Now Stanford University researchers have discovered that right after surgery, patients' blood harbours clues about how fast they'll bounce back — and it has to do with the activity of certain immune cells that play a key role in healing.
The work one day may lead to a test to predict who'll need more care, or maybe even if an operation is the best choice.
"We could ask, 'Are you fit for surgery?'" said Dr. Martin Angst, a Stanford professor of anesthesiology and perioperative medicine, who helped lead the research published Wednesday.
U.S. doctors perform millions of operations every year, many of them minor but others much more complex. Speed of recovery depends in part on the type of surgery and how sick the person is. Some hospitals have begun implementing "enhanced recovery" strategies, specific steps to take right before and after certain major operations in hopes of at least speeding the patient's discharge from the hospital, if not their overall recuperation time.
But scientists don't know what biology explains why some people recover so much faster than someone else who's equally sick, information that could help guide development of those enhanced-recovery programs.
"I'm very excited that the science around surgery recovery is going that direction," said Dr. Julie Thacker, a colorectal surgeon at Duke University who wasn't involved in the new study but praised the work.
Thacker has helped implement an enhanced-recovery program at Duke that she said works well, but said she can't explain which steps are most important or why without research into how they affect such things as the body's inflammatory response.
The Stanford team took an unusually close look at 32 otherwise fairly healthy people who underwent a first-time hip replacement. They took blood samples from the patients before surgery and at several points afterward, and questioned them pain, fatigue and other elements of recovery every few days for six weeks.
That recovery was quite varied: Some experienced only mild pain just two days after surgery, while others didn't report their pain was mostly gone until 36 days later. The median time to recuperate from post-surgical fatigue, extreme tiredness after simple activity, was three weeks, meaning half of patients fared better and half took longer.
To learn why, the researchers looked to immune cells that are behind the inflammation that always occurs with a wound. To find and map the activity of key players, they turned to the lab of Stanford immunology professor Garry Nolan, who helped develop a technology that measures dozens of features of individual immune cells simultaneously.
The discovery: Patients' blood shows an immune signature of recovery that accounts for much of their variability in recovery time — a pattern of activity in certain immune cells that are first responders to the injury site, the researchers reported Wednesday in the journal Science Translational Medicine.
If that particular reaction is controlled in the first 24 hours after surgery, patients recover faster. But when that reaction increases instead, patients recover more slowly, Angst said.
"We were surprised," that such an early reaction set the stage for recovery, he said.
But it makes sense, he added: Inflammatory processes initiate healing but "you have to keep them on a leash and dwindle down efforts," because too much inflammation harms.
The team has begun a larger study to see if the results hold up, and plans to study whether the same kind of immune reaction may play a role in other kinds of surgery, such as abdominal operations.
The ultimate goals are to create a simple blood test that could tell who is more likely to experience a protracted recovery — right after surgery or maybe even before — and to hunt treatments that might alter the immune reaction to help.
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