Long Pulsed Nd:YAG Lasers

4.2.3.1 Vascular Application

When treating vascular issues with light-based technology, the depth of the vessel plays a major role in the decision of which technology to use. Superficial facial vessels are gener­ally smaller in size, and closer to the surface of the skin, and as a result, are easily treated by highly absorbed wavelengths in the 480-670 nm range. When deeper, larger vessels, usually in the leg area, are the target, those shorter wavelengths mentioned earlier cannot achieve deep enough penetration. This is due to the amount of competing chromophores at those wavelengths, namely melanin. The key in treating these deeper vessels is to utilize a wavelength that has some selectivity for oxyhemoglobin, but lacks the competing chro­mophores present at the shorter wavelengths. Long pulsed Nd:YAG lasers at 1,064 nm are the perfect fit.

The Nd:YAG laser is ideal for treating larger, deeper vessels up to 3-4 mm. This wave­length combines some selectivity for absorption in oxyhemoglobin, while not having the high level of competing chromophores present at the lower 400-700 nm wavelengths. This gives the YAG laser the ability to penetrate deep enough into the skin to treat deeper vessels that previously required painful injections known as sclerotherapy. This allows operators to treat deep vessels with a laser treatment that leaves the patient with a relatively minor urti­carial histamine type response that dissipates over the two weeks posttreatment.

Although many patients seek treatment of facial vessels, the YAG laser is not the opti­mal tool for this procedure. Although effective on some of the larger vessels, the YAG laser presents a new problem not encountered in the lower wavelengths, water absorption.

At 1,064 nm, there is an elevated level of water absorption, and because the skin in the nasal area has such a high water content, the high absorption coefficient will pull the laser deeper into the skin than desired. This elevated light absorption, combined with the lack of competing chromophores may result in a burn, a change in pigmentation, and in the worst cases, a permanent, depressed scar. These facial vessels can be much more effi­ciently and safely treated using systems in the lower wavelength range (pulsed dye or pulsed light with contact cooling).

The characteristics that make the YAG inefficient and dangerous for treating facial telangiectasias actually make it ideal for treating leg veins. Leg vessels by nature are usu­ally larger and deeper than facial vessels, so a system is needed that can penetrate deep enough to selectively target such a vessel. The YAG utilizes a spot size that corresponds to the vessel size, and is then moved along the vessel, firing every few millimeters depending on the vessel size. As with other vascular treatments, pulse duration and fluence are adjusted according to the size as well, the larger the vessel, the longer the pulse duration will be, and higher the fluence. One pass should be sufficient (Fig. 4.5), but in many of the more extreme cases, a second pass may be necessary. Never stack the pulses on top of one another, as this is a sure way to cause a complication. The endpoint should be an urticarial histamine-type (raised red cat scratch) response, and although some vessels may close at the time of treat­ment, not seeing the closure does not always warrant a second pass. Vessels up to 4 mm can be treated with the laser alone, but in the case of larger vessels, proper treatment requires a combination of YAG and injection therapy (sclerotherapy).

Immediately after treatment, cooling is essential to reduce the inflammation and the risk of thermal injury, and a topical steroid may be used to resolve any blistering issues. Com­pression stockings may be worn for 1-2 weeks posttreatment, and some light walking and exercise is essential to resolve the majority of these lower extremity vascular issues. In case of blood pooling, lancing with an 18-gauge needle is sufficient to remove excess blood, and using a 500-700 nm pulsed light hand piece with contact cooling, such as the Palomar Starlux with the Lux G hand piece, will help to resolve most hemosiderin staining issues. Treatments should be every 6-8 weeks, and most cases should be resolved in three to six treatment sessions.