Stefano Ricci
AbstractIn a recent article, Cavezzi and Tessari speculated that the addition of glycerin may prolong half liquid time. The Authors studied the stability of sodiumtetradecyl sulphate (STS) after addition to glycerin 72%. The sclerosant combinations investigated were: 1.0 mL 0.5% STS to 0 mL 72% glycerin; 0.9 mL 0.5% STS to 0.1 mL 72% glycerin; and 0.8 mL 0.5% STS to 0.2 mL 72% glycerin.
For each trial, 1.0 mL of 0.50% STS sclerosant was charged using new sterile syringes and connectors attached to a W/W adaptor and to a 5 mL syringe with 4 mL of pre-drawn air. Using the double-syringe system technique, air is pushed to fill the syringe with the sclerosing agent. This method usually requires ten passages from one syringe to the other. Finally, the 5 mL syringe filled with the foam iss placed exactly vertically with the rubber stopcock on the bottom and the timer is started. As the foam degenerates back into its constituents, the sclerosing solution gradually re-forms at the bottom of the syringe. When the solution’s meniscus reaches a volume of 0.5 mL (half of the original sclerosing volume of 1.0 mL), the timer is stopped and data are recorded. Table 1 clearly shows that the addition of glycerin to foam prolongs foam stability due to the increased viscosity of glycerin, increasing the STS foam half-life by 35.29%.
Possibly more efficacious sclerotherapy could be achieved from a prolonged contact time of the foam bubbles with the endothelial cells. However, this same prolonged stability could cause an increase in the incidence of distant side effects. The most effective amount of glycerin into the solution still needs to be studied.
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Table 1. Foam half-life stability. |
Foam never ceases to surprise us! The most interesting aspect of this method is its simplicity, with consequent low costs and easy availability for use in research and development. This is in spite of all attempts to change the foam sclerotherapy into a commercial business. Tessari’s inventiveness must again be recognized. In the paper in question, as the CO2 foam is less stable, although more harmless, adding a stabilizer to this gas-based foam could be of particular interest. Much research is still needed into the association of tensioactive (foaming) agents with other traditional sclerosing non-foaming agents, such as glycerin and also iodine. We must not forget also the possible association with other surgical or endovascular treatment methods, an aspect which up till now has been completely neglected. Those interested in the subject may read Cavezzi and Tessari’s paper for themselves: Foam sclerotherapy techniques: different gases and methods of preparation, catheter versus direct injection. Phlebology 2009;24:247-51.
The story of foam is even more interesting when we consider that the duration and quality of foam is also influenced by the type of syringe used to make it. Each syringe manufacturer uses a different type of plastic and silicon to coat the inside barrel of the syringe. This has been studied in Lai and Goldman’s paper: Does the relative silicone content of different syringes affect the stability of foam in sclerotherapy? J Drugs Dermatol 2008;7:399-400.
This study examined the possibility that relative silicone content of different syringes may affect the overall foam stability. A double-syringe system (DSS) technique to make sclerosing foam (STS 0.5% and air) was applied. Four different brands of syringes were tested. The time required for half of the original volume of sclerosing solution to settle was recorded. The time for the sclerosing solution to settle to half of its initial volume varied with each brand of syringes. The type of syringe used in the DSS technique to produce foam for sclerotherapy is a determinant of foam stability. Whether this will affect the result of sclerotherapy requires further investigation.
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