Some free flaps develop postoperative vessel thrombosis, which influences the flap survival rate. Early discovery and identification of vascular crisis are critical to the success rate of flap salvage. The primary aims of this study were to determine the features of postoperative blood supply changes in fibular flaps with normal and abnormal blood flow, using near-infrared spectroscopy (NIRS), to monitor oxygenation and blood flow, and to characterize the probable risk factors for vascular crisis.
Sixty-three consecutive patients undergoing reconstruction of unilateral mandibular defects with free fibular flaps at the Peking University School of Stomatology were included. Patients were divided into 2 groups, A (n = 38) and B (n = 25); fibular flaps in group A underwent continuous NIRS monitoring from immediately postoperatively until 7 days postoperatively (approximately 150 hours), whereas fibular flaps and opposite mandibles in group B underwent intermittent monitoring: once every 4 hours during the first 24 hours postoperatively and once every 12 hours from 24 to 168 hours postoperatively.
Six fibular flaps developed vascular thromboses: 4 were venous thromboses and 2 were arterial thromboses; 5 were rescued after exploration. Of 6 regional oxygen saturation (rSO2) values in the continuous monitoring group, 4 showed no significant differences at any time point compared with the intermittent monitoring group (P > 0.05). The rSO2 of the fibular flap was significantly different from that in the opposite mandible in the first 36 hours postoperatively (P < 0.05). This difference decreased over time. During the initial period of venous thrombosis, rSO2, deoxyhemoglobin, and oxygenated hemoglobin all rose slightly, then showed simultaneous rapid reduction. However, the magnitude of reduction was smaller for deoxyhemoglobin than for oxygenated hemoglobin.
Near-infrared spectroscopy can be used for noninvasive and reliable assessment of oxygenation and blood flow in free flaps through continuous, real-time monitoring. It is also portable, inexpensive, and simple to operate. In addition, the detection depth of NIRS is up to 2.0 cm, so it can be used to monitor buried flaps with depths <2.0 cm.