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Gastric fluid responsive sensor system enables early and robust detection of postoperative leaks

Researchers ETH Zurich, Zürich, Switzerland, have developed a gastric leak sensor system that facilitates the early and robust detection of postoperative complications after bariatric surgery. The system is enabled by a gastric fluid responsive, dual modality, electronic-free, leak sensor system integrable into surgical adhesive suture materials.

The leak sensors contain high atomic number carbonates embedded in a polyacrylamide matrix, that upon exposure to gastric fluid convert into gaseous carbon dioxide (CO2). These CO2 bubbles remain in the hydrogel matrix, leading to a distinctly increased echogenic contrast detectable by a low-cost and portable ultrasound transducer, while the dissolution of the carbonate Gastric fluid responsive sensor system enables early and robust detection of postoperative leaks species and the resulting diffusion of the cation produces a markedly reduced contrast in computed tomography (CT) imaging.

According to the researchers, the utilisation of CT and ultrasound allows for frequent patient screening, a key feature essential for rapid leak detection and optimal opportunity for timely treatment. Furthermore, both imaging modalities are fully established in the everyday clinical practice, considerably facilitating the clinical translation of the presented gastric leak sensors and opening new routes for postoperative patient surveillance using existing hospital infrastructure. The findings were reported in the paper, ‘Surgical Sealant with Integrated Shape-Morphing Dual Modality Ultrasound and Computed Tomography Sensors for Gastric Leak Detection’, published in the journal Advance Science.

Although rare, anastomotic leaks are major and potentially fatal complication from surgery and are currently only detectable once the patient develops clinical symptoms. Now, the Swiss investigators have developed a novel adhesion acid sensitive hydrogel makes it possible to detect dangerous leaks before they cause damage.

“Currently, it is extremely challenging for healthcare professionals to identify these types of leaks early. They are mostly diagnosed based on clinical symptoms occurring as a result of a fully developed leak,” said Inge Hermann, a researcher at ETH Zurich, in Switzerland whose team has worked to develop a new leak sensor. “This means that, at that time, the patient is already at high risk of developing life-threatening sepsis. Our technology offers a potential route to early detection as it can alert doctors before leaks become clinically symptomatic.”

Firstly, Hermann and colleagues designed a sensor that would be responsive to leaking gastric fluids. They identified two carbonate salts, barium and lanthanum carbonates, that decompose in the presence of acidic stomach juices to release carbon dioxide gas. These gases are trapped within a layered hydrogel that can be used to seal a surgical site. The dissolved carbon dioxide gas alters the speed of sound within the sealant, which in turn makes the leak visible as a brighter spot during an ultrasound. Simultaneously, the positive ions diffusing out of the sensor lead to lower contrast and a darker spot in a CT scan.

After identifying the best sensor materials, the researchers subjected them to various leak and non-leak scenarios in the context of different physiological conditions to test their sensitivity, specificity and safety.

Once these basics had been established, the researchers tested the sensor sealant in multiple settings. In one test, the team placed the surgical sealant and sensor on the outermost layer of a porcine stomach as a surgical patch. When exposed to gastric fluid, the sensors responded, and a leak was recorded using both ultrasound and CT.

In order to make detection easier, the researchers also tested different configurations - circular or linear - of the sensors. For instance, when placed as two concentric circles, the salts would appear as a solid circle in the absence of a leak. But in the presence of gastric acid, the outer circle would break down into carbon dioxide, leaving behind a detectable ring during imaging.

The team has tested the surgical sealant in an animal model. The sealant was applied to both wound and normal sites on stomach tissue. At multiple timepoints post-surgery, the researchers captured CT images. When placed on a leaking connection the shape of the sensor changed three hours after surgery, and a more distinct difference after six hours with both ultrasound and CT images was observed. On the other hand, the sealant patch placed on normal tissue remained unchanged.

“The integration of these sensing elements into surgical sealants paves the road for leak detection prior to gastric fluid escape into the abdominal cavity, a phenomenon which otherwise greatly complicates treatment and carries substantial risks for the patient,” the researchers concluded. “We demonstrate patterning and geometric morphing of sensing elements under leak conditions for straightforward identification in medical images by the naked eye, as well as setting of the blueprint for artificial intelligence-assisted recognition of impending leaks.”

Next, the researchers intend to test their device in experimental settings that more closely mimic patient experiences.

To access this paper, please click here


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