Monitoring of Free Flaps with Combined Tissue Spectrophotometry and Laser Doppler Flowmetry in an Animal Experimental Model

Background Success of free tissue transfer depends on standardized intraoperative flap design, microsurgical technique, and postoperative monitoring. We sought to investigate whether laser speckle imaging (LSI) is suitable for optimization of intraoperative flap design and postoperative monitoring of free flaps with skin paddles. Methods Skin perfusion was assessed with LSI in 27 free flaps after dissection at the donor site, after anastomosis at the recipient site, after inset and on postoperative days (POD) 1, 5, and 10. Skin perfusion of the whole flap (ROI [region of interest]-1) and the area over the pedicle (ROI-2) were compared between patients with and without postoperative complications (POC+ and POC − , respectively). A receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff for perfusion during LSI-guided microsurgery. Results In flaps without or only minor POC, intraoperatively measured perfusion over ROI-2 was significantly higher compared with ROI-1, whereas no significant differences were found for flaps with major POC. Perfusion of ROI-1 and 2 intraoperatively and on POD 1 was significantly lower in the POC+ compared with the POC− group (p < 0.05). ROC analysis yielded a threshold of 107 perfusion units (PU) at ROI-2 with an area under the curve (AUC) of > 0.8 for identification of flaps with major POC. Conclusion LSI is an easy to use, noninvasive technique for identification of malperfused areas in free flaps, thus allowing for intraoperative decision-making on flap dimensions and postoperative monitoring. LSI therefore is a valuable tool for perfusion assessment with a high potential to become an established part of microsurgical practice.

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Continuous Video-Rate Laser Speckle Imaging for Intra- and Postoperative Cutaneous Perfusion Imaging of Free Flaps

Rauh

Henn

Nagel

et al. 2019

J reconstr Microsurg

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

Oda

Beker

Kaizawa

et al. 2019

J Reconstr Microsurg

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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.

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Faster Detection of Ischemia in Free Muscle Transfer When Using Microdialysis

Rauff-Mortensen

Berggren-Olsen

Kirkegaard

et al. 2019

J reconstr Microsurg

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Background Microdialysis is a clinical method used to detect ischemia after microvascular surgery. Microdialysis is easy to use and reliable, but its value in most clinical settings is hampered by a 1- to 2-h delay in the delivery of patient data. This study evaluated the effectiveness of an increase in the microdialysis perfusion rate from 0.3 to 1.0 µL/min on the diagnostic delay in the detection of ischemia. Methods In eight pigs, two symmetric pure muscle transfers were dissected based on one vascular pedicle each. In each muscle, two microdialysis catheters were placed. The two microdialysis catheters were randomized to a perfusion rate of 0.3 or 1.0 µL/min, and the two muscle transfers were randomized to arterial or venous ischemia, respectively. After baseline monitoring, arterial and venous ischemia was introduced by the application of vessel clamps. Microdialysis sampling was performed throughout the experiment. The ischemic cutoff values were based on clinical experience set as follows: CGlucose < 0.2 mmol/L, CLactate > 7 mmol/L, and the lactate/pyruvate ratio > 50. Results The delay for the detection of 50% of arterial ischemia was reduced from 60 to 25 minutes, and for the detection of all cases of arterial ischemia, the delay was reduced from 75 to 40 minutes when the perfusion rate was increased from 0.3 to 1.0 µL/min. After the same increase in perfusion, the detection of 50% of venous ischemia was reduced from 75 to 40 minutes, and for all cases of venous ischemia, a reduction from 135 to 95 minutes was found. Conclusion When using microdialysis for the detection of ischemia in pure muscle transfers, an increase in the perfusion rate from 0.3 to 1.0 µL/min can reduce the detection delay of ischemia.

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Monitoring of Free Flaps with Combined Tissue Spectrophotometry and Laser Doppler Flowmetry in an Animal Experimental Model

Cited by 4 publications

References 20 publications

Continuous Video-Rate Laser Speckle Imaging for Intra- and Postoperative Cutaneous Perfusion Imaging of Free Flaps

Continuous Video-Rate Laser Speckle Imaging for Intra- and Postoperative Cutaneous Perfusion Imaging of Free Flaps

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

Faster Detection of Ischemia in Free Muscle Transfer When Using Microdialysis

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