CONTACT: JENNIFER CRONIN
2130 Medical Laboratories
Iowa City IA 52242
(319) 335-5661; fax (319) 335-9917
UI researcher unraveling mechanisms for postoperative pain
IOWA CITY, Iowa -- Imagine having an operation and recuperating without
the usual discomfort or even being pain-free after surgery.
Sound impossible? Maybe not.
But before researchers can find ways to minimize or eliminate the painful
aftereffects of surgery, they first must understand how incisions cause
pain. A University of Iowa researcher is taking the once sore subject that
has evaded scientists and is beginning to unravel it.
While pain research has expanded greatly over the last 15 years, few
investigators really have focused on surgical incision pain even though
it is a common, costly and poorly understood form of acute pain. Some 80
to 90 percent of surgical procedures involve some type of discomfort, said
Timothy Brennan, M.D., Ph.D., UI associate professor of anesthesia. The
worst pain is after thoracotomies, total knee replacements and major abdominal
"Postoperative pain is an unrecognized pain problem from a basic
science point of view," Brennan said.
Basic research has concentrated on pain signaling pathways. More recently,
mechanisms for hypersensitivity or exaggerated response phenomena after
injury have been emphasized, Brennan said. Injury from incisions in postoperative
patients is a common cause of hypersensitivity, and for Brennan, an anesthesiologist
with a background in pain research, postoperative incision-induced pain
became an obvious problem that needed to be addressed from a basic science
"Not only is surgery the most common cause of acute pain, but finding
ways to reduce pain or stop it completely will improve patient satisfaction,
reduce morbidity and perhaps decrease mortality following surgery,"
said Brennan, who has been looking at postoperative pain for the last five
Brennan has developed an animal model to investigate postoperative pain
and hopes that his work eventually leads to intraoperative and postoperative
pain management changes for patients. So far, Brennan and his colleagues
have found a group of spinal neurotransmitter receptors that may be key
in transmitting the hypersensitivity that incisions cause. Brennan anticipates
new drug discoveries that block these particular excitatory amino acid
neurotransmitter receptors may greatly reduce or eliminate some patients'
Brennan also has described which particular groups of neurons in the
spinal cord become activated and sensitized by a surgical incision and
thus transmit postoperative pain.
"We will continue to search for the pathways that become sensitized
by incisions," Brennan said. "As we characterize the responses
of the nerves, potential new therapeutics should follow."
The medical community currently treats most postoperative pain with
opioids; however, studies have shown that drugs like morphine do not greatly
reduce post-surgical pain induced by activities as simple as deep breathing,
coughing or walking, Brennan said. Plus, there are side effects: nausea
and vomiting, delayed gastric emptying and prolonged recovery of bowel
Pharmaceutical companies, as well as other basic science laboratories,
are taking notice of Brennan's model and the results learned from it.
"We anticipate a strong effort by a number of groups to try to
solve this puzzle, and in the future, we hope to eliminate the problem,"
New drugs for postoperative pain currently are undergoing trials, said
Brennan, who expects trials to escalate in the next five years.