REGIONAL VARIATIONS OF LASER DOPPLER BLOOD-FLOW IN ISCHEMIC SKIN FLAPS

An island skin flap was designed on the left inferior epigastric neurovascular bundle of anesthetized male rats. Blood flow was measured in situ with a laser Doppler flowmeter at 20 discrete points on a grid system (5 points in each quadrant of the flap) before and after surgery, or before vascular occlusion, during reperfusion, and 48 to 72 hours later. Two series of experiments were performed. In the first series, the raised flap was placed in a bath containing heated Ringer’s solution and the left pedicle was cross-clamped. After 30 minutes, adenosine at a concentration that produced supramaximal vasodilatation, or its vehicle, was added to the bath. After 1 hour total occlusion time, the vascular clamp was released and adenosine treatment was continued for the first 30 minutes of reperfusion. In the second series, the protocol was similar except that adenosine, or its vehicle, was infused into the ischemic flap by means of the distal stump of the right inferior epigastric artery. After 48 to 72 hours, fluorescein was injected IV. The data showed a significant regional variation in baseline laser Doppler blood flow that was further altered by surgically raising the flap. Whereas proximal axial laser Doppler blood flow was essentially unchanged from the preoperative baseline, distal axial laser Doppler blood flow decreased 10 to 50 percent, and proximal and distal dependent laser Doppler blood flow decreased 50 to 80 percent. Thus no single value accurately reflected total flap perfusion. Necrosis occurred only in the dependent flap regions, which confirmed previous work. In the dependent regions, especially along the incision line, postoperative laser Doppler blood flow was lowest. Fluorescein penetration at 48 to 72 hours was strongly correlated with laser Doppler blood flow if a correction factor of 2.3 was considered. With adenosine treatment, in contrast to its vehicle, laser Doppler blood flow tended to increase during the postoperative period. We conclude (1) that surgical construction of a skin flap can aggravate a regional variation in perfusion that can be detected with a laser Doppler flowmeter, (2) that continuous monitoring of laser Doppler blood flow at a single site could be misleading unless tissue perfusion is uniform, and (3) that adenosine has a potential beneficial effect in ischemic skin tissue. © 1990 American Society of Plastic Surgeons.