Metabolism in myocutaneous flaps studied by in situ microdialysis

The aim of this investigation was to follow the metabolism of myocutaneous flaps using microdialysis. After subcutaneous implantation of a microdialysis catheter into the flap tissue, serial samples were collected and changes in composition of the extracellular fluid assessed. Ten women underwent reconstructions with transverse rectus abdominis myocutaneous (TRAM) or latissimus dorsi flaps. Glucose, glycerol, and lactate concentrations were measured in the flaps and compared with those in adipose control tissue located over the hip. A transient rise in glucose was observed initially in the flaps. The glycerol concentration also increased significantly, and remained increased for approximately 12 hours after the operation. The lactate concentration changed in the same direction, but stayed elevated in the flap tissue during the entire investigation (24 hours). Neither of these parameters changed to the same extent in the control tissue. In one of the patients a haematoma developed postoperatively in the flap. This incident was accompanied by a sharp decline in glucose, and marked additional increases in glycerol and lactate concentrations. It may well be that this "metabolic pattern" in flap tissue signals threatening flap ischaemia. If so, this new microdialysis technique may be useful as a postoperative surveillance tool in myocutaneous flap surgery.