Effect of Skin Temperature on Selective Vascular Injury Caused by Pulsed Laser Irradiation

The effect of skin temperature on vascular-specific injury caused by pulsed laser irradiation was examined. Ten healthy human volunteers were exposed to 1.5 microsecond pulses from a dye laser tuned to 577 nm. Compared to normothermic conditions (33°C skin temperature) significantly more laser energy (p < 0.01) was required to produce grossly visible purpura when the skin was cooled to 20°C or heated to 40°C. Histologically, laser-induced damage was confined to blood vessels at all three skin temperatures studied. At purpura threshold dose, there was intravascular agglutination without extravasation of red blood cells at 20°C whereas at 33° and 40°C there was extravasation of red blood cells