Near-Infrared Spectroscopy Measures Tissue Oxygenation in Free Flaps for Breast Reconstruction

Sir: Breast reconstruction is commonly performed after mastectomy for breast cancer. Myocutaneous or fasciocutaneous flaps reliably replace and closely approximate the look and feel of breast tissue. However, both free and pedicled flaps are subject to vaso-occlusive events resulting in flap necrosis. In large series, total free flap failure rates have been estimated to be at least 4 percent.1 Early detection of vascular events is paramount to flap salvage. More than 90 percent of surgeons use adjunctive objective monitoring devices to supplement clinical assessment.1 Current monitoring devices fall short of the ideal device proposed by Jones,2 and no single device is accepted for routine monitoring. Since tissue oxygen tension is a sensitive tool with which to assess muscle microcirculation, we have been using the ViOptix ODISsey tissue oximeter, which utilizes near-infrared spectroscopy technology, to monitor free flaps in the operating room and immediate postoperative recovery period (Fig. 1).Fig. 1.: Real-time noninvasive monitoring of free flaps. In this patient, the ODISsey tissue oximeter probe is attached to the free transverse rectus abdominis myocutaneous flap for postoperative monitoring.In seven consecutive free flaps performed for breast reconstruction at Stanford University, tissue oxygen tension measurements were taken at baseline, after flap elevation, with clamping of inflow vessels and after vessel anastomosis, after flap insetting, and in postoperative recovery. Simultaneously, clinical parameters and Doppler checks were performed every hour postoperatively for 24 to 48 hours. Our baseline tissue oxygen tension measurements averaged 83 percent (range, 70 to 99 percent). After flap elevation, oxygen tension was unchanged in zone 1, but it typically dropped in zone 4 by 15 to 20 percent (average zone 4 tissue oxygenation, 64 percent). When the vessels were clamped to transfer the flap, tissue oxygen tension dropped an average of 33 percent (range, 25 to 38 percent). After vessel reanastomosis, tissue oxygen tension rapidly increased to approximate preclamping values within 5 minutes. A representative tracing is shown in Figure 2. Measurements remained stable for the next 48 hours, correlating with positive Doppler readings in all flaps. No fat or flap necrosis was noted at the first postoperative visit in any patient.Fig. 2.: Intraoperative and postoperative monitoring of free flaps with near-infrared spectroscopy. There was a significant drop in tissue oxygen tension (StO2) with clamping of the inflow vessels and a brisk increase in tissue oxygen tension with vessel anastomosis, reaching preclamping values in 5 to 10 minutes. These values were maintained throughout the recovery period and on postoperative days 1 and 2.Various objective methods of flap monitoring have been proposed to assist the clinical examination, but reliability depends on the training and experience of the nursing staff. Each method also has other limitations, so each microsurgeon adopts whichever technique he or she has the most experience with. Near-infrared spectroscopy offers the benefit of monitoring tissue oxygen tension noninvasively. The technology used in this study with the ViOptix tissue oximeter displays the saturation of oxygen on a touch-screen console, which can be followed continuously in the postoperative setting. Once the probe is placed on the patient, readings are independent of nursing expertise and clinical experience. Near-infrared spectroscopy technology has been shown to reliably track tissue oxygen tension in both animal and human models.3,4 We have shown good correlation with serial quantitative fluoroscopy and clinical outcome in the postoperative monitoring of digits following replantation.5 Although our series contained no total flap failures secondary to arterial or venous occlusion, predictable tissue oxygen changes were reliably detected with vessel clamping and reanastomosis for free flap transfers. No complications were associated with using the device. Therefore, measurement of tissue oxygenation with near-infrared spectroscopy may be a safe, reliable tool for postoperative monitoring of free flaps. Amy S. Colwell, M.D. Department of Surgery Division of Plastic Surgery Brigham and Women’s Hospital Harvard Medical School Boston, Mass. Leigh Wright, R.N. Yvonne Karanas, M.D. Department of Surgery Division of Plastic Surgery Stanford University Stanford, Calif.