The Components of the Foam Sclerotherapy Mixture
Foam sclerotherapy harnesses the power of a specially prepared mixture to treat damaged veins. This formulation consists of two primary components: a sclerosing agent and a gas. Understanding each part is crucial to grasping why the foam is so effective.
Detergent Sclerosants
The active ingredient in the mixture is a detergent-based sclerosing agent. These substances are specifically formulated to cause localized chemical irritation to the endothelium, the inner lining of the vein. This irritation triggers a chain of events that leads to fibrosis and eventual collapse of the vessel. The two most commonly used detergent sclerosants are:
- Polidocanol (Aethoxysklerol®): A non-ionic detergent and a local anesthetic, polidocanol is widely used and available in various concentrations (e.g., 0.25%, 0.5%, 1%, 2%, 3%). For foam sclerotherapy, higher concentrations may be used for larger veins.
- Sodium Tetradecyl Sulfate (STS) (Sotradecol®): This synthetic, long-chain fatty acid is another staple of sclerotherapy. It is available in 1% and 3% concentrations and can be diluted with saline to achieve the desired strength.
Both agents work by disrupting the cell surface lipids and removing proteins, causing the vessel walls to scar and close.
The Gas Component
The gas component is what transforms the liquid sclerosant into a foam. The choice of gas can affect the foam's stability and characteristics, but for most clinical applications, either room air or a physiological gas mixture is used.
- Room Air: This is the most common and accessible gas source, and its use in foam production has not been shown to cause significant adverse effects. Room air consists mainly of nitrogen (79%) and oxygen (21%).
- Physiological Gas (CO2/O2 Mixture): Some systems, like the commercially available Varithena®, use a mixture of carbon dioxide and oxygen. The advantage of these gases is their higher solubility in blood, which can reduce the risk of temporary side effects like visual disturbances and headache, which are sometimes associated with air-based foams, particularly in patients with a patent foramen ovale. However, the trade-off is often decreased foam stability compared to air foams.
The Method of Preparation: The Tessari Technique
The most widely adopted method for preparing the foam mixture is the Tessari technique, named after Dr. Lorenzo Tessari. This simple, manual method uses a double-syringe system and a three-way stopcock to create a homogenous microfoam.
The standard procedure involves:
- Aspirating a specific volume of the liquid sclerosing agent into one syringe.
- Aspirating a larger volume of gas into a second syringe.
- Connecting the two syringes with a three-way stopcock.
- Rapidly moving the plungers back and forth between the two syringes for 10 to 20 cycles. This turbulent mixing process generates the fine-bubbled, stable foam.
A typical gas-to-liquid ratio for the Tessari method is 1:4 (one part liquid sclerosant to four parts gas) or 1:5, which produces a stable and viscous foam. The foam must be injected shortly after preparation to maintain its stability and effectiveness.
Advantages of Foam Over Liquid Sclerotherapy
The conversion of the sclerosing agent into foam provides several key advantages that increase the efficacy of the procedure, particularly for treating larger veins.
- Blood Displacement: The foam's viscous nature effectively displaces blood from the targeted vessel. This is crucial because it prevents the sclerosant from being immediately diluted by blood, ensuring a higher concentration and longer contact time with the vein wall.
- Extended Contact: A given volume of foam covers a much larger surface area inside the vein than the same volume of liquid. This extended contact and greater coverage amplify the inflammatory reaction needed to close the vein.
- Ultrasound Guidance: The gas bubbles within the foam make it highly visible under ultrasound imaging. This allows the phlebologist to precisely guide the injection and monitor the foam's spread throughout the treatment area, especially for deeper veins.
- Increased Versatility: The improved performance of foam allows for the treatment of a wider range of vein sizes, from small spider veins to larger varicose and truncal veins, often with fewer treatment sessions compared to liquid sclerotherapy.
Comparison of Foam and Liquid Sclerotherapy
| Feature | Foam Sclerotherapy | Liquid Sclerotherapy |
|---|---|---|
| Sclerosing Agent | Detergent (Polidocanol, STS) + Gas | Detergent (Polidocanol, STS), Glycerin |
| Consistency | Viscous, micro-bubble foam | Clear, non-viscous liquid |
| Vein Size | Effective for a wider range, including larger varicose and truncal veins. | Best for smaller veins, such as spider veins and smaller reticular veins. |
| Mechanism of Action | Displaces blood for prolonged contact with vein wall, increasing efficacy. | Mixes with blood, which can dilute the agent and reduce its effectiveness. |
| Ultrasound Visibility | Excellent visibility due to gas content, allowing for guided injections. | Not visible on ultrasound, making guidance for deeper veins difficult. |
| Efficacy | Generally more effective per treatment session, potentially requiring fewer visits. | May require more sessions for optimal results, especially for larger or numerous veins. |
| Minor Side Effects | Higher rates of ecchymosis (bruising) and temporary hyperpigmentation in some studies. | Lower rates of bruising and hyperpigmentation compared to foam. |
Clinical Applications and Safety Considerations
Foam sclerotherapy is a minimally invasive, outpatient procedure performed in a doctor's office. With the aid of ultrasound, a healthcare provider can inject the foam directly into the targeted vein. The foam acts on the vessel, and over the following weeks and months, the treated vein shrinks and is absorbed by the body.
While generally safe and well-tolerated, minor side effects such as bruising, temporary hyperpigmentation, and raised red areas at the injection site can occur. Rare but more serious complications, including deep vein thrombosis, have been reported but occur infrequently. Choosing a board-certified and experienced vein specialist is paramount to ensure the procedure is performed safely and effectively.
It is important for patients to discuss their medical history with their doctor, as certain conditions or medications (e.g., blood thinners) may influence the treatment plan. Following the procedure, patients are often advised to wear compression stockings for a period of time to aid in the healing process and ensure the treated vein remains closed.
Conclusion
The mixture for foam sclerotherapy is a precisely prepared formulation of a detergent sclerosant (like polidocanol or STS) and a gas (usually air). Created using standardized methods such as the Tessari technique, this foam offers significant advantages over traditional liquid sclerotherapy. Its greater viscosity and ability to displace blood lead to more potent and targeted treatment, particularly for larger varicose veins. By understanding the components and preparation, patients can appreciate the pharmacological principles that make foam sclerotherapy a highly effective and versatile option for managing venous disorders. For further information on vascular conditions and treatments, the Journal of Vascular Surgery offers authoritative research.(https://www.jvsvenous.org/article/S2213-333X(21)00200-6/fulltext)
