May-June 2013 Issue - American College of Phlebology

COMMENTARY
The clinical phlebologist is well aware that
sclerosants act at limited areas of clinical activity
from the point where they are injected. In the past,
it was felt that this clinical observation was related
to the dilution of the sclerosant and its subsequent
decreased potency in this regard, based solely upon
concentration/sclerosant endothelial interaction
kinetically.
in practical use, it
would take less than
0.5% ml of whole
blood to deactivate
1 ml of 3% STS
In addition, a commonly known observation is that foam sclerosants manifest greater potency and also have more significant
distal watershed-type effect. With these tenets in mind, the article entitled “Deactivation of sodium tetradecyl sulphate
injection by blood protein” brings new insight and rationale into the actual pathophysiologic mechanisms of this clinical
observation.
The present study looked at the volume of blood required to inactivate 1ml of 3% sodium tetradecyl sulphate. This was
accomplished by measuring the concentration of sodium tetradecyl sulphate (STS) remaining in the active state in an in-vitro
stock solution after adding increasing volumes of solution containing either bovine serum albumin or red blood cells or a
mixture of both components. The two methodologies utilized to assess the results included autotritation and colorimetry.
Results of the aforementioned study showed that STS is deactivated by blood proteins in a linear fashion. The protein
solution utilized seemed to make little difference, with approximately 2 ml of 4% protein solution deactivating 1 ml of a 3%
STS solution.
The authors hypothesized that titration measured the free STS remaining in solution after the addition of blood proteins
which would bind and deactivate the STS and this correlates with clinical activity. These results suggest that in practical
use, it would take less than 0.5% ml of whole blood to deactivate 1 ml of 3% STS which would explain why an empty vein
technique is important when injecting liquid sclerosant in the varicose veins, a concept that is well-documented in clinical
practice since its description by Orbach. 1
This would explain the noted limited distance of clinical efficacy of injected liquid sclerosants.
Limitation of this study would include its in-vitro design and qualitative visual assessment as related to the colorimetric
assay employed in the study design. The authors also confirm that it was difficult to visually determine the end point of
titration with increasing volumes of blood proteins, which is why the average of up to four individual readings was utilized.
1 Orbach EJ. Sclerotherapy of varicose veins—utilization of an intravenous air block. Am J Surg 1944;LXVI(3):362–6.
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