Distinguishing laser Doppler flowmetric responses between arterial and venous obstructions in flaps

This study emphasizes the differences in laser Doppler flowmetric responses between arterial and venous obstruction of flaps, by using an experimental model and a clinical review. Monitoring free flaps in the early postoperative period is valuable in the salvage of failing flaps. When combined with clinical observation, the laser Doppler flowmeter can provide the surgeon with an early indication of impending flap failure, which enhances the success rate of flap salvage. Understanding the difference in laser Doppler flowmetric response between venous and arterial occlusion allows for improved interpretation of the perfusion data. The authors monitored 12 epigastric skin island flaps in six male Sprague-Dawley rats, comparing flow data between venous and arterial occlusion. Arterial occlusion consistently led to an abrupt fall below the critical value within 1 min, while venous occlusion consistently showed a more gradual decline over 15 min and beyond. In the authors' clinical series of 13 failing flaps recorded by the laser Doppler, three cases of arterial occlusion showed an abrupt decline in flow values, while 10 cases of venous obstruction showed a gradual decline to critical value, usually over several hours. When monitoring free flaps using the laser Doppler, it is crucial to pay special attention to any gradual decline in flow values, in order to detect impending flap failure and to expedite reexploration.