A Novel Technology for Free Flap Monitoring: Pilot Study of a Wireless, Biodegradable Sensor

Abstract

Background Accurate monitoring of free flap perfusion after complex reconstruction is critical for early recognition of flap compromise. Surgeons use a variety of subjective and objective measures to evaluate flap perfusion postoperatively. However, these measures have some limitations. We have developed a wireless, biodegradable, and flexible sensor that can be applied to real-time postoperative free flap monitoring. Here we assess the biocompatibility and function of our novel sensor.

Methods Seven Sprague–Dawley (SD) rats were used for biocompatibility studies. The sensor was implanted around the femoral artery near the inguinal ligament on one leg (implant side) and sham surgery was performed on the contralateral leg (control side). At 6 and 12 weeks, samples were harvested to assess the inflammation within and around the implant and artery. Two animals were used to assess sensor function. Sensor function was evaluated at implantation and 7 days after the implantation. Signal changes after venous occlusion were also assessed in an epigastric artery island flap model.

Results In biocompatibility studies, the diameter of the arterial lumen and intima thickness in the implant group were not significantly different than the control group at the 12-week time point. The number of CD-68 positive cells that infiltrated into the soft tissue, surrounding the femoral artery, was also not significantly different between groups at the 12-week time point. For sensor function, accurate signaling could be recorded at implantation and 7 days later. A change in arterial signal was noted immediately after venous occlusion in a flap model.

Conclusion The novel wireless, biodegradable sensor presented here is biocompatible and capable of detecting arterial blood flow and venous occlusion with high sensitivity. This promising new technology could combat the complications of wired sensors, while improving the survival rate of flaps with vessel compromise due to its responsive nature.

