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Page 2 of 17 Cevallos et al. Plast Aesthet Res 2023;10:30 https://dx.doi.org/10.20517/2347-9264.2023.01

INTRODUCTION
Microvascular free flap surgery represents an innovative reconstructive technique that has greatly
[1-3]
broadened the possibilities of surgical breast reconstruction . Recently, microsurgery has seen a surge in
popularity, accompanied by the introduction of new flap types and expanded indications for their use .
[4]
Nonetheless, the occurrence of flap loss remains a dreaded outcome, with reported failure rates ranging
[5-7]
from 2% to 5% . The considerable effort, time, and cost invested in microvascular breast reconstruction,
spanning from pre-operative planning to post-operative follow-up, intensify the impact of such losses. Pre-
operative planning, including possible imaging, may begin several months in advance. Post-operatively,
patients are admitted to the intensive care unit (ICU) for hourly flap checks during the first 48 hours, when
[8]
the flap is most vulnerable . However, evidence has emerged suggesting that patients can be safely managed
in step-down units instead of ICUs, allowing for accelerated discharges without an increased risk of flap
loss . Nevertheless, the costs associated with autologous breast reconstruction remain high. According to
[9]
the Healthcare Cost and Utilization Project National Inpatient Sample dataset, the average cost of a deep
inferior epigastric artery perforator (DIEP) flap for autologous breast reconstruction amounts to $22,677 .
[10]
Flap failure amplifies this already high cost by 50% to 77%, primarily due to extended hospital stays and the
need for secondary operations, thereby further compromising aesthetic and/or functional outcomes for
patients [11,12] .

Free flaps fail when tissue perfusion is compromised and unable to meet the metabolic demands of the
tissue. This occurs from inadequate inflow, inadequate outflow, or intrinsic issues. Among these causes,
venous insufficiency is the most frequently encountered, as veins are delicate structures prone to
compression or damage from trauma or pressure [13-15] . Certain intraoperative decisions can increase the
post-operative risk to the vasculature, such as the presence of perforators with long or tortuous courses.
Additionally, elevated tissue pressure, resulting from factors like edema, hematoma, or external
compression (e.g., positioning), can surpass perfusion pressure. Certain patient factors (e.g., age, disease,
body weight, smoking, pharmacological history), as well as the specific flap type, can further contribute to
[16]
the risk of experiencing any of these causes .

The initial 48-hour period following surgery poses the highest risk for flap failure, emphasizing the
importance of employing sensitive strategies for early detection. Timely identification of flap failure can be
instrumental in salvaging compromised flaps by prompting an urgent return to the operating room for
diagnostic assessment and salvage attempts [8,17-21] . Flaps can be successfully salvaged in 28% to 90% of cases,
but this range is highly dependent on the time of detection and take-back [22-25] . As the field of breast
reconstruction continues to expand with various options, the challenge of early detection has necessitated
the concurrent evolution of advanced flap monitoring techniques. For example, the introduction of nipple-
sparing mastectomy, which may involve immediate reconstruction using a buried free flap without a skin
paddle, requires the development of reliable monitoring methods independent of cutaneous visualization.
In addition to thorough clinical examinations conducted by experienced professionals, several adjunctive
post-operative monitoring technologies have been developed to complement physical examinations and
contribute to reducing failure rates. This narrative review summarizes the techniques employed to facilitate
early detection of threatened flaps in breast reconstruction, encompassing post-operative protocols, clinical
examinations, and supplemental technologies. We also highlight novel advancements and future directions
in plastic and reconstructive surgery.

POST-OPERATIVE FLAP MONITORING
Most institutions follow specific protocols to ensure standardized care during the vulnerable post-operative
period (48 h), typically in the ICU with trained staff and immediate access to the operating room if