Effect of bipolar coagulation and occlusion clamping on the patency rate in microvascular anastomosis

Even with extremely high output from a bipolar coagulator applied close to a vessel, the patency in the femoral arteries and veins of 20 rats was found to be excellent. Scanning electron microscopy and histopathologic studies showed minimal disturbances within the intima. When the extremely high pressure (350 gramforce/mm2) of the Ikuta microvascular occlusion clamp was applied to the rat femoral veins for 1 hour, only one out of six veins became nonpatent. Lower pressures had no detrimental effects on the other 33 veins. When high clamping pressure and high output bipolar coagulation were applied together in 20 femoral veins of the rat, patency rate was 80 percent. From the results, it appears that bipolar coagulation is extremely safe, while clamping can be harmful to patency in microvascular anastomoses.     

Effect of torsion on microarterial anastomosis patency

All kinds of technical faults must be prevented in microvascular anastomosis for successful reconstructive microsurgery. Torsion at the anastomosis site is one of the most basic technical errors. In this study, we investigate the effect of different degrees of microarterial torsion on patency and its physical changes on anastomosis in a rat model. A total of 144 microanastomosis were performed in 72 Sprague-Dawley rats. They were divided into 9 groups. The anastomosis was performed at 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, 315 degrees, and 360 degrees of torsion randomly. Patency rates and the narrowest point of the artery after the anastomosis were recorded after 1 hour for each group. In the second stage of the study, the 9 groups were divided into 2 groups for patency rates and histopathological sampling at the second and seventh days postoperatively. The femoral arteries in all groups were all patent at the end of 1 hour. Only 5 microanastomosis were thrombosed (one in the 45 degrees group, one in the 225 degrees group, one in the 270 degrees group, and two in the 315 degrees group) at the second day of exploration. Only two arteries were thrombosed (one in the 45 degrees group and one in the 315 degrees group) at the seventh day of exploration. The patency rate was 96.8% in experimental groups excluding the control group. Different degrees of torsion had no statistically significant effect on the patency rates of microvascular anastomosis. Torsional repair of the femoral artery in the rat has no significant histopathologic changes, but alternately, endothelial integrity was affected by excessive degrees of torsion. Different degrees of torsion at the anastomosis site do not affect patency rates and cross sectional histology of rat femoral arteries. In clinical practice, minor torsion can be tolerated, however, factors affecting patency such as tension, diameter disproportion, and tight closure can affect the final result of anastomosis. We observed that torsional force of the vessel is distributed along the artery to the weakest point.     

Aortic arch occlusion technique using a balloon during open proximal anastomosis

We report a new aortic arch occlusion technique with a balloon for distal aortic arch repair via left thoracotomy using an open proximal method. Distal aortic arch repair via left thoracotomy sometimes causes brain infarction and perioperative myocardial infarction. That is because air or debris enters into coronary arteries and cervical branches and the left ventricle. Occlusion of the aortic arch using a balloon can prevent such perioperative complications.     

Effect of hyperbaric oxygen on microvascular anastomosis healing and patency in the rat

Recent evidence has shown that changes in blood viscosity and marked increases in both platelet count and fibrinogen concentration occur after exposure to hyperbaric oxygen (HBO). The purpose of the present study was to address whether repeated HBO therapy would increase either hematocrit or platelet count, and to determine if these changes would influence the patency of the microvascular anastomosis, as well as anastomotic healing. Eighty femoral arteries from 40 rats were divided into four groups (n = 10), and arterial anastomoses were performed on normal arteries in the first two groups, and on crushed arteries in the second two groups. One of the normal artery groups and one of the crushed artery groups received repeated HBO treatments for 5 days. Anastomotic patency rates, platelet count, hematocrit, and breaking strength were recorded. Among the results of this study were that: (1) there was no difference in patency rate following HBO treatment in both the normal and crushed artery groups; (2) platelet count was significantly higher following HBO treatment in the groups with the undamaged arteries; (3) breaking strength was significantly increased following HBO treatment in the groups with the crushed arteries. The authors concluded that HBO therapy may be useful in improving the healing of microvascular anastomoses in vessels that have undergone crush injury. Although HBO treatment results in an increased platelet count, this does not influence anastomotic patency.     

Effect of nicotine on blood flow and patency of experimental microvascular anastomosis

Nicotine is known to have deleterious effects on the cardiovascular system, causing vasoconstriction and increased blood pressure. A drop in blood-flow velocity in humans, endothelial damage in rats, and inhibition of platelet aggregation in rabbits' blood have all been shown experimentally. In this article two studies are described that investigate the effects of nicotine on microvascular anastomotic patency. In experiment 1, electromagnetic blood-flow recordings were made in the saphenous artery of the saphenous flap after intraarterial installation of nicotine. Decreased blood flow was consistently recorded up to a maximum of 72% of normal flow. In experiment 2, rabbit femoral arteries were anastomosed and the patency rates at three weeks checked after various combinations of pre- and postoperative intraperitoneal nicotine had been injected. There was no significant increase in thrombosis between the groups treated with nicotine and the control. Although no thrombosis occurred in these experiments, decreased blood flow was noted in the saphenous flap in the dog. This slowing of flow should predispose to thrombosis, especially if other factors associated with the vascular repair were suboptimal. It is concluded in view of this study and the observed clinical effects in 2 patients with microvascular transfer that smoking in the perioperative period should be avoided.     

