Cutaneous tissue flap viability following partial venous obstruction.

BACKGROUND: Venous outflow obstruction is the most common cause of tissue failure after microvascular reconstructive surgery. If it is not recognized early, there is an increased risk of tissue damage and loss. Currently, however, there are no adequate models for the study of this clinical problem. The purpose of this study was to develop a partial congestion model for the study of skin flap physiology in response to varying levels of occluded venous outflow.
METHODS: Nine mixed-breed pigs were equally divided into three experimental groups (0 percent, 20 percent, and 50 percent venous outflow) to determine the effects of varying venous outflow on cutaneous flap color, oxygen tension, and edema. A cutaneous pedicle flap model and a partial congestion system were used to observe changes in variable venous obstruction.
RESULTS: Only 0 percent venous outflow resulted in progressive color change across time. In addition, 0 percent venous outflow demonstrated significantly different oxygen tension levels relative to the other groups. Twenty percent venous outflow resulted in significant edema formation relative to the other groups. The 50 percent group showed an increase in oxygen tension from the second hour of venous obstruction to the end of the experiment.
CONCLUSIONS: Tissue flap color is the clinical standard on which flap health is measured. After 8 hours, only complete venous occlusion resulted in significant color change. However, physiological changes that could affect tissue flap health were noted with only partial venous occlusion, including the development of edema formation. Accordingly, subtle color change could indicate partial venous congestion and may warrant intervention by the surgeon.