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Sodium tetradecyl sulphate foam stability prior to injection: factors affecting liquid reformation

Objective To study the effect of sclerosant concentration, use of 5-µm filter, use of CO2 versus air and needle size on the stability of sodium tetradecyl sulphate (STS) foam and observe the dynamics of liquid reformation from foam within the syringe prior to injection. Method Observations of liquid reformation within the syringe following foam preparation using the Tessari method. Result Foam stability varies little with STS concentration between 0.5% and 3%. Needle size has little effect in this study. An in-line filter produces significantly more stable foam, and CO2 foam is significantly less stable than air foam. Liquid reformation is predictable and does not progress at a constant rate. Conclusion Regardless of the method and details of the foam produced, sclerotherapists should be aware of the dynamics and speed of foam degradation, and reconstitute foam at the first sign of liquid reformation, as this heralds the onset of rapid degradation of the foam. This is particularly relevant for rapidly deteriorating foam produced from CO2, or without the use of a filter.