We used color Doppler ultrasound (US) to study postoperative changes in blood flow in 10 non-innervated free latissimus dorsi (LD) muscle flaps transplanted onto lower extremities. The peak, mean, and minimum velocities, resistance index, and diameter of the pedicle, and the recipient and control arteries were recorded preoperatively and on the 2nd, 5th, and 10th days after surgery. In the pedicle of the transplant, the peak and mean velocities increased but not significantly during the follow-up. The minimum velocity value in the thoraco-dorsal artery was (mean ± SD) 4 ± 5 cm/sec preoperatively, and was in the leg 19 ± 9 cm/sec (P < 0.05) on the 5th and 17 ± 10 cm/sec (P < 0.05) on the 10th postoperative day. The preoperative value of the resistance index decreased from 0.92 ± 0.12 to 0.79 ± 0.08 on the 10th postoperative day (P < 0.05). In the recipient artery, the peak (117 ± 37) and mean (35 ± 16 cm/sec) velocities increased significantly on the 5th postoperative day compared to the preoperative value (79 ± 22 and 14 ± 6 cm/sec, respectively). The minimum velocity increased but not significantly. The resistance index was preoperatively 1.23 ± 0.09 and 0.88 ± 0.16 (P < 0.05) on the 10th postoperative day. This prospective clinical study demonstrates that blood flow in the pedicle and in the recipient artery of a free muscle flap increases after surgery. This phenomenon may be due to loss of vascular tone and decreased resistance after denervation. Increased blood flow helps to keep the microanastomosis open and also promotes wound healing.© 1999 Wiley-Liss, Inc. MICROSURGERY 19:196-199 1999Color Doppler ultrasound (US) is a non-invasive technique providing information on the hemodynamics of blood flow. It can be used to measure vessel patency, the direction and velocity of blood flow, and the resistance index and diameter of vessels. 1-3 The technique can accurately distinguish veins from arteries and detect different vascular pathologies. 4 In free flap surgery, 5 Doppler ultrasonography has been used to follow blood flow in a LD free muscle flap, to detect vessels, 6 and to measure blood velocities after free flap surgery. 7 It has also been used to localize perforators in transverse rectus abdominis musculocutaneous (TRAM) flaps, 8,9 to precisely localize the pedicle of musculocutaneous gluteus maximus flaps, 8 and to monitor the patency of microanastomoses in a microvascular fibula flap. 10In our previous studies 6,7 we used this technique to study vessel patency and blood flow in free muscle flaps operated on 3-5 years earlier. We showed then that flaps with a patent pedicle have more muscle bulk and that bulky flaps on lower extremities are probably due to persistent, vigorous blood flow in the pedicle. 6 Our prospective study showed that blood flow in muscle flaps increases from the 2nd week to the 3rd month after the operation. 7It has been documented that blood flow increases in muscles immediately after denervation, 11 leading to arteriolar vasodilation with increased capillary perfusion. [11][12][13...
Color Doppler ultrasonography, a noninvasive method for studying changes in blood flow, has been used to monitor 18 patients with free microvascular lower limb muscle flaps. The peak, mean, and minimum velocities, resistance indices, and diameters of the flap pedicle arteries and also of the limb recipient arteries proximal to the microvascular anastomoses were measured at 2 and 6 weeks and 3, 6, and 9 months after surgery. The peak velocities did not significantly differ from each other, but the mean velocity in the flap pedicle arteries was 12.5% higher than that in the recipient arteries throughout the study period. End diastolic velocity in the pedicle was positive (toward the ultrasound probe) at 2 weeks (mean, 2 cm/sec, SD 10), 6 weeks (mean, 5 cm/sec, SD 16), and 3 months (mean, 3 cm/sec, SD 13) after surgery and significantly higher (P < 0.05) than at 6 months (mean, 7 cm/sec, SD 11), when the pattern of blood flow was normal forward/backward flow during systole/diastole. The resistance indices of the pedicle at 2 weeks (Ri = 0.978), 6 weeks (Ri = 0.936), and 3 months (Ri = 1.001) were significantly lower (P < 0.05) than at 6 months (Ri = 1.108), when the pedicle and recipient artery indices were the same. The diameter of the pedicle arteries was 14% smaller than those of the recipient arteries, but did not change during follow-up. This prospective clinical study shows that blood flow in the pedicle of a free microvascular muscle flap is increased until 6 months after surgery, mainly due to the increased minimum velocity of the pedicle in diastole and decreased resistance index. These findings can be attributed to the loss of vessel tone after denervation and are in accordance with earlier studies showing that denervated muscles lose their autoregulation and that blood flow increases, but that these phenomena subside with time. Increased blood flow in free muscle flaps can explain the high success rate of microanastomoses and positive effect on wound healing.
The skin islands of musculocutaneous flaps are nourished by perforating arteries. An easy method for accurately locating these vessels preoperatively would be valuable in flap design. Thermography is being developed in our center as a tool to locate the perforating vessels, which appear as ªhot spotsº on thermographic images. The abdominal perforators of 16 women were mapped out after warming or cooling the skin with COLDI-micro thermocushions. In group I (n=8) the thermo packs were applied to the lower abdominal skin for 30 s and in group II (n=8) for 300 s. In both groups all hot spots disappeared after warming. After cooling, the hot spots were clearer and more readily visible than at room temperature. The longer cooling time (300 s) gave a 3.4 times better contrast (p=0.03) than the shorter cooling time (30 s). The longer the cooling time, the longer the hot spots were visible. This work shows that cutaneous perforators can be sharply mapped preoperatively using thermography after simple bed-side cooling.
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