CONTINUOUS TISSUE OXYGEN-TENSION MEASUREMENT AS A MONITOR OF FREE-FLAP VIABILITY

Early recognition of vascular compromise within microvascular free-tis sue transfers is essential if reexploration is to prove successful. Ti ssue oxygen tension is increasingly recognized to be a sensitive and r eliable index of tissue perfusion, and preliminary studies suggest tha t it may be of value in the assessment of free-flap viability. We desc ribe our investigation into the application of an implantable microcat heter oxygen sensor in the monitoring of free flaps used in head and n eck and extremity reconstruction. In a preliminary study using the rab bit model, we sought to evaluate the response of oxygen tension as an index of tissue perfusion in myocutaneous (n = 20) and osteomyocutaneo us flaps (n = 5) under conditions of arterial and venous occlusion. A clinical study was then undertaken to evaluate the role of this method in the monitoring of surface and buried free flaps. In 30 heterogeneo us free-tissue transfers, sensors placed intraoperatively were used to provide continuous information about flap oxygen tension (mean monito ring period 3.2 +/- 0.8 days). The data generated were correlated with changes in clinical parameters and routine flap observations. Results for experimental and clinical data have confirmed the efficacy of con tinuous tissue oxygen measurements using this device as a method that provides an objective, recordable index of free-tissue transfer viabil ity in a variety of circumstances and vascular events. Tissue oxygen t ension is a suitable index by which to evaluate flap viability with th e probe placed in muscle or bone but is unreliable when used for the m onitoring of revascularized cutaneous flaps.