In treating the port wine stain type of haemangioma, the use of cover by cosmetics, and surgical removal, have been the unavoidable mainstays despite their manifest inadequacy, but the development of laser technology has now added a third therapeutic possibility. Two main types of laser are currently used, argon and tuneable dye lasers.
Both instruments work on the principle
that energy emitted by the laser is absorbed by the oxyhaemoglobin in erythrocytes within the ectatic vessels of the haemangioma. Diffusion of this energy damages the endothelial cells of the vessels and they undergo fibrosis. Circulation through the vessels ceases, and the port wine appearance is lost. With both types of laser, the end result of treatment is largely the same, but they reach it in different ways.
The argon laser emits blue-green light, with
most of the energy at 488 and 514 nm. Using a
1 mm laser beam spot, the dermis is penetrated to a depth of 0.75-1 mm. The energy of each pulse, though it is applied in very short pulses of 200 µs, tends to be dissipated beyond the blood vessels into surrounding tissues, giving rise on occasion to a degree of scarring. Focal alopecia can also occur.
The area of staining is treated in such a way as to produce a confluent patch, but up to 2 months have to be allowed so that the tissues can recover before treatment of a skin area adjacent to a previously treated site can be carried out.
The tuneable dye laser uses a rhodamine dye source, and emits light at 585 nm. Oxyhaemoglobin has an absorption peak at
577 nm, and the nearness of the two gives it the advantage over the argon laser of increased specificity, and penetration of the dermis to a greater depth, 1-1.5mm. As a result, the risk of scarring is low. In contrast to the argon laser, non-contiguous areas are treated with a 5 mm laser spot. This initially produces a purpuric patch of skin, which reverts to a normal skin colour within a fortnight.
Successive treatments are aimed at intervening residual areas of staining.
Regardless of which laser is used, multiple treatments are required at intervals of roughly
2 months to allow the tissues to recover. The comparative merits of the two types of laser are difficult to quantify.
Clinical experience suggests that the argon laser produces better results in dark port wine stains, while the tuneable dye laser is more effective in treating paler lesions, particularly in children.
In the older patient, the haemangioma tends to extend superficially, and in depth.
Superficial extension has the effect of creating increasing irregularity of its surface; extension deeply usually brings the lesion beyond the limit of penetration, and as a result it does not respond well to laser therapy.
‘Amateur’ tattoos, produced with Indian ink, have been found to respond well to treatment using the Q-switched ruby laser. Some, though not invariable, success has also been achieved
in treatment of traumatic tattooing. With 3 J at
694 nm delivered in a 30 ms pulse, with a spot size of 5 mm, the effect is confined to the carbon pigment, which is converted to colourless oxides. Carried out under local anaesthesia, the vasoconstriction of added adrenaline has the effect of minimising any interaction between the blood and the laser beam. Improvement has also been found to occur in dark professional tattoos.
The carbon component is removed, but unexpectedly significant fading of the red and green pigment has also occurred. This is felt to be the result of enhanced phagocytic activity, induced as part of the effect on the carbon component of the tattoo.
Laser technology is a rapidly expanding and
developing field in medical physics.
Protagonists claim considerable improvement in problem areas such as removal of hair (following flap transfer) and resolution of hypertrophic scars. These treatments remain to be proved in clinical practice and have not, as yet, been adopted widely.