Free flap monitoring using simultaneous non-invasive laser Doppler flowmetry and tissue spectrophotometry

Early identification of flap failure is an indispensable prerequisite for flap salvage. Although many methods of free flap monitoring are available, there is still no single reliable non-invasive technique for early recognition of flap failure and for differentiation between arterial occlusion and venous congestion. The aim of this study was to investigate the benefits of the tissue oxygen analysis system O(2)C for monitoring patients undergoing maxillofacial reconstruction with fasciocutaneous radial forearm flaps.

In a prospective clinical study the microcirculatory parameters of blood flow, flow velocity, haemoglobin concentration (AU, Arbitrary Units) and oxygen saturation (%) were assessed by clinical means, by laser Doppler flowmetry and tissue spectrophotometry in 61 patients intraoperatively. Measurements were carried out before flap harvest, in the separated radial forearm flap, immediately after anastomoses and up to 14 days after reconstruction.

Following anastomosis, blood flow and flow velocity exceeded the level before flap elevation and reached significant differences by the third postoperative day (p<0.05). Oxygen saturation decreased significantly by the third postoperative day and haemoglobin oxygenation showed stable values after performing anastomosis. Simultaneous, non-invasive laser-Doppler flowmetry and tissue spectrophotometry detected vascular complications in all cases with no false positive or false negative results and prior to clinical assessment.

For the first time this new device allows reliable prediction of venous congestion by an increase of haemoglobin-concentration, and of arterial occlusion by a decrease in blood flow parameters and oxygen saturation. It can thus differentiate the mechanisms of flap failure before clinical assessment.