Implantable pulsed Doppler cuff for long-term monitoring of free flaps: a preliminary study.

High-frequency (20 mHz) ultra-sonic Doppler in a pulsed mode rather than continuous mode allows blood flow detection in small arteries using a 1-mm crystal embedded in a silastic cuff. The "probe factor" used to determine flow was first established in an in vitro system and found to be reliable. The probe was then tested in five dogs on the saphenous artery and found to be highly responsive to hemodynamic changes in the pedicle. Finally, in 15 long-term studies of island flaps and free flaps, the probes were implanted to obtain daily readings and then removed at 7 days. Except for some dog-related problems and technical errors, the system produced reliable flow data in the percutaneous cable. It is anticipated that such immediate and direct information on the pedicle blood flow would be useful in monitoring flaps.