Assessment of Skin Flaps Using Optically Based Methods for Measuring Blood Flow and Oxygenation

Abstract

The objective of this study was to compare two noninvasive techniques, laser Doppler and optical spectroscopy, for monitoring hemodynamic changes in skin flaps. Animal models for assessing these changes in microvascular free flaps and pedicle flaps were investigated. A 2 x 3-cm free flap model based on the epigastric vein-artery pair and a reversed MacFarlane 3 x 10-cm pedicle flap model were used in this study. Animals were divided into four groups, with groups 1 (n = 6) and 2 (n = 4) undergoing epigastric free flap surgery and groups 3 (n = 3) and 4 (n = 10) undergoing pedicle flap surgery. Groups 1 and 4 served as controls for each of the flap models. Groups 2 and 3 served as ischemia-reperfusion models. Optical spectroscopy provides a measure of hemoglobin oxygen saturation and blood volume, and the laser Doppler method measures blood flow. Optical spectroscopy proved to be consistently more reliable in detecting problems with arterial in flow compared with laser Doppler assessments. When spectroscopy was used in an imaging configuration, oxygen saturation images of the entire flap were generated, thus creating a visual picture of global flap health. In both single-point and imaging modes the technique was sensitive to vessel manipulation, with the immediate post operative images providing an accurate prediction of eventual outcome. This series of skin flap studies suggests a potential role for optical spectroscopy and spectroscopic imaging in the clinical assessment of skin flaps.

Results of monitoring fasciocutaneous, myocutaneous, osteocutaneous and perforator flaps: 4-year experience with 166 cases

“…This decrease in haemoglobin oxygenation despite higher perfusion might be explained by the higher oxygen consumption of the newly transplanted tissue. PAYETTE et al investigated microcirculation in DIEP flaps with laserDoppler flowmetry and lightguide reflectance spectrophotometry 21 . In their series of uncomplicated flaps, the oxygenated haemoglobin was also lower postoperatively compared with preoperative values.…”

“…The authors report the first monitoring device that allows non-invasive simultaneous measuring of quantitative blood flow and haemoglobin oxygenation 10,11,12,15,21 . It also identifies arterial occlusion and venous congestion, which is essential for increasing the success rate in free-flap transfer 8,16,19 .…”

Early reintervention of compromised free flaps improves success rate

“…8,9 Newer methods that have been developed for monitoring are tissue spectophotometry, laser Doppler flowmetry, and tissue oxygen pressure measuring probes. [10][11][12] Although the conventional techniques mentioned above are reliable in most flaps, they are not in buried flaps because of their external component. 3,13 To better monitor buried flaps implantable Doppler probes are available.…”

Monitoring for Upper-Extremity Free Flaps and Replantations

“…24 Near-infrared spectroscopy has been found to be more reliable for detecting arterial problems when compared with laser Doppler assessment and has been found efficacious in cases of digital replantation. 25,26 When is it safe to stop monitoring? Most free tissue transfers are lost within the first 3 days.…”