The History of Sclerosing Foams

More documents

Recommendations

Info

Dermatol Surg 30:5:May 2004 WOLLMANN: THE HISTORY OF SCLEROSING FOAMS 695 Figure 1. Overview about the contributions to foam sclerotherapy. proximal tourniquet, blood could flow into the central or more proximal direction, while the distal tourniquet reduced or eliminated the supply of new blood from distally. This technique caused less dilution of the liquid sclerosing agent. Nevertheless, he sometimes noticed therapeutic failures, so he had the ‘‘famous idea’’: to intensify the contact between the sclerosant and the endothelium, the diameter of the vein should not only be reduced as far as possible prior to injection, but the vein should be rather free from any blood. Therefore, he injected a small amount of air into the venous segment to be treated to completely displace the remaining blood (see Figure 2). Experimentally, he had shown that 1 cm 2 of air injected into a 6-mm infusion tube pending vertically and filled with water did not separate into several ascending bubbles but remained in the area of injection as one large bubble, if the injection was not given too slowly. He then injected a colored solution into this air bubble, which, over a period of 3 to 5 s, did not get mixed with water but remained undiluted in the ‘‘air pocket.’’ Clinically, he used the ‘‘air-block technique’’ only for smaller and medium-sized varicose veins; He recommended the conventional technique, without air injection, for larger veins. Unfortunately, Orbach’s article does not reveal the reasons for this recommendation. It remains unclear why the method that he considered to be more effective should not be suited for large varicose veins which usually were more difficult to treat. In 1970, Stemmer 4 et al. showed in an experiment that the air-block technique was only reliable with vessel diameters of up to 4 mm and was never successful with diameters of more than 8 mm. Sclerosis was rather impeded with such diameters: The air bubble floating on the blood column protected the vessel from contact with the sclerosant at the upper Figure 2. The air-block technique: a small amount of air was injected before (top) the injection of sclerosant (bottom) to avoid dilution of the liquid. Figure 3. The air-block technique in large vessels: A floating air bubble (top) was able to prevent contact between the endothelium on the upper vessel wall and the sclerosant. circumference (see Figure 3), thus being effective only partially. The original air-block technique is basically no longer used today, but its development to a ‘‘foam block’’ (air block with large-bubbled foams) is still used today by some phlebologists under various names for smaller vessels. Small advantages in efficacy (increase by 20%) are believed to be outweighed by the disadvantages (plus 100% side effects). 5 The maximum amount of air injected was 3 mL, a limit that became an orientation for most physicians using the air-block technique. 1944—Robert Rowden Foote: 6 Foam in Feeder Veins with Shaking-the-Syringe Technique In the same year as Orbach’s publication, a book by Robert Rowden Foote was published in London. In addition to an overview of his ‘‘empty-vein technique,’’ he wrote about the treatment of spider veins: ‘‘The feeder vein should be dealt with first, whenever possible. The best injection fluid is the soapy froth obtained by shaking up 1 cc of ethamoline (ethanolamine oleate) in a 2-cc syringe. [It should be mentioned that the ratio of 1 plus 1 is, strictly speaking, not foam but an air/liquid dispersion. Usually a mixture is defined as foam if the gas portion is higher than 0.52. 7 A characteristic order of magnitude of gas/fluid systems is the gas proportion j. Depending on the gas proportion, distinction is made between gas dispersion, spherical foam (wet foam), and polyhedral foam (dry foam). In gas dispersions, there are individual air bubbles in liquid; the gas proportion j is less than 0.52. In the spherical foam, the number of individual bubbles is higher— there is still a rather high amount of liquid; the gas
