Trauma patients likely to experience moderately severe pain 1 year after injuries

Trauma patients likely to experience moderately severe pain 1 year after injuries
Frederick P. Rivara, M.D., M.P.H., et al
Most patients have moderately severe pain resulting from their injuries one year after sustaining major trauma, according to a report in the March issue of Archives of Surgery, one of the JAMA/Archives journals.

“Pain is a natural accompaniment of acute injury to tissues and is expected in the setting of acute trauma,” according to background information in the article. Recent studies have shown that most patients with pelvic fractures and lower extremity injuries continue to experience chronic pain five to seven years after injury. Pain after injury can lead to disability, post-traumatic stress disorder and depression.

Frederick P. Rivara, M.D., M.P.H., of the University of Washington, Seattle, and colleagues analyzed information from 3,047 patients (age 18 to 84) who were admitted to the hospital and survived to one year after experiencing acute trauma. Pain 12 months after injury was measured on a 10-point scale. Personal, injury and treatment factors that may predict chronic pain in these patients were also noted.

“At 12 months after injury, 62.7 percent of patients reported injury-related pain. Most patients had pain in more than one body region, and the mean [average] severity of pain in the last month was 5.5 on a 10-point scale,” the authors write. The occurrence of pain one year after injury was most common in those age 35 to 44 and least common in those 75 to 84. “The most common painful areas were joints and extremities (44.3 percent), back (26.2 percent), head (11.5 percent), neck (6.9 percent), abdomen (4.4 percent), chest (3.8 percent) and face (2.8 percent).”

Most (59.3 percent) of those with injury-related pain had three or more painful areas one year after injury, while only 37.3 percent had a single painful area. Patients age 75 to 84 had the fewest number of injury-related painful areas, while those 35 to 44 had the most.

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Conquering chronic pain: scientists find a key

Scientists have found a substance that, in mice, blocks chronic pain but does not appear to cause any of the unwanted side effects of existing painkillers, according to a study released on Wednesday.

Researchers led by Hanns Zeilhofer at the University of Zurich in Switzerland found the compound after exploring the way pain signals travel up to the brain via the spinal cord.

"Normally the spinal cord acts as a kind of filter, ensuring that not all painful signals coming from the periphery of the body reach the brain," Zeilhofer told AFP in an interview.

If these neurological gatekeepers were totally absent, even the lightest touch on the skin would make us wince with discomfort, he explained. "We would be in constant pain without them."

But in patients with chronic pain, this filter function is impaired, meaning that the spinal cord is like an open channel for pain signals, he said.

A key role in the inhibition process is played by two nervous-system chemicals, called neurotransmitters.

One is gamma-aminobutyric acid, also known as GABA, and the other is glycin.

"We thought we could restore the filter function if we pharmacologically enhance the action of GABA or glycin in the spinal cord," said Zeilhofer.

But as no compounds had been developed that target glycin, they focused instead on GABA.

In experiments reported in the British journal Nature, the researchers induced inflammation in the paws of mice and rats, and then gauged the force needed to make the animal withdraw its leg, creating a rough measure of pain.

First they injected Valium into the spinal cord. As predicted, the drug increased the transmission of GABA, significantly reducing the rodents’ aversive reactions.

But the problem with Valium as a treatment for pain is that it also causes drowsiness, impairs memory formation and rapidly loses its effectiveness, said Zeilhofer.

All these unwanted side-effects occur in the brain, he noted, so he and his team wondered if there wasn’t another chemical that would act only on the spinal cord.

That’s when they found L-838,417, a compound that suppressed the pain signals without causing sedation or losing its effectiveness over time.

"During a nine-day treatment in rats, we found the morphine completely lost its analgesic effect, whereas the analgesic effect of L-838,417 was completely retained," Zeilhofer said.

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