospital.

A fascia iliaca catheter, also called a femoral block, often is used to

control pain following knee replacement and ACL surgery. But instead of

placing the catheter right next to the nerve to administer local anesthetic,

which is the most common way of doing it, U of U anesthesiologists insert

the catheter in a space near the nerve without touching it. Then they bathe

the nerve in a local anesthetic, and the results for pain control have been

dramatic.

Patients given a femoral block after surgery go home from the hospital a

full day sooner because of the pain relief. They're also able to take pills

instead of receiving pain medication intravenously.

Employing a similar method, U anesthesiologists use a sciatic nerve catheter

for patients who have ankle fractures or other injuries below the knee, and

the results have been equally impressive, according to Swenson. This

technique has allowed patients who might otherwise be hospitalized for 3-4

days because of severe pain to go home with the catheter in place the day

after surgery.

Between 20 and 30 surgery patients are given the sciatic nerve catheter at

University Hospital each month, Swenson said.