Laser tissue welding in minimally invasive surgery and microsurgery

Lasers have become already a widespread tool in many operative and therapeutic applications in the surgical field. The so-called "minimally invasive" laser techniques provide remarkable improvements: in these, laser surgery is performed inside the human body through small incisions by means of optical fibre probes and endoscopes, or laser tools are proposed as a replacement for conventional tools to minimize the surgical trauma, such as in the case of laser-induced suturing of biological tissues. The aim of these procedures is to improve the quality of life of patients, by decreasing healing times and the risk of postoperative complications. Many types of lasers have been proposed for laser tissue welding. Infrared and near-infrared sources include carbon dioxide (CO2), thulium-holmium- chromium, holmium, thulium, and neodymium rare-earth-doped-garnets (THC:YAG, Ho:YAG, Tm:YAG, and Nd:YAG, respectively), and gallium aluminium arsenide diode (GaAlAs) lasers. Visible sources include potassiumtitanyl phosphate (KTP) frequency-doubled Nd:YAG, and argon lasers. The laser energy is absorbed by water at the infrared wavelengths and by haemoglobin and melanin at the visible wavelengths, thereby producing heat within the target tissue. As the temperature rises, the extracellular matrix of the connective tissue undergoes thermal changes that lead to the welding of the wound (Fig. 15.1).