BLOOD-FLOW VELOCITY AS A FACTOR IN POSTOPERATIVE MICROVASCULAR PATENCY

The authors attempted to develop a reliable and reproducible new anima l model in which the blood-flow velocity to a flap could be varied. Th is model was utilized to study the effects of different blood-flow vel ocities on the patency rate of small 1- to 2-mm vessels after common m icrosurgical procedures. Male Sprague-Dawley rats, weighing 450 to 550 gm, were used to develop a model creating either a ''high blood flow' ' or a ''low blood flow'' state by ligating the rat femoral artery, ei ther distally or proximally, to an epigastric artery based on a groin cutaneous flap. Blood-flow velocities were measured by microvascular f lowmeter, and statistical analysis was performed on the data collected . The model was next used to determine the effects of different blood- flow velocities on the patency rates of rat femoral vessels after prim ary anastomosis vs. interpositional vein grafting. Interpositional vei n grafting was subsequently repeated by a more senior microsurgeon, to determine the potential effects of increased surgical experience. The animal model was reliable, easily reproducible, and efficacious in pr oducing two separate groups of rats with significantly different blood -flow velocities (3.98 vs. 2.14+/-0.5 ml/min), as was confirmed by ele ctromagnetic flowmeter and statistical analysis. In experienced hands, decreased blood-flow velocity did not result in decreased patency rat es of these small vessels after primary anastomosis, or even after vei n grafting. As long as microvascular vein grafting and primary anastom osis procedures are done properly, even 1-mm vessels can tolerate sign ificantly decreased blood-flow velocity without a decreased patency ra te. Although many known factors can contribute to thrombosis and failu re of anastomoses in clinical microsurgery, blood-flow velocity appear s not to be a significant factor. Also described is a new, reliable an imal model that can be used in small-vessel blood-flow velocity studie s.