Tissue Oximetry Monitoring for Free Deep Inferior Epigastric Perforator Flap Viability: Factors to be Considered toward Optimizing Postoperative Outcome

Postoperative Monitoring of Free DIEP Flap in Breast Reconstruction with Near-Infrared Spectroscopy: Variables Affecting the Regional Oxygen Saturation

Tissue Oximetry for Monitoring Free DIEP Flap Viability: Factors to Consider towards Optimizing Postoperative Outcome

We would like to thank the authors for their insightful comments regarding our article.[1] We agree on the potential mismatch between the sensor size and the skin flap area related to misreading in near-infrared spectroscopy (NIRS) monitoring of flaps with small monitor islands, as we already discussed.

In our article we described the flap resection method using the intraoperative indocyanine infrared angiography (photodynamic eye [PDE]). Previously, Holm et al also applied indocyanine green in the deep inferior epigastric perforator (DIEP) flap to assess the perfusion of the skin island.[2] The use of intraoperative fluorescence angiography was validated as a reliable tool to assess flap perfusion and to lead the surgical decision making.[3] Therefore, in a consolidated trend of our surgical practice after elevating the flap and before ligating the vascular pedicle, we use the PDE to obtain a real-time information of DIEP flap perfusion and to identify the no-stained (not enhanced within 60 seconds) area that will be cut out.

Our standard to establish the sensor position on the flap refers to currently most updated criteria for free-flap NIRS monitoring as proposed by Akita et al.[4]

In our sample we always used the area enhanced within 10 seconds (early-stained area) for sensor location,[4] to obtain a standardization of the monitoring site.

The last question concerns the ischemia time and the underestimation of postoperative complications. As widely known, an increased rate in fat necrosis was observed in flaps with ischemia time exceeding 99.5 minutes.[5] Usually, we maintain a flap off–flap on time within 60 minutes. In our sample no flap had an ischemia time of more than 60 minutes and we did not report immediate vascular complications or late complication such as fat necrosis. Of course a reperfusion injury must be considered in the assessment of regional oxygen saturation (rSO2) values when the ischemia time is prolonged, but further studies should validate a more specific threshold value for this case.

• References

• 1 Salgarello M, Pagliara D, Rossi M, Visconti G, Barone-Adesi L. Postoperative monitoring of free DIEP flap in breast reconstruction with near-infrared spectroscopy: variables affecting the regional oxygen saturation. J Reconstr Microsurg 2018; 34 (06) 383-388
• 2 Holm C, Mayr M, Höfter E, Ninkovic M. Perfusion zones of the DIEP flap revisited: a clinical study. Plast Reconstr Surg 2006; 117 (01) 37-43
• 3 Pestana IA, Coan B, Erdmann D, Marcus J, Levin LS, Zenn MR. Early experience with fluorescent angiography in free-tissue transfer reconstruction. Plast Reconstr Surg 2009; 123 (04) 1239-1244
• 4 Akita S, Mitsukawa N, Tokumoto H. , et al. Regional oxygen saturation index: a novel criterion for free flap assessment using tissue oximetry. Plast Reconstr Surg 2016; 138 (03) 510e-518e
• 5 Lee KT, Lee JE, Nam SJ, Mun GH. Ischaemic time and fat necrosis in breast reconstruction with a free deep inferior epigastric perforator flap. J Plast Reconstr Aesthet Surg 2013; 66 (02) 174-181