Blood flow in free muscle flaps measured by color Doppler ultrasonography.

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.

Magnetization transfer imaging of the abdomen at 0.1 T: detection of hepatic neoplasms.

Magnetization transfer (MT) techniques have been proposed as a method of increasing contrast in MR images. To evaluate the feasibility of MT imaging of the abdomen at 0.1 T and to assess the clinical utility of this technique, the authors studied tissue contrast with a gradient-echo pulse sequence and an MT sequence in four normal volunteers, and in 17 patients with known primary or secondary neoplasms of the liver. The MT technique increased contrast between the liver and other tissues such as spleen, skeletal muscle and subcutaneous fat. The technique also produced increased contrast between hepatic tumors and normal liver parenchyma in gradient-echo images.

Prophylactic minitracheostomy after thoracotomy: a prospective, random control, clinical trial.

The effect of prophylactic minitracheostomy on the incidence of postoperative atelectasis and pulmonary gas exchange was evaluated in a prospective, random control study of 29 patients undergoing thoracotomy. Fourteen were randomly allocated to have a minitracheostomy, which was done in the recovery room immediately after operation, and the remainder acted as controls. Increased radiodensity and atelectasis were seen more often on the chest radiographs of the control patients on the first (p less than 0.05) and on the seventh postoperative days (p less than 0.01), irrespective of the extent of the pulmonary operation. Bronchial lavage under general anaesthesia or sedation was required by 6 of the 15 control patients, but by none of those who had had a minitracheostomy (p less than 0.05). These results support the hypothesis that minitracheostomy is a useful adjunct to postoperative care after thoracotomy.