Noninvasive monitoring of tissue viability.

Noninvasive monitoring techniques are procedures of little or no morbidity that may be repeated frequently to assess tissue viability. The ideal noninvasive technique would be safe, sensitive, reliable, reproducible, simple to use, and inexpensive. Although no such ideal technique yet exists, several currently available methods have clinical usefulness. Visual fluorescein, fluorescein photography, and surface fluorometry all work by the same principle. We prefer the surface fluorometer because of its greater sensitivity, the more objective nature of the data it provides, and the greater frequency with which it can be repeated. Ultrasound Doppler techniques are useful preoperatively in locating vessels and assessing their patency, and we have found the bidirectional Doppler quite helpful in the postoperative monitoring of replanted or revascularized digits. The laser Doppler, photoplethysmograph, and surface thermometer have not been as helpful in our experience. Transcutaneous oxygen measurement shows great promise for the postoperative monitoring of replants and free tissue transfers.