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Effects of laser on subdermal fat tissue

Dr Serge Mordon, INSERM, Lille University Hospital, Lille, France et al. Histological Evaluation of Laser Lipolysis: Pulsed 1064 nm Nd:YAG Laser Versus CW 980 nm Diode Laser

After adequate anaesthetic infiltration, through the insertion of a 1 mm calibre flexible cannula in the fat tissue, the laser power is transmitted to the adipocytes so that they absorb the power, expand in volume and then break. The histological analyses made after the laser delivery effect on human tissue display areas of reversible cell damage (tumefaction), areas of irreversible damage (lysis) and a reduction in bleeding intensity.

The mechanisms that cause these effects are thermo-dependent, they are reliant on the amount of power accumulated in the area. For low power emissions, only adipocyte tumefaction is observed while for total higher power emissions, destruction of the fat cells and coagulation of the vessels takes place. Due to the heat confined in the adipocytes, the membranes are broken down, but the effect is not only thermal, it is also photomechanical.

Trials by Badin and Geronemus certify that the irreversible cell damage is dependent on power, it is necessary to emit 3 kJ concentrated in a specific area to destroy 5 cm3 of fat tissue.

Two devices are used; one is a Neodymium Yag laser with short pulse delivery of 100 microseconds and 150 milli joules per pulse and a frequency of 40 Hz. That is to say, power at 6 W (6 J/sec). The other device is a laser diode at 980 nm with the option of working at power of 6-10 and 15 watts.

It is transmitted in the fat tissue with both devices, with exposure time of 1-3 seconds in all.It is transmitted in the fat tissue with both devices, with exposure time of 1-3 seconds in all.

The histological changes are as follows:

• In non-irradiated lipoaspirated tissue tunnels created by the fibre are observed although the adipocytes are round and are not deformed or swollen.

• Tunnels are also observed in the irradiated tissues produced by the optical fibre at 300 microns.

• After 1 second of Nd:YAG emission, adipocyte tumescence is observed with an alteration in its rounded shape and an increase in total size. So that in comparison with a normal average adipocyte with a diameter of 75 microns, these adipocytes reach 110 microns.

• After the 2 second Nd:YAG emission, disrupted adipocyte membranes are observed.

• After the 3 second Nd:YAG emission, heat-coagulated collagen fibres appear together with a significant appearance of irreversible adipocyte damage with cytoplasmic retraction and membrane disruption. Coagulated blood cells were also present.

• After 980 nm diode at 6 W, the changes observed were the same.

• With 980 nm diode laser at 10 and 15 W, more adipocyte disruption, destruction of collagen fibres and coagulation of small vessels are observed. For power settings at 45 J, carbonisation of fat tissue involving fibres and membranes was clearly seen with immuno-reactivity for PS 100.

With 980 nm diode laser at 10 and 15 W, more adipocyte disruption, destruction of collagen fibres and coagulation of small vessels are observed. For power settings at 45 J, carbonisation of fat tissue involving fibres and membranes was clearly seen with immuno-reactivity for PS 100.

The heat acts on the fat cells and the extracellular matrix to produce both reversible and irreversible effects. The low power parameters produce reversible damage making the adipocytes increase in size up to 100 microns, probably due to the alteration of the sodium and potassium, allowing for free transport of extracellular liquid to the intracellular atmosphere. This observation is in agreement with those of Badin.

For higher energy settings, rupture of adipocytes, collagen fibres and small vessels were observed with reorganisation of the reticular dermis as well as coagulation of the collagen fibres in the fat tissue. Because of the rupture of the adipocyte membranes, lipases are liberated that are responsible for the liquefaction of the tissue, which further facilitates subsequent aspiration. Furthermore, the elevated number of passes performed to deposit the total amount of power causes unbridling of the fat tissue prior to a complementary aspiration. The fact that coagulation of small vessels is achieved reduces bleeding in the technique as well as the appearance of haematomas and subsequent bleeding. This could be of great benefit in large liposuctions by minimising the haemodynamic risks and affectations.

The appearance of:

- Degeneration of the adipocyte cell membranes
- Vaporisation
- Liquefaction
- Carbonisation
- Heat-coagulated collagen fibres

Are full dose-dependent.

Referring to studies by Kim, Geronemus and Goldman, it seems that the existence of tumescent infiltration does not affect the lipolysis effectiveness.

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