# Overview on the Evolution of Laser Welding of Vascular and Nervous Tissues
## 2 Laser Welding of Vascular and Nervous Tissues
### Laser Technology  
According to literature, the most commonly used medical lasers are CO\({}_{2}\), argon, and Nd:YAG. The CO\({}_{2}\) and argon lasers are those with the most suitable application in medical surgeries due to their laser properties and their biological compatibility [40; 41; 46; 73]. The application of these lasers is characterized by their coagulation, vaporization, and disruption capabilities [44]. Considering the published research on laser welding of vascular and nervous tissues, it is possible to define the most reported surgical application for each type of laser. The main applications, advantages, and drawbacks of CO\({}_{2}\), argon, and Nd:YAG lasers are displayed in Table 3.  
An overview of the histological results of CO\({}_{2}\) and argon repairs over conventional suturing is summarized in Table 4. Regarding the vascular argon laser-welding repairs, the results are superior when compared to conventional suture application. [PERSON] et al. [44] reported that the biological effects  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Laser** & **Suitable Surgeries** & **Advantages** & **Drawbacks** \\ \hline \multirow{3}{*}{Argon} & \multirow{3}{*}{Vascular repairs} & Deep vessel wall penetration with lower energy output [41] & Nerve absorption of laser light is minimum due to the lack of presence of significant chromophores [73] \\ \hline \multirow{3}{*}{CO\({}_{2}\)} & Nerve repairs & High energy output [41] & Used primarily to cut and vaporize tissue [44] \\ \cline{2-3}  & & Low penetration depth [45] & Low strength in arterial repairs, cannot sustain systemic pressures [57] \\ \hline \multirow{3}{*}{Nd:YAG} & \multirow{3}{*}{Vascular repairs} & \multirow{3}{*}{Easy penetration of the tissue [44]} & Limited to microvascular anastomoses surgeries [41] \\ \cline{1-1} \cline{4-4}  & & & Produces deep uncontrolled thermal injury due to excessive energy density [44] \\ \cline{1-1} \cline{4-4}  & & Low strength in arterial repairs, cannot sustain systemic pressures [57] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Argon, CO\({}_{2}\), and Nd:YAG characteristics in vascular and nerve laser-welding repairs.  
Figure 3: Visual identification scores and adequate laser-welding end point [45; 56].  
of argon laser welding in vascular healing presented a minimal inflammatory response, near normal collagen content, and no aneurysm formation. The optimal vascular results of argon laser welding have been corroborated by other authors along the years [41; 42; 57; 71]. Nervous CO\({}_{2}\) laser-welding repairs also presented evolutionary results. Specifically, [PERSON] et al. [50] concluded that CO\({}_{2}\) laser-welded nerve coaptations can be performed with higher functional recovery rates than those achieved by nerve sutures. Additionally, [PERSON] et al. [75] and [PERSON] et al. [48] showed that the use of infrared (IR) diode lasers can be excellent alternatives. At wavelengths of 1450, 1940 and 1950 nm, water presents high absorption coefficients, which enables laser-welding repairs to be performed without additional materials, while still obtaining good surgical results, such as minimal aneurysm formation. Another alternative to CO\({}_{2}\) and argon laser welding can be the potassium titanyl phosphate (KTP) laser-welding technique. According to [PERSON] et al. [50], it has a better functional recovery than CO\({}_{2}\) laser welding, i.e., 92.4% against 86.8%.