Foam sclerotherapy is usually given as a secondary treatment for the management of unhealthy or varicose veins. However, several reports have established that most of its principles were developed around fifty years ago. Minor modifications in the creation of foam have been created over the years. The recent utilization of ultrasound to guide the injection of foam to close varicose veins that exhibit reflux, have resulted in an exceedingly revived interest in the technique. Recently, the use of foam sclerotherapy has progressed from experimental studies that established the effectuality and safety of this method to primary randomized controlled trials. We may need long follow-up in properly controlled randomized studies before we are able to claim that ultrasound-guided foam sclerotherapy has reached maturity and may be performed with proper consent of our patients.
In the Nineteen Nineties, there was some refinement of the techniques that created foam and this led to a revived interest in treating unhealthy varicose veins using this form of treatment. Juan Cabrera used a rotating brush to provide micro-foam with C02 as a carrier gas. The advantage of C02 is that the quicker foam degradation is achieved if used rather than air. Juan did not publish the details although the results were good. Alain Monfreux created foam by generating negative pressure. He did this by drawing back the plunger of a glass syringe containing liquid sclerosing resolution whose outlet was tightly closed with a plastic cap. This method produces comparatively larger bubbles (in diameter). Because of this it can’t be standardized. The variance in the mixed foam can cause treatment and outcome variations alike. There needs to be standardization in the creation of the foam that is created consisting of equal proportions of air and liquid to be mixed.
Lorenzo Tessari’s Tourbillon technique is that the most often quoted within literature. In this technique two plastic disposable syringes are connected by a three way stopcock (triangular in shape). The foam is made by intermixture the liquid sclerosant with four or five parts air, through twenty passes between the 2 syringes with the hub at a 30° rotation. This rotation narrows the cock passage generating high turbulence that produces a prime quality micro-foam.
Foam sclerescent is a mixture of gas bubbles in a liquid solution that contains surface-active molecules. At The Vein Center of Arizona we use Asclera or (polidocanol) in .5% or 1% solutions to
create foam. The gas must be tolerated by patients, physiologic, and the bubble size ideally should be under 100 μ. Foam is classified by the bubble diameter and can be classified as foam,
mini-foam,macro-foam and micro-foam.
If the relative volume fraction of liquid is less than 5%, the foam is classified as dry, whereas if it is more than 5%, it is classified as wet. Wet foam is the most stable of the variations. I has the maximum stability. Uniform bubble diameter also provides more stability because smaller bubbles empty into larger bubbles. Laplace's law explains this. It states that the distending pressure in a bubble is inversely proportional to its radius.
Foam holds several advantages over traditional liquid sclerotherapy. Once a liquid is injected, it mixes with blood in the vein and dilutes the concentration of the sclerosant. Foam, on the other hand, displaces the blood allowing direct contact of the sclerosant with the inner layer of the vessel wall or endothelium. As a result, the effectiveness of the sclerosant is increased and a lower concentration can be given to treat varicose veins. Another benefit is that a given volume of liquid can be used to produce up to five times its volume in foam, depending on the method to create the foam. Using a smaller total dose of sclerosant to achieve the desired effect is a monetary and safety benefit. Extravagated foam is much better tolerated than extravagated liquid (sclerescent outside of the vein). Probably the most significant advantage of foam is that it is echogenic (easily seen via ultrasound), which greatly increases the accuracy with which individual varicose veins can be treated.
Most authors cited have injected the foam directly into the great saphenous vein or the small saphenous vein under ultrasound guidance. During this process, the leg is elevated resulting in the reduction of the diameter of the vein. Surveys show that varying amounts are used to treatment saphenous veins, however consensus revealed that a majority of experts inject 2 to 10 mL of foam into the great saphenous vein and 1 to 4 mL into the small saphenous vein. There is no consensus when it comes to tributaries of the saphenous veins, accessory saphenous veins or perforators at this time.