Monitoring partial and full venous outflow compromise in a rabbit skin flap model.
BACKGROUND
Free flap failure often results from venous thrombosis. The authors developed a rabbit flap model of partial venous obstruction and evaluated four monitoring devices in detecting partial and full venous compromise.


METHODS
Nine skin flaps were elevated on their arteriovenous pedicles in rabbits. The flap was assessed with quantitative Doppler of arterial inflow, transcutaneous oxygen and carbon dioxide tension, near-infrared spectroscopy tissue oxygen saturation, and scanning laser Doppler imaging. After a stable baseline was achieved, the outflow vein was subjected to partial and full venous obstruction followed by release.


RESULTS
Pedicle arterial flow decreased significantly from baseline (5.9 +/- 3.0 ml/minute) during partial (4.1 +/- 2.4 ml/minute; 30.5 percent; p < 0.01) and full obstruction (0.3 +/- 0.4 ml/minute; 94.9 percent; p < 0.01). All other measures changed significantly with full obstruction: transcutaneous oxygen tension decreased by 79.6 percent; transcutaneous carbon dioxide tension increased by 69.0 percent; near-infrared spectroscopy tissue oxygen saturation decreased by 35.7 percent; and scanning laser Doppler imaging decreased by 78.8 percent. Laser Doppler imaging was the only noninvasive device that decreased significantly (p < 0.01) with partial obstruction, from 222.8 +/- 77.3 units to 186.5 +/- 73.2 units (16.3 percent).


CONCLUSIONS
The authors established a venous obstruction flap model and evaluated four clinically relevant monitoring devices during partial and full venous occlusion. All devices detected full occlusion, but only scanning laser Doppler imaging and arterial Doppler detected partial occlusion. Scanning laser Doppler imaging monitoring may allow warning of impending venous obstruction. Near-infrared spectroscopy tissue oxygen saturation varied the least between flaps and therefore may be the most easily interpreted device for full venous occlusion. Both characteristics are important for clinical application.
Gimbel
Michael L
ML
Pittsburgh, Pa.; San Francisco, Calif.; Tokyo, Japan; and Salt Lake City, Utah From the University of Pittsburgh; the University of California, San Francisco; Tokyo Women's Medical University; and the University of Utah.
Rollins
Mark D
MD
Fukaya
Eri
E
Hopf
Harriet W
HW
D000818:Animals; D001783:Blood Flow Velocity; D001785:Blood Gas Monitoring, Transcutaneous; D017078:Laser-Doppler Flowmetry; D010100:Oxygen / Q000378:metabolism; D011817:Rabbits; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply* / Q000378:metabolism; D019265:Spectroscopy, Near-Infrared; D013524:Surgical Flaps / Q000098:blood supply*; D014690:Venous Pressure; D020246:Venous Thrombosis / Q000503:physiopathology
D010100:Oxygen