Near infrared spectroscopy in monitoring of head and neck microvascular free flaps

Abstract

OBJECTIVES: Microvascular free-fl ap monitoring is crucial to the early detection of fl ap failure and increases the chance of early intervention in case of disruption of perfusion to a fl ap. Many clinical alternatives to classical clinical fl ap monitoring have been proposed, such as color duplex ultrasonography, handheld Doppler, fl ap thermometry, or implantable Doppler fl owmetry. Early detection of critical changes in tissue oxygenation can lead to successful surgical intervention when problems with fl ap nutrition arise. METHODS: Our clinical study seeks to investigate dynamic monitoring of free fl aps with near-infrared spectroscopy (NIRS). NIRS is a non-invasive instrumental technique used for continuous monitoring of peripheral tissue oxygenation (StO 2 ) and microcirculation. All patients were included prospectively from one clinical center. RESULTS: During the clinical research period, 18 patients underwent extraoral head and neck reconstruction with one of three types of free fl ap, namely with radial forearm free fl ap (RFFF), anterolateral thigh fl ap (ALT) or fi bula free fl ap (FFF). Measurements of fl ap perfusion were taken using NIRS during intraoperative and postoperative phases for 71 hours on average. A total of 6 perfusion disorders were recorded, of which three originated from microanastomoses and three from postoperative bleeding and compression of pedicle. NIRS showed characteristic changes in all 6 cases that were returned to the operating theatre owing to pedicle compromise. In these cases, NIRS had detected the pedicle compromise before it was clinically identifi ed. A single StO 2 monitoring was able to detect the vascular compromise with 100% sensitivity and 95.65% specifi city. None of the cases were falsely positive. In our study, all compromised fl aps were accurately identifi ed by means of NIRS. In most cases, the changes in oxygen saturation became evident on NIRS prior to being clinically observed. CONCLUSION: In our study, the continuous NIRS monitoring securely detected the early stages of arterial and venous thromboses or pedicle compression. The most important aspects of monitoring the fl aps´ microvascular perfusion and vitality by means of NIRS lie in its function of recording the dynamics of changes in the values of absolute oxygen saturation (StO 2 > 50%) alongside with detecting a 30% decrease in tissue saturation over a 60-minute interval (60 min StO 2 >30%) before the clinical changes in the microvascular fl ap become observable. In cases of pedicle compression, the average time of appearance of signs of StO 2 values dropping below the reference interval (as detected by NIRS) was 1:29:02 hour (SD= 0:58:42 h) prior to the occurrence of any clinical signs, while in cases of microvascular anastomosis complications, it was