CO₂ and argon laser vascular welding: Acute histologic and thermodynamic comparison

CO₂ and argon lasers have been used successfully for vascular welding in both experimental and clinical settings. This study compared the thermodynamics during CO₂ and argon laser welding of 1‐cm longitudinal arteriotomies in a canine model. Continuous recordings using an AGA 782 digital thermographic system with spatial and thermal resolution of ±0.2 mm and ±0.2°C, respectively, were analyzed. A HGM argon laser using a 300‐μm optic fiber held at 1 cm from the vessel edges (spot diameter = 2.8 mm) with concomitant room temperature saline irrigation (1 drop/sec) was used for argon welds. Total exposure time was 150 sec/cm. CO₂ welds were performed with a Sharplan CO₂ laser (spot diameter = 0.22 mm) with no irrigation for total exposure time of 10 sec/cm. Thermodynamic results and laser parameters are summarized as follows: Argon–n = 20; power = 500 mW; energy fluence = 1,400 J/cm²; Tmax = 48.8°C; T mean ± S.D. = 45.1 ± 2.7°C; CO₂–n = 20; power = 150 mW; energy fluence = 3,000 J/cm²; Tmax 84.0°C; T mean ± S.D. = 60.7 ± 9.8°C. There was a significant difference (P < .05) in thermal measurements between successful CO₂ and argon vascular welds. Temperature rise during the argon welds was limited by saline irrigation. In contrast, during CO₂ laser welding, the temperature rose quickly to its maximum and was maintained at a relatively high level as the laser progressed (0.1 cm/sec) along the anastomosis. Histologic examination revealed charring at the CO₂ weld site but absence of thermal damage at the argon laser weld. These thermodynamic differences may account for the different welding mechanisms currently described.