A Quick Evaluation of TRAM Flap Viability using Fingerstall-Type Tissue Oximetry

Abstract

Supplemental Digital Content is available in the text.

Zone IV, the most distal region of the transverse rectus abdominis musculocutaneous (TRAM) flap, is well known as a region of poor circulation.¹ We routinely use the indocyanine green (ICG) test, which has been widely used for decision-making regarding skin perfusion territory; however, the disadvantages of the test include the risk of an allergic reaction to ICG² and the need for an expensive imaging system. Tissue oximetry, a system measuring the tissue oxygen saturation (StO₂), has shown promise in postoperative flap monitoring.³ Recently, Kanayama and Niwayama⁴ developed a novel tissue oximetry technology, which allows the circulatory condition of the skin to be evaluated using a fingerstall-type StO₂ sensor. Then, the Toccare device (Astem, Japan) was released in 2015⁵. The advantages of this technology include the light weight of the module (0.1 kg), mobility (it works with batteries), and the short sampling time (0.5 s). We investigated the diagnostic potential of the Toccare device on the circulatory condition of TRAM flaps according to the distribution of StO₂ values and the results of ICG tests. The medical ethics committee of our institution approved this study. The investigation covered 2 reconstructive surgeries following breast cancer removal (Fig. 1).

Fig. 1.

A Toccare device showing the StO₂ value on its display. The module is light (0.1 kg) and runs on batteries. The sampling time is very short (0.5 s).

CASE 1

ICG test was performed and the outline of the fluorescence-negative region was marked (see figure, Supplemental Digital Content 1, which displays a right TRAM flap for breast reconstruction, http://links.lww.com/PRSGO/A534). Then, StO₂ values were measured at multiple sites on the skin surface of the flap, which were regularly placed at 2-cm intervals. During the measurement, a blue sheet was positioned under the flap so as not to catch any signals from the tissues beneath the flap. We also measured the StO₂ values of the upper abdominal region and excised skin as positive and negative controls, respectively. For each of the 3 longitudinal sites, the StO₂ values were averaged and recorded with a letter and a numeral, according to the side of the body and the distance from the ICG border (e.g., “L3” indicates the site located 3 cm from the border on the left). Sites of decreased StO₂ values located at R1-L1, which corresponded to the location of the outline of the ICG-negative region. Accordingly, the part lateral to the site was excised. The surgery resulted in no flap failure.

CASE 2

The tests were performed in the reverse order (Fig. 2). The boundaries with StO₂ values of 45% and 50% were determined first, and then the ICG test was performed. This determination took less than 5 minutes. The fluorescence-negative region corresponded to the region lateral to the 45% border. The estimated mean StO₂ value on the boundary between the ICG-positive and negative regions was 41.3%. We excised the skin at the ICG boundary; however, blood congestion was found. We therefore further excised the skin to the 45% region. Consequently, we confirmed the absence of blood congestion and flap failure.

Fig. 2.

Case 2: A right TRAM flap for breast reconstruction. The boundaries of the ICG border, StO₂ 45% and 50% are marked on the flap. The StO₂ values significantly decreased from 2 cm on the right side (R2) of the ICG border (n = 3). **p < 0.01 on a t test.

Although the methods by which oximetry systems are used require further investigation, we are of the opinion that the Toccare device has the potential to be an alternative to the ICG test.

Supplementary Material

gox-5-e1494-s001.pdf ^{(13.2MB, pdf)}