Physical Vein Models to Quantify the Flow Performance of Sclerosing Foams

The Stability of Physician-Compounded Foam is Influenced by the Angle of Connector

BACKGROUND

Foam sclerotherapy is an effective treatment for varicose veins and venous malformations, with its efficacy influenced by foam stability. The methods for preparing physician-compounded foam (PCF) are the double syringe system (DSS) and Tessari method. Few studies have been performed to compare the PCF stability produced by the 2 methods and their mechanisms. We aim to compare the stability of PCF produced by 2 two methods in the same connector and explore the reasons for the difference.

METHODS

Foam was generated by the 2 methods under different circumstances. In the Tessari method, 2 syringes were connected at right angles (90°) by a 3-way tap. In the DSS method, 2 syringes were connected by the same 3-way tap in a straight line (180°). The stability and uniformity of foam produced by the 2 methods were compared using foam half-time and optical microscopy, respectively. Assuming that the difference in foam stability between the 2 methods was related to the angles of a connector, we compared the foam stability when 2 syringes were connected with a plastic connector bent to different angles.

RESULTS

The DSS method could produce more uniform foam with longer foam half-time than the Tessari method, which was related to the angle of the connector.

CONCLUSIONS

The stability of PCF is influenced by the angle of the connector.

Anti-Inflammatory and Antioxidant Effects of Diosmetin-3-O-β-d-Glucuronide, the Main Metabolite of Diosmin: Evidence from Ex Vivo Human Skin Models

Diosmin is used to relieve chronic venous disease (CVD) symptoms. This study aimed to investigate the anti-inflammatory and antioxidant effects of diosmetin-3-O-β-d-glucuronide, the major metabolite of diosmin, using human skin explants. The explants were exposed to substance P (inflammation model) or UVB irradiation (oxidative model) and to five diosmetin-3-O-β-d-glucuronide concentrations. Inflammation was evaluated through interleukin-8 (IL-8) secretion measurements and capillary dilation observation, and oxidation was evaluated by measuring the hydrogen peroxide levels and observing cyclobutane pyrimidine dimers (CPDs). In substance-P-exposed explants, diosmetin-3-O-β-d-glucuronide induced a significant decrease in IL-8 secretions, with a maximal effect at 2700 pg/mL (-49.6%), and it reduced the proportion of dilated capillaries and the mean luminal cross-sectional area (p < 0.0001 at all tested concentrations), indicating a vasoconstrictive effect. In UVB-irradiated fragments, diosmetin-3-O-β-d-glucuronide induced a significant decrease in hydrogen peroxide production and in the number of CPD-positive cells, reaching a maximal effect at the concentration of 2700 pg/mL (-48.6% and -52.0%, respectively). Diosmetin-3-O-β-d-glucuronide induced anti-inflammatory and antioxidant responses, with the maximal effect being reached at 2700 pg/mL and corresponding to the peak plasma concentration estimated after the oral intake of 600 mg of diosmin, the daily dose usually recommended for the treatment of CVD. These ex vivo findings suggest a protective role of diosmetin-3-O-β-d-glucuronide against inflammatory and oxidative stress affecting the vascular system in CVD pathophysiology.

Foam-in-Vein: Characterisation of Blood Displacement Efficacy of Liquid Sclerosing Foams

Sclerotherapy is among the least invasive and most commonly utilised treatment options for varicose veins. Nonetheless, it does not cure varicosities permanently and recurrence rates are of up to 64%. Although sclerosing foams have been extensively characterised with respect to their bench-top properties, such as bubble size distribution and half-life, little is known about their flow behaviour within the venous environment during treatment. Additionally, current methods of foam characterisation do not recapitulate the end-point administration conditions, hindering optimisation of therapeutic efficacy. Here, a therapeutically relevant apparatus has been used to obtain a clinically relevant rheological model of sclerosing foams. This model was then correlated with a therapeutically applicable parameter-i.e., the capability of foams to displace blood within a vein. A pipe viscometry apparatus was employed to obtain a rheological model of 1% polidocanol foams across shear rates of 6 s^-1 to 400 s^-1. Two different foam formulation techniques (double syringe system and Tessari) and three liquid-to-gas ratios (1:3, 1:4 and 1:5) were investigated. A power-law model was employed on the rheological data to obtain the apparent viscosity of foams. In a separate experiment, a finite volume of foam was injected into a PTFE tube to displace a blood surrogate solution (0.2% w/v carboxymethyl cellulose). The displaced blood surrogate was collected, weighed, and correlated with foam's apparent viscosity. Results showed a decreasing displacement efficacy with foam dryness and injection flowrate. Furthermore, an asymptotic model was formulated that may be used to predict the extent of blood displacement for a given foam formulation and volume. The developed model could guide clinicians in their selection of a foam formulation that exhibits the greatest blood displacement efficacy.

Foam-in-vein: A review of rheological properties and characterization methods for optimization of sclerosing foams

Varicose veins are chronic venous defects that affect >20% of the population in developed countries. Among potential treatments, sclerotherapy is one of the most commonly used. It involves endovenous injection of a surfactant solution (or foam) in varicose veins, inducing damage to the endothelial layer and subsequent vessel sclerosis. Treatments have proven to be effective in the short-term, however recurrence is reported at rates of up to 64% 5-year post-treatment. Thus, once diagnosed with varicosities there is a high probability of a permanently reduced quality of life. Recently, foam sclerotherapy has become increasingly popular over its liquid counterpart, since foams can treat larger and longer varicosities more effectively, they can be imaged using ultrasound, and require lower amounts of sclerosing agent. In order to minimize recurrence rates however, an investigation of current treatment methods should lead to more effective and long-lasting effects. The literature is populated with studies aimed at characterizing the fundamental physics of aqueous foams; nevertheless, there is a significant need for appropriate product development platforms. Despite successfully capturing the microstructural evolution of aqueous foams, the complexity of current models renders them inadequate for pharmaceutical development. This review article will focus on the physics of foams and the attempts at optimizing them for sclerotherapy. This takes the form of a discussion of the most recent numerical and experimental models, as well as an overview of clinically relevant parameters. This holistic approach could contribute to better foam characterization methods that patients may eventually derive long term benefit from.