The Core Component: Bentonite Clay
At the heart of Hemospray's technology is its main ingredient: a proprietary blend of purified bentonite clay. Bentonite is a highly absorptive, naturally occurring mineral clay that is inert and non-toxic. It contains no human or animal proteins, botanicals, or known allergens, making it a safe option for many patients. This makes it a significant development in medical care, particularly for managing gastrointestinal bleeding, as it minimizes the risks associated with tissue reaction and allergic response from biological agents. The powder itself is referred to as TC-325 during development and in clinical literature.
Mechanism of Action: How Bentonite Stops Bleeding
The hemostatic effect of Hemospray is achieved through a two-fold, non-pharmacological mechanism of action, leveraging the natural properties of bentonite clay.
Mechanical Tamponade
When the TC-325 powder is sprayed onto an actively bleeding site, it rapidly absorbs the water content from the blood and other fluids. This absorption process causes the mineral powder to swell and form a cohesive, adhesive hydrogel matrix that coats the bleeding tissue. This gelled matrix creates a stable mechanical barrier that exerts pressure on the bleeding site, a process known as mechanical tamponade, effectively sealing the source of the hemorrhage. The non-contact application of the spray minimizes further trauma to fragile or friable tissue, a major advantage over traditional contact-based therapies.
Concentration of Clotting Factors
In addition to the mechanical barrier effect, the rapid absorption of fluid by the bentonite powder helps to concentrate platelets and other coagulation factors at the bleeding site. By drawing water out of the blood, the powder effectively increases the local concentration of the body's natural clotting components, enhancing the coagulation cascade and accelerating the formation of a stable blood clot. This dual action allows for rapid hemostasis, even in challenging situations like diffuse or hard-to-reach bleeding, or in patients with coagulopathies.
Delivery and Application Process
The application of Hemospray requires a specific delivery system and is conducted endoscopically.
Here's how the process works:
- An endoscope is inserted into the gastrointestinal tract to locate the bleeding site.
- A specialized catheter is passed through the working channel of the endoscope to the area of bleeding.
- The Hemospray canister, which contains the TC-325 powder and is powered by a compressed carbon dioxide (CO2) propellant, is attached to the catheter.
- The clinician delivers short, controlled bursts of the powder to spray and cover the entire bleeding area.
- The inert powder is then sloughed off the mucosa and passed naturally through the GI tract over the next few days.
Comparison of Hemostatic Agents
Hemospray stands apart from other hemostatic methods in several key ways, including its application technique and mechanism.
| Feature | Hemospray (TC-325) | Conventional Endoscopic Therapy (Clips, Cautery) | Other Hemostatic Powders (e.g., EndoClot) |
|---|---|---|---|
| Primary Mechanism | Mechanical barrier (tamponade) and concentration of clotting factors | Mechanical occlusion or thermal coagulation | Forms a gelled matrix, concentrates clotting factors |
| Main Ingredient | Inert mineral powder (bentonite clay) | Metal (clips), electricity/heat (cautery) | Polysaccharides from plant starch |
| Application | Non-contact, sprayed over bleeding site | Requires direct contact and precise targeting | Non-contact, sprayed over bleeding site |
| Best for Bleeding Type | Diffuse, difficult-to-target, or friable bleeding | Punctate sources, visible vessels | Prophylactic use or oozing bleeding |
| Key Advantage | Covers large areas quickly, reduces trauma | Definitive therapy for targeted lesions | Provides durable, prolonged adherence |
| Key Limitation | High rebleeding rates as monotherapy | Technically challenging for diffuse bleeds | Different indications and regulatory status |
Safety Profile and Efficacy
Numerous studies have demonstrated the efficacy of Hemospray, particularly for achieving immediate hemostasis in cases of gastrointestinal bleeding. However, it is important to note that due to relatively high rates of re-bleeding, Hemospray is often used as a bridging therapy or in combination with other methods, rather than as a definitive long-term solution.
- High Initial Success: Research indicates a high rate of immediate bleeding control, with reported success rates often exceeding 90%.
- Effective for Challenging Cases: Its non-contact, broad application is particularly useful for controlling bleeding from tumors or friable tissue where direct contact is risky.
- Safety Concerns: While generally safe, rare adverse events have been reported, such as bowel perforation in approximately 1% of patients. Concerns regarding gas embolism are also noted, particularly in specific settings like variceal bleeding, though evidence suggests a low risk.
Advantages and Limitations of Hemospray
Advantages
- Non-Contact and Nontraumatic: The aerosol delivery system avoids direct contact, making it ideal for fragile tissues or sites that are difficult to access directly.
- Rapid Application: It can be applied quickly and effectively over large, diffuse areas of bleeding.
- Effective Rescue Therapy: It is highly effective as a rescue option when conventional hemostatic techniques fail to control bleeding.
- Broad Indication: Used for a wide variety of non-variceal upper and lower GI bleeding.
- Versatility: It can be used as a monotherapy, as a first-line therapy, or in combination with other techniques.
Limitations
- Risk of Rebleeding: The rate of re-bleeding is a significant concern, making it less suitable as a standalone, definitive therapy in many cases.
- Obstruction of View: The powder can obscure the endoscopic view, temporarily hindering the procedure.
- Clogging Risk: Catheter blockage can occur if the device is not used with a completely dry catheter.
- Specific Contraindications: It is not approved for all types of bleeding, particularly variceal bleeding due to gas embolism concerns.
Conclusion
In summary, Hemospray's efficacy as an endoscopic hemostatic agent is fundamentally tied to its composition. The non-toxic, inert bentonite clay powder allows it to form a physical barrier and concentrate clotting factors upon contact with blood, providing rapid, non-contact hemostasis. While it has revolutionized the treatment of acute and diffuse gastrointestinal bleeding, particularly in difficult-to-treat cases, its primary role is often as a bridging therapy rather than a permanent solution due to the risk of rebleeding. Understanding what is Hemospray made of is key to appreciating its unique mechanical action and appropriate application within endoscopic medicine.
