POSTOPERATIVE BLOOD-FLOW MONITORING AFTER FREE-TISSUE TRANSFER BY MEANS OF THE HYDROGEN CLEARANCE TECHNIQUE

The hydrogen clearance technique was introduced for monitoring postope rative blood flow after free-tissue transfer in this prospective clini cal study. This technique allows unlimited repeatable quantitative mea surements of tissue blood flow in milliliters per minute per 100 gm of tissue at any site including buried flaps. In this study a real-time blood flow measuring system (Ameflow, Ameda, Switzerland) was employed . Two thousand eight hundred and twenty-three blood flow measurements were carried out on 72 free-tissue transfers, which were performed on 71 patients. Nine of these 72 flaps showed vascular complications (12. 5 percent), including arterial thrombosis in 6.9 percent (n = 5), hema toma in 4.2 percent (n = 3), and venous thrombosis in 1.4 percent (n = 1). Complications as well as uneventful postoperative cases were moni tored correctly by the hydrogen clearance technique in all cases, reac hing sensitivity and specificity values of 1.0 for this technique in o ur study. Furthermore, all complications could be detected earlier by the hydrogen clearance technique than by clinical monitoring alone, wh ich allowed flap salvation in 7 of 9 cases and a resulting permanent f ailure rate of free-tissue transfer of 2.8 percent (n = 2). From our d ata we conclude that the hydrogen clearance technique is a promising t ool for postoperative blood flow monitoring after free-tissue transfer . For experimental pathophysiologic and pharmacologic studies of tissu e blood flow in flaps, further evaluation of our measuring device incl uding comparative studies with other established techniques is highly recommended.