Can the green laser Doppler measure skin-nutritive perfusion in patients with peripheral vascular disease

The recently developed green laser (GL; wavelength 543 nm) is thought to me asure perfusion derived from a more superficial skin layer than does the st andard near-infrared laser (RL; wavelength 780 nm). These lasers were used to investigate the disturbances in the different layers of skin perfusion i n ischaemic legs before and after treatment and compared with capillary mic roscopy. Eighteen patients (20 legs) with different stages of leg ischaemia scheduled for a vascular intervention (11 males, 7 females; median age 73, range: 52-81 years; Fontaine stages II-IV) were investigated by means of c apillary microscopy, visualising the nail fold capillary perfusion, and a l aser Doppler, equipped with a special dual probe conducting both GL and RL. The probe was attached to the pulp and the dorsum of the big toe to assess skin perfusion at rest and during reactive hyperaemia, while sitting and w hile supine. Resting and hyperaemic perfusion using GL was low and signific antly lower (p < 0.01) than with RL in both areas and positions. Laser Dopp ler perfusion was higher in the pulp than on the dorsum with both wavelengt hs (p < 0.05). The hyperaemia response was highest using GL and differed am ong the three techniques. Postural reduction of capillary and RL flow was r educed, but not with GL. After treatment, skin capillary perfusion improved more clearly than did the laser Doppler perfusion with either wavelength, while postural vasoconstriction improved only when measured with the capill ary microscope. The differences found between RL and GL Doppler perfusion, but also between GL and capillary microscopy measurements suggest that the GL does measure the more superficial, but not exclusively the nutritive ski n perfusion. Clinically, the use of the green laser in its present form in patients with leg ischaemia offers no advantage over the red laser. Copyrig ht (C) 2000 S. Karger AG. Basel.