Fundamentals of laser surgery.

Laser light has unique properties that enable transmission of high amounts of energy to a narrowly defined site. Biological effects may be thermal, chemical, or mechanical. Medical procedures involve mainly thermal tissue destruction by coagulation (> 60 degrees C) or ablation (> 300 degrees C). The effect is governed by tissue optical and thermal properties and laser variables; contact/non-contact, focus, output power (W), and exposure time (s). The laser medium governs the wavelength emitted. The carbon dioxide (CO2) laser light (10600 nm) requires transmission through articulating arms with mirrors, whereas neodymium:yttrium-aluminum-garnet (Nd:YAG) (1064 nm), and argon (488/515 nm) light can be transmitted through flexible quartz fibres. CO2 lasers are used mainly for high precision tissue ablation; Nd:YAG lasers can coagulate or vaporise larger tissue areas and argon laser applications involve vascular destruction, based on selective absorption by haemoglobin. Research has shifted towards a fundamental understanding of the interactions of light with biological tissue to allow treatment planning and to optimise laser procedures. Applications such as interstitial laser coagulation for local destruction of solid tumours deserve further exploration in general surgery.