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:

  • Non-divegent
    All photons move in parallel.
  • Coherent
    All photons are in phase.
  • Monochromatic
    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, electrons 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 ensure 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.


  • 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.


  1. Aston D, Rivers A, Dharmadasa A. Equipment in Anaesthesia and Intensive Care: A complete guide for the FRCA. Scion Publishing Ltd. 2014.
Last updated 2019-07-18

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