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

Abstract Background In free tissue transfer, monitoring is paramount to timely detect vascular complications. While various technical methods have been introduced, clinical flap monitoring and here particularly capillary refill testing (CRT) remains the gold standard. In pale flaps, CRT is challenging as it relies on the color difference between blanched and perfused skin. We propose a new method of negative pressure induced hyperemia (NPIH) using handheld electrical negative pressure devices to improve flap monitoring. Methods 40 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 color difference ΔE was calculated on the images. Additionally, three surgeons and three nurses evaluated 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 ΔE of 10.3±3.3 versus 6.8 ±4.2. While for capillary refill testing ΔE of 14 flaps was 5 for NPIH. Subjectively, both surgeons and nurses found NPIH to be easier to assess with a mean score of 1.1±0.3 versus 1.8±1.1 for CRT. While some flaps were found to be challenging or not assessable by CRT, all examiners evaluated NPIH in all flaps as easy to assess. 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.