Novel Implantable Biosensors For Lifetime-based Monitoring Of Oxygenation To Predict Wound Healing
Preet Patel1, Mahmoud Ibrahim2, Ryan Schweller2, Bruce Klitzman2, Mohamid Ibrahim2.
1Duke University School of Medicine, Durham, NC, USA, 2Duke University Department of Surgery, Duke University Medical Center, Durham, NC, USA.
PURPOSE: Free-tissue-transfer requires close postoperative-monitoring to rapidly identify vascular-occlusion in order to improve salvage. It is estimated that 6%- 25% of skin flaps require a secondary surgical exploration and ~10% of flaps fail. Currently, all monitoring methods have limitations and impose a significant delay between time of vessel-occlusion and its detection. The scope of this study is to introduce a long-term, real-time method of vascular-occlusion through the observation of sensor-modulation in response to vascular-manipulation. METHODS: Experimental sensors were made by incorporating benzo-porphyrin dye into a matrix of Poly-Ethylene-Glycol-Diacrylate hydrogel, with each measuring 3mm-long,1.5mm-wide,0.5mm-thick. Using Sprague-Dawley rats (n=8), superficial-inferior-epigastric-artery myocutaneous flaps on the ventral abdomen and modified caudal MacFarlane-type random-flaps were surgically-elevated. Experimental oxygen sensors were intradermally implanted at the tip, middle and base of the flap-site. Tissue oxygen tension (TOT) readings were obtained from implanted sensors both at baseline and during vascular-clamping of feeding blood vessels. FiO2 modulation with sensor reading, perfusion analysis using sodium-fluorescein, gross-flap-analysis and statistical-analysis utilizing ANOVA were performed to evaluate sensor-efficacy across surgical-flaps. RESULTS: TOT was quantified and expressed after normalizing the oxygen to a reference arm. TOT measurements from the sensors were observed to modulate as anticipated by a magnitude that reflected the changes in inspired oxygen levels. Clinical observation of the flaps did not show any significant change in color and temperature of the flaps during or immediately after clamping of the feeding blood vessels. Real-time analysis of the sensors implanted in the myocutaneous flaps has demonstrated that acute vascular-clamping of feeding blood-vessels in the pedicle were immediately detected within 70-seconds.(*p<0.05) CONCLUSION: Oxygen-monitoring in tissues is highly sensitive and can be specific for the detection of acute vascular-occlusion/wound-healing. This approach is superior to clinical observation, faster than current standard of care methods and offers a cost-effective, accurate means of monitoring free-tissue-transfers.
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