696 WOLLMANN: THE HISTORY OF SCLEROSING FOAMS Dermatol Surg 30:5:May 2004 proportion is 0.524j40.74. In the polyhedral foam, in contrast, the amount of liquid between the bubbles is so small that the individual bubbles get closer and closer to each other, thus forming polyhedrons. The gas proportion j is greater than 0.74. In a foaming fluid (e.g., beer), all types generally occur, the polyhedral foam being above the spherical foam and the gas dispersion and liquid below.] Once the needle is in the vein, the bubbles can be made to course along the minute veins and can be followed visually in their transit.’’ Nowadays, ethanolamine oleate is no longer available in most countries. The ‘‘agitation technique’’ was refined in the following years and is no longer in use. The air:sclerosant ratio of 1 plus 1 described by Foote suggests that the dispersion was very fluid so that it could not be used for displacing the blood in larger diameter veins. 1949—Karl Sigg: 8 Foam-Block Technique and Viscosity of Foam In 1949, Karl Sigg picked up the air-block technique described 5 years before: Also for other varices than spider veins, i.e., larger veins, he used the new technique and reported more than 4000 treatments performed ‘‘without problems.’’ Sigg describes the rationale for the use of the air-block technique in a similar manner as Orbach and Foote: ‘‘The purpose is to prevent the dilution of the solutions for injection in the vein by the blood and to ensure that the sclerosant gets in contact with the intima of the vein in a rather concentrated formy. Even with this small-scale use, the air bubble chased the blood before the injection fluid arrived and thus cleared the way for a closer contact of the sclerosant with the venous intima.’’ Later, Sigg combined Orbach’s air-block technique and Foote’s foam application and thus introduced a new aspect into the therapeutic options known to that date: ‘‘Orbach’s method becomes even more beneficial if foam is injected instead of airy. This foam is less rapidly washed away in the varicose vein than it happens with the pure injection of air.’’ Thus Sigg introduced for the first time the idea (even if not pronounced) of increased viscosity of foam. With the use of foam, he improved the air-block technique (introducing a foam block), but without omitting the fluid sclerosant (see Figure 4). Sigg described his own procedure for the manufacture of foam; the glass syringe filled with fluid sclerosant was held with the opening pointing downward. Approximately 1 mL of air was aspirated through it, pearls developed in the solution, and thus more or less large bubbles were generated in the syringe. Figure 4. The foam-block technique: First, foam was injected to maintain the displacing effect of the air block for a longer time (top), and then normal liquid sclerosant was injected (bottom). 1950—Egmont James Orbach: 9,10 Vasospasm after Foam Sclerotherapy A later publication by Orbach reveals the first attempt to compare the efficacy of foam (administered as air block and foam) with the efficacy of fluid sclerosants. The end point was the length of the sclerothrombus generated by the injection of the respective substance. The efficacy of the foam generated by agitation of the syringe or drug vial was increased approximately 3.5to 4-fold compared with the same amount of ‘‘conventional’’ fluid. The observation of a ‘‘marked vasospasm’’ after injection of foam is nowadays considered to be an important immediate end point for the assessment of the efficacy of modern sclerotherapy. 11–13 This (reversible) vasospasm, which is often clearly detectable in duplex-guided sclerotherapy, can be considered to be a sign of initial vascular damage after sclerotherapy. After administration of a viscous foam, vasospasm is more common and more pronounced than after sclerotherapy with conventional fluid. 42 An important factor in this respect is that a given volume of a blood-displacing foam can spread over a much longer venous segment after a vasospasm occurs and can even act at a certain distance from the site of administration. (For example, 1 mL of a viscous foam completely fills a vein of 8 mm in diameter over a length of approximately 20 mm. A reduction of the vessel diameter owing to spasm to 2 mm distributes the same foam volume to a length of almost 32 cm. In vivo, a spasm of a mean length of 28 cm could be provoked with vessels of 4 to 8 mm in diameter and a foam application of 2 to 2.5 mL of double-syringe-system foam.) As long as vasospasm exists, venipuncture at the same site is aggravated. The use of small venous cannulae or catheters may help dealing with this. Because foams in current use are very different from those used by Orbach, it is impossible to draw conclusions about the general efficacy of foam from this experiment. Nevertheless, according to all findings and based on theoretical considerations, the efficacy of foam is always higher than that of the same amount and concentration of fluid. The level of increased efficacy cannot be predicted in the individual case without sufficient standardization. The increased
Page 1: The History of Sclerosing Foams JAN
Page 5 and 6: 698 WOLLMANN: THE HISTORY OF SCLERO

The History of Sclerosing Foams

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?