A review of devices used in the monitoring of microvascular free tissue transfers

Abstract

The use of microvascular anastomoses to allow transfer of viable tissue is a fundamental technique of reconstructive surgery, and is used to treat a broad spectrum of clinical problems. The primary threat to this type of reconstructive surgery is anastomotic vascular thrombosis, which can lead to complete loss of tissue with potentially devastating consequences. Monitoring of tissue perfusion postoperatively is critical, since early recognition of vascular compromise and prompt surgical intervention is correlated with the ability for tissue salvage. Traditionally, physical examination was the primary means of monitoring, but possesses several limitations. Medical devices introduced for the purposes of flap monitoring address many of these deficiencies, and have greatly enhanced this critical aspect of the reconstructive surgery process.

Keywords::

• free flap
• flap monitoring
• free tissue transfer
• microvascular reconstruction

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• • In reconstructive surgery, the use of microvascular anastomoses to transfer tissue from one anatomic site to another is a fundamental technique. This type of surgery (free flap surgery) is used to treat a broad spectrum of clinical problems, including injuries sustained from cancer, infection, trauma and congenital defects.

• • Thrombosis of microvascular anastomoses results in loss of tissue, which can have devastating consequences. Early detection of vascular compromise is critical, since expeditious surgical intervention is correlated with the ability for tissue salvage.

• • Physical examination is the cornerstone of free flap monitoring, but medical devices serve as a valuable complement by providing in many cases accurate, continuous, instantaneous, reproducible and sensitive information about perfusion.

• • Acoustic Doppler sonography is a reliable method that is simple to use, and will likely remain an essential adjunct to physical examination.

• • Color duplex ultrasonography (CDU) utilizes equipment available in most hospitals to directly visualize flow across microvascular anastomoses. Its use is greatly limited by the need for a technician, radiologist and microvascular surgeon to perform and interpret the evaluation.

• • The implantable Doppler is an invasive technique that monitors flow immediately adjacent to microvascular anastomoses. It is particularly useful in tissue transfers that lack an external component where use of other monitoring modalities is precluded.

• • The flow coupler combines a commonly used anastomotic technique for venous anastomoses with a micro-Doppler probe to monitor flow. Current models demonstrate a tendency for signal inconsistency, premature probe removal and unwanted forces on anastomoses, which limits its use.

• • Laser Doppler flowmetry is a non-invasive method that provides continuous measurements of blood velocity using laser light. Clinical studies support its use in free flap monitoring. Further study is necessary to establish criteria for diagnosing vascular compromise.

• • Spectroscopic methods of flap monitoring utilize near-infrared or visible light to measure oxygen saturation and hemoglobin concentration. Current device models are non-invasive and provide continuous measurements, with demonstrated clinical efficacy.

• • Newer devices are likely to combine existing technologies into a single device that delivers multiple measurements in real-time to mobile devices.

• • Further investigation is necessary to determine whether the benefits of flap monitoring devices justify the associated financial costs.

Notes