THE EFFECTS OF DIODE LASER LLLT ON FLAP SURVIVAL: MEASUREMENT OF FLAP MICROCIRCULATION WITH LASER SPECKLE FLOWMETRY

Abstract

A laser speckle flowmetry technique has been developed to enable visualization of the distribution of skin blood flow and has been used to measure the microcirculation in various angiopathies as well as to monitor blood flow changes and other haemodynamics in skin flaps. The principal author's institute has recently acquired such a laser speckle flowmetry system. The present preliminary study was designed to test the efficacy of the gallium aluminium arsenide (GaAlAs) diode laser on flap survival in the rat model using laser speckle flowmetry. Caudal-based random pattern flaps were raised on the back of two groups of Wistar rats, 10 rats in each group. The first group served as the control and underwent sham irradiation, otherwise they were handled in exactly the same way as the second group. The blood flow in all flaps was measured with laser blood flowmetry using the laser speckle method. Blood flow was measured in the flaps of the experimental animals and the unirradiated controls preirradiation, and the flaps were sutured back in place. The experimental group received laser irradiation from a GaAlAs diode laser (60 mW, 830 nm, continuous wave) for one minute on a point at the centre of the flap base (energy density ≅ 36 J/cm2). Laser speckle flowmetry was then performed on all animals immediately postirradiation and 30 minutes postirradiation. The following points were noted. There was no significant change in the flow rate of the flaps in the unirradiated animals. Immediately following the one minute irradiation in the experimental animals a decrease in the blood flow rate was seen compared with the unirradiated controls, but at 30 minutes postirradiation the blood flow rate in the flaps increased in the irradiated animals compared with controls. Five days postirradiation the survival area of the diode laser irradiated flaps was greater than the control flaps (≅1.12 : 1). It was concluded that GaAlAs diode LLLT increased early perfusion of the experimental flaps, thereby possibly accelerating early stage wound repair while at the same time controlling the inflammatory response, thus giving the irradiated flaps a better and earlier ‘take’.