Leaky sutures after abdominal surgery are a potentially life-threatening complication that surgeons may not notice right away. Researchers have now developed a hydrogel patch that not only aids in wound closure but also rapidly detects leaks at abdominal suture sites.
For example, when a surgeon removes a section of bowel and sews the ends together (a so-called anastomosis), it can leak. The problem is that once the skin is closed, the surgeon may not know if there is a leak in the abdominal cavity.
An anastomotic leak can cause highly acidic gastric juices to spill into the abdominal cavity and can lead to serious complications such as inflammation and infection of the tissues in the cavity (peritonitis) and life-threatening blood infection (sepsis). Leaks are usually only discovered when patients develop symptoms such as pain and fever and their overall health deteriorates.
The problem with developing a device that aids in the closure of an anastomotic stoma or monitors its leakage is that it must be able to withstand the high acidity of gastrointestinal fluids without damage. Now, researchers from the Swiss Federal Laboratory for Materials Science and Technology (Empa) and ETH Zurich have developed a leak detection patch that can withstand the acidic environment of the gut and also help to close wounds.
“Surgeons tell us that even in the most complex surgeries they keep an eye on the operating area – but once the abdominal cavity is closed they are ‘blind’ and may not notice the leak until it is too late,” says Alexandre Anthis , one of the corresponding authors of the study.
The patch consists of a layered hydrogel matrix embedded with carbonates (barium or lanthanum) and serves as a non-electronic sensor. Barium carbonate has been widely used as an X-ray contrast agent, while lanthanum carbonate is used to reduce high blood phosphorus levels caused by kidney disease.
When the carbonate comes into contact with acidic digestive fluids, it breaks down, producing carbon dioxide bubbles that remain trapped in the hydrogel matrix. Bubbles can be seen using ultrasound because they stand out from the surrounding tissue due to their high contrast.
As a “backup” leak detection mechanism, the patch also changes shape in the presence of digestive fluids — becoming rings or threads — making it easy to spot with computed tomography (CT) scans. This means the patch provides “dual mode” sensing, with leaks visible on both ultrasound and CT, including ultra-low dose CT.
“In the future, a sensor with a shape that clearly stands out from the anatomy in CT and ultrasound images could reduce ambiguity in the diagnosis of impending leaks,” said Inge Herrmann, co-corresponding author of the study.
The researchers tested their patch in a piglet model and found that the two carbonates only responded to the acidic conditions associated with exposure to gastric fluid, making false positives less likely. Depending on the size of the leak, the reaction from contact with stomach acid can occur within minutes or hours. Often, healthcare professionals must rely on leaking clinical signs, which can take a while to manifest.
What’s more, the carbonate sensor is encapsulated in polyacrylamide, a water-absorbing polymer that allows the patch to firmly adhere to the wound site, sealing the wound while preventing it from moving. This could reduce the risk of complications and length of hospital stay after abdominal surgery, the researchers said.
While further research is needed to determine the long-term fate of their wound-supporting sensor patch, the researchers say their device offers a cost-effective way to quickly detect leaks, allowing for timely treatment.
“The gut patch project has generated a lot of interest in the medical community,” Herrmann said.
The study was published in the journal advanced science The following video, produced by Empa, outlines the advantages of leak detection patches.
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