An experimental investigation into the use of implanted thermocouples and differential thermometry as monitors for microvascular anastomoses.

It has been suggested that direct monitoring of arterial temperature using implanted thermocouples, may have value as a clinical postoperative monitor for vascularized free tissue transfers, including those with no visible surfaces. This study evaluated the technique in experimental animals, using simple, inexpensive equipment. Mean arterial differential temperature changes, with ipsilateral (n = 20) and contralateral (n = 21) references, of 0.6 degrees C and 0.5 degrees C respectively, reliably indicated occlusion of the superficial femoral artery in situ. In epigastric island flaps, arterial occlusion (n = 24) produced mean arterial temperature changes of 0.5 degrees C, but changes after venous occlusion were not significantly greater than unoccluded base line fluctuation. Venous differential temperature did not change significantly after either arterial or venous occlusion. In six epigastric free flaps, success or failure could not be distinguished, as the wide variation in measurements in the four successful flaps overlapped the recordings in the two which failed. It was shown that the nearer to the body core, the less the temperature difference between arterial wall and periarterial tissue. Occlusion of deeply sited arteries produced little or no change in arterial temperature. In view of these findings and because of the invasive nature of the technique, the authors did not pursue it clinically.