[Continuous free-flap monitoring with tissue-oxygen measurements: experiences of the last years].

Early recognition of flap failure is the prerequisite for flap salvage. Many methods are used to monitor free-flaps. The time interval for re-establishing vascular patency is the deciding factor for a successful revision. Prompt revision surgery and a quick and sufficient correction of the microvascular anastomosis are necessary to reestablish flap viability. The aim of this study was to evaluate the real impact of this probe as a continuous, precise and clinically relevant monitoring system in free-flap surgery. One of our main objectives was to create guidelines and "normal" ranges of p ti O 2 -values for the uncomplicated use of the Licox Probe in free-flap surgery for the first time. The Licox Catheter pO 2 Mikro-Probe instrument is used for continuous determination of oxygen partial pressure (pO 2 ) in body fluids and tissue (p ti O 2 ). Over a period of more than three years, 70 free tissue-transplantations to the head and neck, trunk, and upper and lower extremities were monitored by use of the implantable Licox Catheter Probe System. In all patients, a decrease of the p ti O 2 -levels was noted during the first minutes, until a more or less stable level was reached. At the time of weaning off, the p ti O 2 values decreased once again. After approximately 30 minutes, an almost stable but reduced p ti O 2 -level was reestablished (34,6 +/- 10,9 mm Hg). During the next days, we observed a more or less constant but reduced level. These values from the second day on were lower than the mean values of the first day. The mean value for all flaps was 23,1 +/- 6,5 mm Hg. Nevertheless, in all cases (10 of 70 flaps) where the p ti O 2 -level decreased more than 10 mm Hg within a half hour period, the flap showed vascular problems on re-exploration. Another clinically relevant value that was observed in all flaps with vascular problems was a drop of the p ti O 2 -value, below 10 mm Hg. In the cases of arterial thrombosis (2 of 10 flaps), a rapid decrease was noted. In the cases of venous complications (8 of 10 flaps), a more or less slow decrease of the p ti O 2 -value was observed. These observations may serve as precise indicators for vascular complications and flap failure. Based on our observations and data, it seems that the Licox-Probe is a sensitive and accurate monitoring system for a variety of free flaps.