Postoperative pain may increase risk of temporary problems with learning, memory

November 6, 2013, Massachusetts General Hospital

The pain caused by a surgical incision may contribute to the risk of postoperative cognitive dysfunction, a sometimes transient impairment in learning and memory that affects a small but significant number of patients in the days following a surgical procedure. An animal study from Massachusetts General Hospital (MGH) researchers, appearing in the November 6 Journal of Neuroscience, also identifies a probable mechanism for pain-induced cognitive impairment, suggesting pathways that may be targeted by potential preventive measures.

"These findings suggest, for the first time, that is one of the perioperative factors that contribute to the risk of cognitive dysfunction in surgical patients – in addition to the surgery itself, anesthetics, sleep disturbance and other factors," says Zhongcong Xie, MD, PhD, director of the Geriatric Anesthesia Research Unit in the MGH Department of Anesthesia, Critical Care and Pain Medicine. "While postoperative cognitive dysfunction may be temporary, it still can have a major impact on the quality of life of patients and their caregivers at a time when patients' ability to participate in their own care is very important."

Up to 80 percent of surgical patients in the U.S. have some level of postoperative pain, and several studies have suggested that pain could contribute to the development of postoperative cognitive dysfunction. To investigate the potential connection, Xie's team conducted a number of experiments with a group of mice that had small incisions made on one of their paws under general anesthesia. At 1, 3 and 7 days after the procedure, the animals were tested to see how sensitive the affected foot was to discomfort. The animals showed increased sensitivity to pressure with a nylon filament in the area of the incision on days 1 and 3 but not day 7.

Several standard tests of learning and memory revealed that, compared with a group of mice that underwent a sham procedure involving no incision, the animals that received an incision had impaired performance on particular tasks at day 3 and 7 but not on day 30. The animals' ability to remember tasks learned before the incision was not affected, but their performance on certain new tasks was diminished.

While pain-associated was seen in animals that could be considered middle-aged, young adult animals exhibited little cognitive dysfunction despite showing postoperative discomfort. A group of mice with incisions that were subsequently treated with local anesthetic did not show either the increased level of discomfort or the extent of cognitive impairment that was seen in the other incision-treated mice, implying that the and not the incision itself contributed to the dysfunction.

Previous research has indicated that a molecule called the NMDA receptor 2B (NR2B), present on several types of brain cells, is involved with pain perception as well as learning and memory. The team's analysis of brain tissues of animals in this study revealed that those with incision-related pain also had decreased NR2B expression in neuronal synapses within particular brain structures involved in learning and memory. Further investigation suggested that reduced synaptic NR2B expression was a consequence of increased levels of the inflammatory cytokine TNF-alpha and the neuronal enzyme CDK5, which is known to regulate NR2B expression.

"Our findings suggest that inadequate pain treatment may lead to postoperative cognitive dysfunction through a synapse-associated mechanism," Xie says. "Along with improved pain control, treatments that target inflammation and CDK5 activity could also mitigate the problem. We hope this research will promote more studies into the underlying mechanism of postoperative – specifically whether aged animals have greater pain-associated postoperative impairment – findings of which should ultimately improve outcomes for ." Xie is an associate professor of Anesthesia at Harvard Medical School.

Explore further: Study reveals how anesthetic isoflurane induces Alzheimer's-like changes in mammalian brains

Related Stories

Study reveals how anesthetic isoflurane induces Alzheimer's-like changes in mammalian brains

March 1, 2012
The association of the inhaled anesthetic isoflurane with Alzheimer's-disease-like changes in mammalian brains may by caused by the drug's effects on mitochondria, the structures in which most cellular energy is produced. ...

Neuroinflammation may be behind general-anesthesia-associated learning disabilities

January 24, 2013
Several studies have found evidence that children who undergo repeated surgical operations with general anesthesia before the age of 4 may be at an increased risk for learning disabilities. In the March issue of Anesthesiology, ...

Epidural during/Post spine surgery gives better outcomes

July 17, 2013
(HealthDay)—In patients undergoing reconstructive spine surgery, combined epidural and general anesthesia results in better pain control and other outcomes compared with general anesthesia plus narcotics, according to a ...

Surgeons report two new approaches to lessen postoperative pain

October 8, 2013
New combinations of postoperative pain treatment decreased both pain and the use of narcotic pain relievers according to two studies presented this week at the 2013 Clinical Congress of the American College of Surgeons. One ...

Pleasure and pain brain signals disrupted in fibromyalgia patients

November 5, 2013
New research indicates that a disruption of brain signals for reward and punishment contributes to increased pain sensitivity, known as hyperalgesia, in fibromyalgia patients. Results published in Arthritis & Rheumatism, ...

Aspirin-triggered resolvin protects against cognitive decline after surgery

May 27, 2013
(Medical Xpress)—Resolvins are molecules naturally produced by the body from omega-3 fatty acids - a process that can be jumpstarted by common aspirin. In a new study, published in The FASEB Journal, researchers at Karolinska ...

Recommended for you

Electrical implant reduces 'invisible' symptoms of man's spinal cord injury

February 19, 2018
An experimental treatment that sends electrical currents through the spinal cord has improved "invisible" yet debilitating side effects for a B.C. man with a spinal cord injury.

To sleep, perchance to forget

February 17, 2018
The debate in sleep science has gone on for a generation. People and other animals sicken and die if they are deprived of sleep, but why is sleep so essential?

Lab-grown human cerebellar cells yield clues to autism

February 16, 2018
Increasing evidence has linked autism spectrum disorder (ASD) with dysfunction of the brain's cerebellum, but the details have been unclear. In a new study, researchers at Boston Children's Hospital used stem cell technology ...

Fragile X syndrome neurons can be restored, study shows

February 16, 2018
Fragile X syndrome is the most frequent cause of intellectual disability in males, affecting one out of every 3,600 boys born. The syndrome can also cause autistic traits, such as social and communication deficits, as well ...

Brain-machine interface study suggests how brains prepare for action

February 16, 2018
Somewhere right now in Pyeongchang, South Korea, an Olympic skier is thinking through the twists and spins she'll make in the aerial competition, a speed skater is visualizing how he'll sneak past a competitor on the inside ...

Humans blink strategically in response to environmental demands

February 16, 2018
If a brief event in our surroundings is about to happen, it is probably better not to blink during that moment. A team of researchers at the Centre for Cognitive Science from Technische Universität Darmstadt published a ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.