Foam Sclerotherapy: Management of Varicose Veins
Principles and Technique of Foam Sclerotherapy.
Foam sclerotherapy is a minimally invasive technique to eliminate unsightly varicose veins and spider veins. The procedure involves injecting a foam sclerosant into a blood vessel to close it. The blood reroutes itself through healthy veins, restoring more normal blood flow.
Foam sclerotherapy was first described in 1939. Several reports in the 40s and early 50s established most of the principles of this technique. More recently, well-documented observational studies have demonstrated a good safety profile and satisfactory short and intermediate results with foam sclerotherapy.
Definitions and Properties of the Foam Sclerotherapy
Foam Sclerotherapy used a mixture of gas bubbles in a liquid solution that contains surface-active molecules. The gas must be well tolerated by patients, physiologic, and the bubble size should be, preferably, under 100 μ. According to the bubble diameter, foams can be classified as froth, macrofoam, minifoam, and microfoam.
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 (eg, Tessari’s foam) has the maximum stability.
Uniform bubble diameter also provides more stability because smaller bubbles empty into larger bubbles. This can be explained by Laplace law, which states that the distending pressure in a bubble is inversely proportional to its radius.
Frullini was likely the first to emphasize that silicon, which is present in catheters and syringes, interferes with the structure of the sclerosing foam by breaking the links of polar macromolecules thus reducing the half-life of the foam.
He concluded that the shorter the contact of such molecules with silicon the better the quality and duration of the foam.
The 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 endothelium.
As a result, the efficacy of the sclerosant is increased hence a lower concentration can be given to treat varicose veins. In addition, a given volume of liquid can be used to produce four or five times its volume in foam, depending on the foaming method.
This allows the use of a smaller total dose of sclerosant to achieve the desired effect. Moreover, extravasated foam is much better tolerated than extravasated liquid.
Probably the most significant advantage of foam is that it is echogenic, which dramatically 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 control.
During this process, the leg is elevated resulting in the reduction of the diameter of the vein. A survey has 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.
How Does Foam Sclerotherapy Work?
When a solution is injected into a vein it is immediately diluted by the blood, reducing its efficacy. Foam pushes the blood out of the way and completely fills the vein: the foam is not diluted by the blood. In fact, far less solution has to be injected to obtain the same effect.
Contact with blood strongly inhibits liquid or foam sclerosants so that they are only effective in the vein into which they have been injected. Once the foam reaches large veins and mixes with blood it is inactivated.
The gas is breathed out and the sclerosant solution is metabolized by the liver within a few hours. Blood now returns to treated vein which has been left without its non-stick lining.
Blood now sticks to the wall of the vein and blocks it off, which is usually a permanent cure for a varicose vein.
Foam Sclerotherapy Procedure
Treatment is usually performed in a treatment room or ultrasound examination room, and not an operating theatre. The patient rests comfortably on a bed. Very little discomfort results from the injections so no sedation or anesthetic is required.
In order to treat large varicose veins, it is necessary to block the main vein feeding the varices. This could be done surgically, but with foam treatment, all that is necessary is to put a needle into the main affected surface vein.
This is the only part of the procedure which might cause discomfort and is usually performed with a small amount of local anesthetic. The position of the needle is carefully monitored using ultrasound imaging so that it is in exactly the right place.
Next, the foam is injected whilst watching its progress using the ultrasound machine. Surprisingly, injecting the foam causes no discomfort, although the leg may ache slightly afterward.
The varicose veins in the leg are checked to see if foam has entered these from the main surface vein where the injection was given.
A few further injections are usually given through a tiny needle in order to make sure that all the varicose veins have been completely injected. The whole treatment usually takes no more than 20 – 30 minutes.
Finally, a firm bandage is applied to the leg. The aim of this is to keep the veins compressed so that they do no fill with blood when the patient stands up.
The bandage is usually worn for a week or two followed by an elastic compression stocking for a further week.
When the bandages are removed at the follow-up appointment it is usual to find that all the varicose veins have gone. Sometimes small lumps can be felt beneath the skin. The leg may be a little bruised, although this is usually fairly minor.
Lumps present at this stage slowly resolve over several weeks. If any varicose veins have not been completely treated in the first session they are injected and the leg bandaged to complete removal of all veins.
If varicose veins are present in both legs it is standard practice to treat them on separate occasions about two weeks apart. This avoids having both legs bandaged at once.
Who is Suitable for Foam Sclerotherapy?
Most patients with small or moderate size varicose veins can be treated in this way. Those patients with very extensive large varicose veins are usually best treated surgically to obtain a more rapid result.
Some patients with large veins lying close to the skin are better treated surgically since brown discoloration of the skin over the treated vein may occur.
If there has been previous surgery to the veins of the leg this does not cause any difficulty in using foam sclerotherapy. In fact, it is often far easier to treat recurrent varicose veins by foam injections than by more surgery.
Careful studies have shown that foam sclerotherapy is the most effective way of treating varicose veins which have recurred after previous surgery.
If varicose veins recur some years after initial treatment then it is straightforward to use the same method foam sclerotherapy again.