Keywords

free flap monitoring - venous occlusion - microsurgery sensor - inflammation

• References

• 1 Disa JJ, Cordeiro PG, Hidalgo DA. Efficacy of conventional monitoring techniques in free tissue transfer: an 11-year experience in 750 consecutive cases. Plast Reconstr Surg 1999; 104 (01) 97-101
• 2 Kääriäinen M, Halme E, Laranne J. Modern postoperative monitoring of free flaps. Curr Opin Otolaryngol Head Neck Surg 2018; 26 (04) 248-253
• 3 Chae MP, Rozen WM, Whitaker IS. , et al. Current evidence for postoperative monitoring of microvascular free flaps: a systematic review. Ann Plast Surg 2015; 74 (05) 621-632
• 4 Furnas H, Rosen JM. Monitoring in microvascular surgery. Ann Plast Surg 1991; 26 (03) 265-272
• 5 Karinja SJ, Lee BT. Advances in flap monitoring and impact of enhanced recovery protocols. J Surg Oncol 2018; 118 (05) 758-767
• 6 Kroll SS, Schusterman MA, Reece GP. , et al. Timing of pedicle thrombosis and flap loss after free-tissue transfer. Plast Reconstr Surg 1996; 98 (07) 1230-1233
• 7 Bradford CR. Flap monitoring. Facial Plast Surg 1996; 12 (01) 19-21
• 8 Perng CK, Ma H, Chiu YJ, Lin PH, Tsai CH. Detection of free flap pedicle thrombosis by infrared surface temperature imaging. J Surg Res 2018; 229: 169-176
• 9 Oliver DW, Whitaker IS, Giele H, Critchley P, Cassell O. The Cook-Swartz venous Doppler probe for the post-operative monitoring of free tissue transfers in the United Kingdom: a preliminary report. Br J Plast Surg 2005; 58 (03) 366-370
• 10 Paydar KZ, Hansen SL, Chang DS, Hoffman WY, Leon P. Implantable venous Doppler monitoring in head and neck free flap reconstruction increases the salvage rate. Plast Reconstr Surg 2010; 125 (04) 1129-1134
• 11 Lenz Y, Gross R, Penna V, Bannasch H, Stark GB, Eisenhardt SU. Evaluation of the implantable Doppler probe for free flap monitoring in lower limb reconstruction. J Reconstr Microsurg 2018; 34 (03) 218-226
• 12 Warner KG, Durham-Smith G, Butler MD, Attinger CE, Upton J, Khuri SF. Comparative response of muscle and subcutaneous tissue pH during arterial and venous occlusion in musculocutaneous flaps. Ann Plast Surg 1989; 22 (02) 108-116
• 13 Chen Y, Shen Z, Shao Z, Yu P, Wu J. Free flap monitoring using near-infrared spectroscopy: a systemic review. Ann Plast Surg 2016; 76 (05) 590-597
• 14 Koolen PG, Vargas CR, Ho OA. , et al. Does increased experience with tissue oximetry monitoring in microsurgical breast reconstruction lead to decreased flap loss? The learning effect. Plast Reconstr Surg 2016; 137 (04) 1093-1101
• 15 Salgarello M, Pagliara D, Rossi M, Visconti G, Barone-Adesi L. Postoperative monitoring of free DIEP flap in breast reconstruction with near-infrared spectroscopy: variables affecting the regional oxygen saturation. J Reconstr Microsurg 2018; 34 (06) 383-388
• 16 Berggren-Olsen MM, Rauff-Mortensen A, Holst R, Houlind KC, Birke-Sørensen H. Monitoring of free flaps with combined tissue spectrophotometry and laser doppler flowmetry in an animal experimental model. J Reconstr Microsurg 2017; 33 (08) 579-586
• 17 Hölzle F, Loeffelbein DJ, Nolte D, Wolff KD. Free flap monitoring using simultaneous non-invasive laser Doppler flowmetry and tissue spectrophotometry. J Craniomaxillofac Surg 2006; 34 (01) 25-33
• 18 Boutry CM, Beker L, Kaizawa Y. , et al. Biodegradable and flexible arterial-pulse sensor for the wireless monitoring of blood flow. Nat Biomed Eng 2019; 3 (01) 47-57
• 19 Plock JA, Schnider JT, Schweizer R. , et al. The influence of timing and frequency of adipose-derived mesenchymal stem cell therapy on immunomodulation outcomes after vascularized composite allotransplantation. Transplantation 2017; 101 (01) e1-e11
• 20 Berthelot M, Yang GZ, Lo B. A self-calibrated tissue viability sensor for free flap monitoring. IEEE J Biomed Health Inform 2018; 22 (01) 5-14
• 21 Poder TG, Fortier PH. Implantable Doppler in monitoring free flaps: a cost-effectiveness analysis based on a systematic review of the literature. Eur Ann Otorhinolaryngol Head Neck Dis 2013; 130 (02) 79-85
• 22 Kempton SJ, Poore SO, Chen JT, Afifi AM. Free flap monitoring using an implantable anastomotic venous flow coupler: analysis of 119 consecutive abdominal-based free flaps for breast reconstruction. Microsurgery 2015; 35 (05) 337-344
• 23 Chowdhury SS, Hyder R, Hafiz MSB, Haque MA. Real-time robust heart rate estimation from wrist-type ppg signals using multiple reference adaptive noise cancellation. IEEE J Biomed Health Inform 2018; 22 (02) 450-459
• 24 Huang S-C, Hung P-H, Hong C-H, Wang H-M. A new image blood pressure sensor based on PPG, RRT, BPTT, and harmonic balancing. IEEE Sens J 2014; 14 (10) 3685-3692
• 25 Chao PC, Chiang PY, Kao YH. , et al. A portable, wireless photoplethysomography sensor for assessing health of arteriovenous fistula using class-weighted support vector machine. Sensors (Basel) 2018; 18 (11) E3854
• 26 Chiang P-Y, Chao PC-P, Tarng D-C, Yang C-Y. A novel wireless photoplethysmography blood-flow volume sensor for assessing arteriovenous fistula of hemodialysis patients. IEEE Trans Ind Electron 2017; 64 (12) 9626-9635
• 27 Kind GM, Buntic RF, Buncke GM, Cooper TM, Siko PP, Buncke Jr HJ. The effect of an implantable Doppler probe on the salvage of microvascular tissue transplants. Plast Reconstr Surg 1998; 101 (05) 1268-1273 , discussion 1274–1275