Numerical simulation of endovenous laser treatment of the incompetent great saphenous vein with external air cooling

Abstract

Endovenous laser treatment (ELT) has been proposed as an alternative in the treatment of reflux of the great saphenous vein. Before the procedure, peri-saphenous subcutaneous tumescent saline solution infiltration is usually performed. However, diffusion of this tumescent fluid is rapidly observed and can potentially reduce the efficacy as a heat sink. External skin cooling with cold air was proposed as an alternative solution. The objective of this study is to compare endovenous laser treatment without and with air cooling by realistic numerical simulations. An optical-thermal damage model was formulated and implemented using finite element modeling. The general model simulated light distribution using the diffusion approximation of the transport theory, temperature rise using the bioheat equation, and laser-induced injury using the Arrhenius damage model. Parameters, used in clinical procedures, were considered: power, 15 W; pulse duration, 1 s; fiber pull back, 3-mm increments every second; cold air applied in continuous mode during ELT; and no tumescent anesthesia. Simulations were performed for vein locations at 5, 10, and 15 mm in depth, with and without air cooling. For a vein located at 15 mm in depth, no significant difference was observed with and without cooling. For a vein located at 10 mm in depth, surface temperature increase up to 45 °C is observed without cooling. For a vein located at 5 mm, without cooling, temperature increase leads to irreversible damage of dermis and epidermis. Conversely, with air cooling, surface temperature reaches a maximum of 38 °C in accordance with recordings performed on patients. ELT of the incompetent great saphenous vein with external air cooling system is a promising therapy technique. Use of cold air on the skin continuously flowing in the area of laser shot decreased significantly the heat extent and the thermal damage in the perivenous tissues and the skin.

A Comparative Study of the Efficacy of Endovenous Laser Treatment of the Incompetent Great Saphenous Under General Anesthesia with External Air Cooling with and Without Tumescent Anesthesia

“…Even if the vein was located 5 mm below the skin, the surface temperature remained below 40°C. 12 This value is similar to the temperature measured at the surface of the skin with the infrared thermometer: 40.3 AE 1.8°C.…”

“…These results confirmed the numerical simulations that our group performed. 12 No skin burns were reported, and surgical time was significantly shorter than for ELT with tumescent anesthesia. Safety standards were upheld, and surgical and recovery times were drastically reduced.…”

“…We have recently performed numerical simulation of ELT of the incompetent great saphenous vein with external air cooling. This simulation has showed that cold air on the skin continuously flowing in the area of laser application significantly decreased heat and thermal damage in the perivenous tissues and skin (Figures and ) …”

“…This simulation has showed that cold air on the skin continuously flowing in the area of laser application significantly decreased heat and thermal damage in the perivenous tissues and skin (Figures 1 and 2). 12 To determine the benefits and drawbacks of the method, such as avoidance of complications and reduction in overall operating time while maintaining efficacy and safety, two groups of patients were treated. One group was treated using the classical tumescent anesthesia method and served as a reference; the other group was treated with air cooling.…”

Side effects and occlusion rate after tumescentless treatment of the great saphenous vein with EVLA

“…so called "hemoglobin-absorbing" and "water-absorbing" lasers) is generally unimportant for final thermal and consequently clinical effect. Numerical simulation of EVLA treatment of great saphenous vein (GSV) suggested that as long as the vein is located more than 10 mm below the skin surface the temperature of the skin does not exceed 45°C (6). Back in 2002 we noted that our patients who had undergone EVLA in intravenous sedation or regional anaesthesia due to either personal preferences or insurance requirements and treated without tumes-cent solution experienced actually less pain and bruising than those injected with the solution.…”