Comparison of Hyperspectral Imaging and Microvascular Doppler for Perfusion Monitoring of Free Flaps in an In Vivo Rodent Model

Abstract

To reduce microvascular free flap failure (MFF), monitoring is crucial for the early detection of malperfusion and allows timely salvage. Therefore, the aim of this study was to evaluate hyperspectral imaging (HSI) in comparison to micro-doppler sonography (MDS) to monitor MFF perfusion in an in vivo rodent model. Bilateral groin flaps were raised on 20 Sprague–Dawley rats. The femoral artery was transected on the trial side and re-anastomosed. Flaps and anastomoses were assessed before, during, and after the period of ischemia every ten minutes for overall 60 min using HSI and MDS. The contralateral sides’ flaps served as controls. Tissue-oxygenation saturation (StO2), near-infrared perfusion index (NPI), hemoglobin (THI), and water distribution (TWI) were assessed by HSI, while blood flow was assessed by MDS. HSI correlates with the MDS signal in the case of sufficient and completely interrupted perfusion. HSI was able to validly and reproducibly detect tissue perfusion status using StO2 and NPI. After 40 min, flap perfusion decreased due to the general aggravation of hemodynamic circulatory situation, which resulted in a significant drop of StO2 (p < 0.005) and NPI (p < 0.005), whereas the Doppler signal remained unchanged. In accordance, HSI might be suitable to detect MFF general complications in an early stage and further decrease MFF failure rates, whereas MDS may only be used for direct complications at the anastomose site.

Bone reconstruction of extensive maxillomandibular defects in adults

“…These techniques require advanced skills, technology, infrastructure, and materials 170 . However, relevant donor site morbidity, a notable rate of flap complications, including transplant losses, were described 176–178 …”

“…170 However, relevant donor site morbidity, a notable rate of flap complications, including transplant losses, were described. [176][177][178] Mostly, grafts from the fibula, the iliac crest, and the scapula are used for bone reconstruction of large bone defects. Each donor site offers unique characteristics, including of large bone defects and soft tissue, quality, and specific donor site morbidity.…”

Hyperspectral imaging for monitoring of free flaps of the oral cavity: A feasibility study

“…Besides relying on the absolute value given, it is definitely of upmost importance to analyze the perfusion parameters over time, especially because there is a large variation already in the baseline data. Several studies have pointed out the importance of including the drop rate when evaluating indices acquired from spectral imaging, 18,19,30,31 even though a cut-off between physiologic and pathologic changes has yet to be defined. Within the present study, for NIR Perfusion Index no patient had a decrease of >35% of the baseline value (more than 20 points) at t1.…”

Attached compared with unattached surface probes for monitoring flap perfusion in microvascular head and neck reconstruction: a feasibility study

“…Since anastomotic compromise occurs in approximately 10% of all cases and timely recognition and intervention are the most important factors for successful flap salvage, regular postoperative assessment of flap viability is crucial for microvascular free tissue transfer 1 , 5 – 8 . The standard clinical assessment of flap viability, which considers parameters such as flap surface color, temperature, and capillary refill, faces complications due to delayed external signs of impaired flap perfusion and the natural paleness of flaps, and is also subjective in nature, requiring experienced personnel who may not always be available 1 , 4 , 9 , 10 . Therefore, technical methods for flap monitoring, such as the oxygen-to-see (O2C) analysis system (LEA Medizintechnik, Germany), have been developed 1 , 11 .…”