Negative pressure-induced hyperemia, a new modality in the monitoring of skin paddle containing free flaps

Background: In free tissue transfer, monitoring is paramount to timely detect vascular complications. Although various technical methods have been introduced, clinical flap monitoring and, particularly, capillary refill test (CRT) remain the gold standard. In pale flaps, CRT is challenging as it relies on the color difference between blanched and perfused skin. We proposed a new method of negative pressure-induced hyperemia (NPIH) using handheld electrical negative pressure devices to improve flap monitoring. Methods: Forty consecutive patients who received 42 free flaps in our institution were included in the study. Postoperatively, digital photographs were taken during CRT and NPIH, and the color difference (Delta E) was calculated based on the images. Additionally, three surgeons and three nurses evaluated the ease of assessment of capillary refill and NPIH on each flap using five grades. Results: NPIH yielded a significantly higher color difference than CRT with a mean Delta E of 10.3 +/- 3.3 versus 6.8 +/- 4.2. Although for CRT, Delta E of 14 flaps was <5 and of seven flaps <3, all flaps had a Delta E of >5 for NPIH. Subjectively, both surgeons and nurses found NPIH in all flaps to be easier to assess with a mean score of 1.1 +/- 0.3 versus 1.8 +/- 1.1 for CRT. However, some flaps were found to be challenging or not assessable by CRT. Conclusion: NPIH represents a safe, easily applicable, and cheap addition to the established clinical and technical examination methods and may offer advantages over conventional CRT in detecting arterial complications in pale flaps. (C) 2019 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.