Advanced Optical Monitoring of Free Tissue Transfer Hemodynamics

PURPOSE: To improve the design and evaluation of a novel spatially resolved near-infrared spectroscopy (NIRS) system customized for continuous postoperative free tissue transfer (FTT) monitoring and to make this system commercially available.

HYPOTHESIS: The novel NIRS device is capable of monitoring FTT reconstruction continuously for 72 hours after surgery with minimal interference to patient care, minimal discomfort to the patient, and minimal interference with clinical assessment.

JUSTIFICATION FOR THE STUDY: FTT consists of transplanting skin, muscle or bone along with its feeding blood vessels from one body site to reconstruct a defect created by removing cancerous tumours or traumatic injury at a separate site. The key to the survival of the transplanted tissue is the meticulously created microvascular anastomosis between the blood vessels of the transplanted tissue and the blood vessels of the recipient site. Microsurgical techniques have been refined over time to maintain the patency of the anastomosed blood vessels. Nevertheless, the current FTT failure rate is between 1 and 10%.

When FTT failure occurs, it is a devastating experience for the patient and the surgical team. The patient has to be urgently brought to the operating room for an attempted salvage of the microvascular anastomosis. In the event of unsuccessful salvage, the patient has to undergo multiple surgeries that compound the associated morbidity, prolong hospital stay, and increase health care costs. Early detection of vascular compromise is essential for increasing the odds of successful salvage. Thus, the methods used to monitor the FTT vascular status are critical and have received much attention in the literature. Clinical examination remains the gold standard and the most popular method of monitoring FTT viability. The two downsides of clinical examinations are the requirement for personnel trained and experienced in FTT monitoring and the inability to provide reliable continuous monitoring. Therefore recognition of FTT compromise is often delayed significantly compromising successful surgical salvage attempts.

Recently, NIRS has been recognized as the technology with the most potential to address the problems seen with FTT clinical monitoring. NIRS is a non-invasive technique that passes near-infrared light (600-1000 nm) through the tissues at a depth of 10 to 20 mm. Calculating the amount of absorbed light allows real-time measurements of oxygenated, deoxygenated, and total hemoglobin concentrations. Therefore, an abnormality of tissue perfusion and oxygenation can then be detected instantaneously and confirmed clinically. Reducing the time from detection of vascular compromise to the attempted FTT rescue in the operating room decreases the ischemia time and increases the FTT salvage rate.