Transcutaneous oxygen measurement using ratiometric fluorescence imaging as a valid method for monitoring free flap transplants

Abstract

Background: Reconstruction of soft tissue defects with free flaps is a common procedure in plastic and reconstructive surgery. Most postoperative complications occur within the first 48-72 hours after surgery. After postoperative complications, short perfusion restoration times may improve flap survival rates by up to 30-50%. Ratiometric fluorescence imaging is an additional or alternative method of postoperative flap monitoring.

Objective: To test the efficacy and utility of transepidermal oxygen flux imaging to evaluate postoperative skin oxygenation of free and local flaps in the first 48 hours after surgery.

Methods: The study included 32 patients (aged between 18 and 80 years; mean age 52.9) with a tissue defect covered with a free flap transplant at the Department of Plastic and Reconstructive Surgery of the University Medical Center Regensburg. Postoperative oxygen flux was measured with the 'VisiSens system' placed on the vascular pedicle as well as on the peripheral and central part of the flap.

Results: Values of oxygen flux were higher in case of flap congestion (0.069±0.012) or flap necrosis (0.155±0.083) than in cases without any complications (0.061±0.006). Flux values of different areas of the same flap showed only minimal differences (central part: 0.065±0.008, peripheral part: 0.070±0.009, vascular pedicle: 0.056±0.004); the level of significance was p = 0.904.

Conclusion: Imaging transepidermal oxygen flux by ratiometric luminescence seems to be a reliable alternative, indirect method of postoperative flap monitoring with regard to microcirculatory function and flap viability.

Keywords: Postoperative free flap monitoring; flap monitoring; flux imaging; microcirculatory function; tissue oxygenation; tissue perfusion; transcutaneous oxygen measurement.