Critical Ischemia Time, Perfusion and Drainage Function of Vascularized Lymph Nodes

BACKGROUND Vascularized lymph node transfer is a promising surgical treatment for lymphedema. This study investigates the effect of ischemia on the lymphatic drainage efficiency of vascularized lymph node flaps and the critical ischemia time of lymph nodes. METHODS Twenty-four lymph nodes containing groin flaps in twelve Sprague-Dawley rats were dissected. Clamping of the vascular pedicle was performed for 0, 1, 3, 5, 6, 7 hours, then each allowed to re-perfuse via the vascular pedicle for one hour. Perfusion and ischemic changes were assessed using indocyanine green lymphography, laser Doppler flowmetry, and histological studies with associated LYVE-1, CD68, DAPI, TUNEL and GSH assay stains. RESULTS The mean latency period of the groin lymph node flaps was 247±67, 83±15, 72±42, 30±18, and 245±85 seconds in the 0-, 1-, 3-, 5- and 6-hour groups, respectively. Perfusion detected by laser Doppler was 85.2±14.5, 87.2±36.7, 129.8±33.7, 140.4±148.5, 156.1±91.4 and 41.2±34.8 perfusion units at ischemia times of 0, 1, 3, 5, 6, and 7 hours, respectively. Cell damage measured by glutathione was 46.8±10.2, 67.7±14.2, 62.8±15.4, 126.6±5.9, 259.0±70.3, and 109.1±27.5 at ischemia times of 0, 1, 3, 5, 6, and 7 hours, respectively. Histologically, as ischemia time increased, hemorrhage and congestion became more severe. CONCLUSIONS The critical ischemia time of vascularized lymph nodes is five hours in the rodent animal model, verified by ICG lymphatic fluid uptake, laser Doppler perfusion, and histologic assessments. Interestingly, lymphatic drainage and perfusion of vascularized lymph nodes were improved with an increased ischemia time before the critical five hours was reached. # These authors contributed equally. Co-first authors. Disclosures: None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this manuscript. Presented at: 9th Congress of World Society for Reconstructive Microsurgery, Seoul, Korea, June 16, 2017 and 2018 American Society of Reconstructive Microsurgery, Phoenix, Arizona, USA; January 15, 2018. Corresponding Author: Hui-Yi Hsiao, Ph.D., Center for Tissue Engineering, Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, 5, Fu-Hsing Street, Kueishan, Taoyuan 333, Taiwan., Tel.: +886-3-3281200 #2560, Fax: +886-3-3970370, E-mail address: ivyhsiao@gmail.com, ivyhsiao@cgmh.org.tw ©2018American Society of Plastic Surgeons

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