The millions of people who undergo major surgery each year have no way of knowing how long it will take them to recover from their operations. Some will feel better within days. Others won’t for a month or more. Right now, doctors can’t tell individual patients which category they’ll fit into.
But Stanford researchers have discovered that the activity level of a small set of immune cells during the first 24 hours after surgery provides hints about how quickly patients will bounce back from surgery-induced fatigue and pain, and be back on their feet again.
“We learned that within the first 24 hours after surgery you can find strong clues in blood that reveal what shape a particular patient is going to be in two weeks later,” says Martin Angst, MD, professor of anesthesiology, pain and perioperative medicine, who shared senior co-authorship of the study with microbiology and immunology professor Garry Nolan, PhD.
The discovery could lead to the development of a blood test for predicting recovery after major surgery. Such a test could both help physicians optimize recovery regimens and let patients know what to expect. A full understanding of the molecular mechanisms identified in the study might even make it possible for clinicians to manipulate the immune system to foster faster recoveries.
In the study, published in Science Translational Medicine, the researchers analyzed blood samples drawn from 32 middle-aged to older patients undergoing a hip-replacement procedure. The highly sensitive technology used for the analysis — single-cell mass cytometry — simultaneously monitors large numbers of biochemical features on the surfaces of immune cells and within the cells. The researchers drew blood from the patients one hour before surgery, then at one, 24 and 72 hours post-surgery and again four to six weeks after surgery. They used the cytometery device, developed in Nolan’s lab, to determine the identities and activities of the immune cells the samples contained. The Stanford team observed what Angst calls “a very well-orchestrated, cell-type- and time-specific pattern of immune response to surgery.” The pattern consisted of a sequence of coordinated rises and falls in numbers of diverse immune-cell types, along with various changes in activity within each cell type.
“Amazingly, this post-surgical signature showed up in every single patient,” Angst says. However, the magnitude of the various increases and decreases in cell numbers and activity varied from one patient to the next. In particular, activity patterns in one fairly rare subset of immune cells correlated strongly with patients’ recovery times.
The Stanford group is now looking to see if they can identify a pre-operation immune signature that predicts the rate of recovery. That could help clinicians decide when, or if, a patient should have surgery.