as shown in fig3 referring to fig3 a a portion of the vascular anatomy of an arm which may be an alternative utilized anastomosis site as illustrated wherein instead of joining the ima to the lad in a bypass procedure an a v fistula is performed utilizing surgical instrument 100 to join the radial artery end to side with the cephalic vein sometimes called the radial vein other a v fistulas which may also be achieved utilizing surgical instrument 100 include joining the ulnar artery end to side with the basilic vein sometimes called the ulnar vein such a v fistulas are performed to facilitate hemodialysis for end stage kidney disease to allow a single puncture at the dialysis unit for blood cleansing the fistula allows a greater flow tate through the dialyzer not shown referring to fig3 39 an alternative embodiment of the firing safety mechanism illustrated in fig2 24 is illustrated which also prevents the unintended firing of surgical instrument 100 the firing safety mechanism includes a lock spring 350 and a safety release slide 360 referring to fig3 and 33a safety release slide 360 includes a pair of camming surfaces 360 a and 360 b which interact with cam follower surfaces 350 d and 350 e lock spring 350 as best illustrated in fig3 includes a body portion 350 a that defines a yoke a pair a leaf spring portions 350 b and 350 c and a pair of cam follower surfaces 350 d and.