The skin overlying the region where a venous "cut-down" is made to access the Great saphenous vein is supplied by:

The skin overlying the region where a cut down is made to grant access to the great saphenous vein is supplied by the saphenous nerve. The saphenous nerve is a branch of the femoral nerve. Ref: Textbook of Pediatric Emergency Procedures By Christopher King, Page 273; Clinical Anatomy By Regions By Richard S. Snell, Page 571