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In microvascular tissue transfers, it is essential postoperatively to follow-up on the perfusion of the transferred flap because of the risk of anastomotic failure. The diagnosis of pedicle obstruction is usually made by clinical observation, but some techniques have been reported as more reliable than clinical observation in detecting perfusion failure. The authors used microdialysis (MD), a method developed to assess in situ tissue metabolism, in the follow-up of 80 consecutive microvascular flaps from October, 2001 to October, 2003. Of the 78 flaps with postoperative data, 58 flaps were uneventful clinically and using MD, and served as the reference material for normal postoperative metabolism. Twenty flaps showed some abnormality in the clinical course or with MD. Of these, 13 flaps were reoperated for anastomosis thrombosis (9 arterial, 4 venous). All thromboses were clearly recognized by MD via a decrease in the glucose concentration in the tissue (< 2.7 mmol/l) and an increase in the lactate concentrations (> 5.7 mmol/l). In some cases, MD indicated a pathological trend in glucose and lactate concentrations hours before there were any clinical signs. A system of alarm levels was developed for the staff: when the limits were reached, a critical evaluation of the situation was undertaken, and the need for reoperation was considered. In the series, the salvage rate of all thrombosed flaps was 77 percent, with a final success rate in microvascular reconstruction of 95 percent. No flap was lost due to a delay in the diagnosis of secondary ischemia, if on-line MD monitoring was available. Microdialysis is a clinically feasible and sensitive monitoring method for all kinds of microvascular flaps, especially for those in which clinical observation is difficult or impossible. The performance of the analysis is easy and can be done by even less experienced nursing staff working in institutes with a low frequency of microsurgery.

Early diagnosis of postoperative perfusion failure is essential in microsurgical tissue transfer. In order to determine if microdialysis could be used in diagnosing flap ischemia, we tested this method in an experimental pig model. Sixty-six flaps (34 myocutaneous and 29 cutaneous) were created in 18 anesthetized pigs. During the experiment, secondary ischemia was induced for 5 h by selective clamping of the artery (20 flaps) or vein (21 flaps). Glucose, lactate, and pyruvate concentrations were measured hourly from the muscular and dermal layers. We found that decreasing glucose levels and increasing lactate concentrations were associated with arterial and venous occlusions from the first hour of ischemia. In venous ischemia, lactate concentrations remained lower than those in arterial ischemia. The increase in lactate-to-pyruvate and lactate-to-glucose ratios was related to ischemia and also discriminated arterial occlusion from venous occlusion. In conclusion, microdialysis can be used to facilitate early detection of ischemia.

Potentially, fibrin sealant combined with fibrinolysis inhibitor might be used for the treatment of post- axillary evacuation lymphorrhea and seroma.

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The purpose of this study was to investigate the common belief that a microvascular transfer of a non-innervated free muscle flap loses muscle bulk over time. Sixteen patients (latissimus dorsi = 8, rectus abdominis = 7, and gracilis muscle = 1) were evaluated an average of 41 months after free flap transfer. Latissimus dorsi and lower extremity flaps displayed significantly more swelling than the other flaps. Flap bulk was measured by ultrasound. The mean thickness of upper extremity flaps was 10.3 +/- 1.8 mm (control muscles 11.8 +/- 2.8), lower-extremity 14.5 +/- 3.7 mm (control muscles 10.9 +/- 0.7), latissimus dorsi 14.3 +/- 2.2 mm (control muscles 10.3 +/- 0.8, P = 0.018), and rectus abdominis 11.2 +/- 1.2 mm (control muscles 12.4 +/- 1.9). Color Doppler ultrasonography was used to detect the pedicles of the free flaps and also to measure the peak velocity of blood flow intramuscularly and in the pedicles. In the upper extremities (n = 5) the pedicles could be found in only 20% of cases whereas in the lower extremities (n = 11) 91% of pedicles were located. (P = 0.013). Peak flow within the free flaps was significantly higher in the lower extremity (50% of the peak flow of the common femoral artery) than in the upper extremity (5% of the peak flow of the common femoral artery, P = 0.013). This study demonstrated that non-innervated free muscle flaps in the extremities maintain the original muscle thickness, although lower extremity and latissimus dorsi flaps have a trend to be thicker. Most pedicles of free muscle flaps in the upper extremities could not be located by ultrasound. However, flaps in the lower extremities most often have patent pedicles and also more vigorous intramuscular blood flow.

To investigate tissue metabolism during suboptimal blood perfusion, we used in situ microdialysis in an experimental model of myocutaneous flaps. We assessed concentrations of glucose, lactate, and pyruvate in flaps subjected to partial pedicle obstruction and to hemorrhagic shock. When the arterial flow was restricted, the glucose concentration decreased in the flap muscle, and the lactate concentration increased in all flap components. The restriction ofvenous outflow resulted in lactate overproduction and a decrease of glucose in skin and muscle. The lactate-to-pyruvate ratio remained normal during arterial obstruction but increased during venous obstruction. During hypovolemic shock, the lactate production increased and the glucose concentration decreased or remained normal. The metabolic changes occurring during partial pedicle obstruction and hypovolemic shock are moderate and different from those seen in total pedicle obstruction. Microdialysis is a feasible method for assessing local tissue metabolism and can be used to monitor flap ischemia.