Evaluation of Total vs. Regional Blood Perfusion with a Laser Doppler Imaging System in the Rat Epigastric Flap

ABSTRACT

Monitoring systems to measure flap survival are either invasive, touch the surface of the tissue, or have problems in reproducibility. The authors sought to determine the efficacy of a laser Doppler imaging (LDI) system to measure perfusion in a myocutaneous flap, by producing a two-dimensional picture of the flap without touching the surface. They compared total flap perfusion with perfusion in selected areas of interest after flap surgery. The perfusion in the left groin of Sprague-Dawley rats was measured before and after surface rubbing, skin injury, and during different lighting conditions. The perfusion of the epigastric flap before and over a period of 60 min after elevation was measured, and values were compared to pre-surgical values and to sham-operated animals. They determined the differences between single and running-suture techniques after flap surgery, as well as between venous and/or arterial occlusion.

Surface rubbing, skin injury, and light influenced the LDI image. After flap elevation, total flap perfusion remained stable, while the distal area (area 8, n = 7) of the flap showed a statistically significant decrease in perfusion (71 ± 5.9 vs. 92 ± 9.5 percent perfusion units-PU; p < .05). The proximal areas (1 to 3, n = 7) of the flap had a higher perfusion at 60 min after flap surgery, compared with sham-operated (n = 8) animals (118 ± 12.5 vs. 97 ± 10.4 percent PU; p < .05). The running-suture technique was followed by decreased perfusion on the peripheral side of the flap, compared with the single-suture technique (73.7 ± 9.2 vs. 99.2 ± 4.9 percent PU; n = 2). The LDI was able to visualize venous and/or arterial occlusion after flap surgery.

Under standardized circumstances (light, temperature), the LDI was efficient in measuring regional flap circulation experimentally. While total flap perfusion after flap surgery remained stable, perfusion in the distal flap decreased significantly.

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