Describe the principles of surgical lasers, their safe use and the potential hazards
A laser is a device for light amplification by stimulated emission of radiation. Laser light is:
All photons move in parallel.
All photons are in phase.
All photons have the same wavelength.
Lasers are used clinically for:
- Precise incisions
Destruction of cells by localised vapourisation of water.
- Destruction of chemicals
Tattoos, oncological drugs.
- Tissue destruction without heating
- An energy source is passed through a lasing medium, housed in a resonator made of mirrors
- As the lasing medium is excited, electons enter a higher energy level
When more than 50% of electrons are at a higher energy level, population inversion has occurred.
- As electrons fall back to their resting state, they release a photon
- A spontaneous emission occurs when an electron enters its resting state spontaneously
- A stimulated emission occurs when an electron enters its resting state after being struck by a photon released from a spontaneous emission
- Stimulated emissions result in amplification of light release
- The mirrors in the resonating chamber enxure most light is reflected back into the chamber, causing more stimulated emissions
- The exit from the chamber can be be adjusted so only certain polarities of light are emitted
- A lens may be used to focus the laser beam
- Lasers may be:
- Pulse wave
Uses short bursts of laser light to minimise collateral damage.
- Continuous wave
May lead to excessive heating.
- Pulse wave
- Precise surgery and haemostasis
- Require multiple safety precautions
- Laser safety officer
- Eye protection
- Warning signs on doors
- Cover theatre windows
- Non-combustible drapes
- Matte finish on equipment to minimise chance of reflection
- Additional risks in airway surgery
- Use lowest FiO2 possible
- Avoid N2O
- Consider use of heliox
- Use specialised laser tubes
Normal PVC ETTs are combustible.
- Aston D, Rivers A, Dharmadasa A. Equipment in Anaesthesia and Intensive Care: A complete guide for the FRCA. Scion Publishing Ltd. 2014.