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Inchauste. Plast Aesthet Res 2023;10:27 https://dx.doi.org/10.20517/2347-9264.2022.139 Page 3 of 15

breast reconstruction relies on the patency of very small vessels to be successful. Extreme care must be taken
during vessel dissection to minimize tension on vessels and avoid avulsion or intimal injury. The same care
is required during the preparation and handling of vessels during microvascular anastomosis.

Endothelium is the inner cellular lining of all vessels and constitutes the intima layer. The endothelium
controls vascular relaxation and constriction . Injury to the endothelium can result in vasospasm or
[15]
constriction as well as platelet adherence and clot formation. Studies have shown that damage to the intima
increases the risk of thrombus and flap loss . It is important to minimize instrumentation to both the
[16]
recipient and flap vessels, especially within the lumen of the vessel. The lumen of the vessels should be
visualized under high magnification and carefully inspected for any tears or separation of the intima. This is
especially critical when the patient has a history of radiation. Radiated vessels are more friable and prone to
intimal injury. Prior radiation therapy is not a contraindication but awareness of the potential damage to
recipient vessels is needed. Compared to implant-based reconstruction and immediate autologous free flap
breast reconstruction in postmastectomy radiation patients, delayed autologous free flap breast
reconstruction is associated with higher patient satisfaction, fewer revision surgeries and lower long-term
[17]
complications . If an intimal injury is seen, the vessel needs to be trimmed back until healthy, uninjured
intima prior to proceeding with the anastomosis. Further dissection of the vessels may be needed to achieve
appropriate exposure to healthy-appearing vasculature. In the setting of poor vessel quality, such as
radiation damage or atherosclerotic disease, the use of alternative vessels or vein grafts may be warranted, as
discussed below.

Once the vessel is trimmed back to a healthy lumen and appropriate length, the outside of the vessel is
prepared. The vessels are separated, and surrounding fatty tissue removed. The outer layer of connective
tissue surrounding a blood vessel is the tunica adventitia or tunica externa. Adventitia is comprised of
collagen, elastic fibers, and perivascular nerves. The adventitia plays an important role in controlling lumen
size through the regulation of the smooth muscle tone. Activation of sympathetic fibers within the
adventitia causes vasoconstriction and lumen narrowing. Interruption of these sympathetic fibers within the
adventitia leads to decreased activation of smooth muscle tone and vasodilation . Limited resection of the
[18]
adventitia around the artery during vessel preparation has been shown to reduce vascular tone and increase
[18]
lumen size, and vascular flow during microvascular anastomosis . Vasodilation and increased flow
improve anastomotic patency and decrease thrombosis. Care must be taken to not over-resect the adventitia
and weaken the vessel. Limited adventitiectomy around the circumference of the vessel edge with
microscissors can provide the desired sympathectomy without compromising the vessel integrity.

Magnification:

Visualization is crucial to performing a successful microvascular anastomosis. It is critical to see all the
structures of the vessel and suture placement. The use of surgical microscopes for appropriate visual
magnification to perform microvascular anastomoses remains the predominant method. The magnification
achievable with most operating microscopes is between 6× and 40×. More recent publications have shown
microsurgical anastomoses performed with loupes magnification to be safe and effective for free flap breast
[20]
reconstruction [10,19,20] . Loupes provided 3.5× to 5.5× magnification . Small vessel diameters equal to 1.5 mm
or less still require operative microscope magnification . One must consider that the authors of most
[20]
publications regarding loupes microsurgery are very experienced microsurgeons. Novice surgeons learning
microsurgery may not have equivalent outcomes. The operative microscope allows for significantly better
visualization with magnification twice to forty times as powerful as loupes. Newer operative microscopes
are equipped with integrated near-infrared illumination systems that can be used to evaluate intraoperative