Effect of anastomosis and geometry of vessel curvature on blood flow velocity and patency in microvessels

The effect of the geometry of the vessel and the number of anastomoses on the blood flow was studied. Four different shapes of the vessel were constructed by using a 6-cm-long double vein graft model with three anastomoses: (1) an alpha loop, (2) an omega loop, (3) a sigmoid curve, and (4) straight. Blood flow was measured by an ultrasound Doppler flowmeter. The result showed no alternation in blood flow across different geometry and through three patent microanastomoses. However, six out of seven vein grafts were thrombosed at 24 hr postoperative due to vascular kinks. This model demonstrates potential sites of kinking at the dissection end of the femoral artery, the microanastomoses, the side branches of the vein graft, and the adventitial adhesions. This model is recommended to microvascular trainees for the study of kinking and the management of redundant pedicles and vein grafting. © 1997 Wiley-Liss, Inc MICROSURGERY 17:491–494 1996     

Assessment of the patency of microvascular venous anastomosis

There is an absence of data on the timing of occlusion of vessels after anastomosis, and on the possible subsequent reopening (recanalization) of these vessels. This lack of information may be an important factor in the wide discrepancies found among reported patency rates for laboratory microvascular repair. In this study, a total of 300 standard microsurgical anastomoses were performed on rat femoral veins. The patency of each anastomosis was assessed at regular intervals within a 2-week study period. These results showed that the majority of venous occlusions occurred within 1 day after repair. Recanalization of the occluded vein was first seen at day 3 postoperatively. Recanalization was observed over a 2-week postoperative period with increasing frequency. The authors conclude that the optimal time to assess the technical outcome of experimental venous patency is 1 to 2 days after the repair.     

The effect of nifedipine on the patency of microvascular anastomosis in rats

Despite advances in microsurgical technique and experience in clinical microvascular surgery, there remains the possibility of vessel thrombosis. Factors that may contribute to vascular pedicle thrombosis include operative trauma, pedicle malposition, kinking, hypercoagulability and arterial vasoconstriction. The purpose of this study was to evaluate the effect of intravenous administration of nifedipine on the patency of the microvascular anastomosis of the femoral artery in rats. A total of 60 rats were used and divided into three groups. The first group (A) was used as a control group with no medical agent, the second group (B) was medicated with heparin, and the third group (C) was medicated with nifedipine. Patency was assessed with the distal empty refill test, one hour (1) and forty-eight hours (48) after completion of the anastomosis. The nifedipine and heparin treated groups (B & C) did not show higher patency rate compared to the control group (A). There was no statistically significant difference of patency percent after 1 hour and 48 hours among the three groups (p = 0.231/p = 0.480). Intravenous administration of nifedipine does not improve the patency of microvascular anastomosis. Surgical technique remains the most important factor for successful microvascular anastomosis.     

End-to-end versus end-to-side arterial anastomosis patency in microvascular surgery

The patency rates of microsurgical end-to-end and end-to-side anastomosis in the rat carotid artery were studied. Seventy end-to-end and seventy end-to-side arterial anastomoses, using 10-0 nylon interrupted sutures, were performed on 140 Sprague-Dawley rats. Findings indicated 100% patency in end-to-end as well as end-to-side immediately and 1 week post-anastomosis. This investigation suggests that there is no significant advantage between the methods studied based on vessel patency alone. The decision to perform an end-to-end vs. an end-to-side arterial anastomosis should be based upon the clinical circumstances encountered, since no significant difference in patency rates exists. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:125-128 1998     

Effect of a selective thromboxane synthase inhibitor on arterial graft patency and platelet deposition in dogs

This study examined the effect of selective thromboxane synthase inhibition and nonselective cyclooxygenase inhibition on vascular graft patency and indium 111-labeled platelet deposition in 35 mongrel dogs undergoing carotid artery replacement with 4 mm X 4 cm polytetrafluoroethylene (PTFE) (one side) and Dacron (opposite side) end-to-end grafts. Aspirin-dipyridamole therapy improved one-week graft patency, from 46% in untreated dogs to 93% in treated dogs. Thromboxane synthase inhibition (U-63557A) improved graft patency in these dogs to 81%. Both drug treatments reduced platelet deposition on Dacron and PTFE grafts by 48% to 68% compared with control dogs. Dacron grafts accumulated significantly more platelets than PTFE grafts but had comparable patency rates. Low-dose aspirin therapy had no significant effect on either graft patency or platelet deposition. All treatment groups showed a 60% to 76% reduction in serum thromboxane B2, but only thromboxane synthase inhibitor treatment increased plasma 6-keto-prostaglandin F1 alpha by 100%. Selective thromboxane synthase inhibition improved small-caliber prosthetic graft patency to the same extent as did conventional cyclooxygenase inhibition in this preliminary study.     

Effect of the two-wall-stitch mistake upon patency of rat femoral vein anastomosis: Preliminary observations

Anastomotic patency is believed to be the most important factor in microvascular surgery. The two-wall stitch is a technical error commonly considered to cause thrombosis of the anastomosis, especially on the venous side. In order to demonstrate the real effect on vein patency of the two-wall stitch, the authors performed a standardized mistake after correct microanastomosis on the femoral vein of 15 rats, with one stitch passing through the whole thickness of the two walls of the vein. Traditional correct anastomoses on the contralateral side were used as controls. Patency was assessed at 5, 20, and 60 min and at 24 h by the milking test, and by direct section of the vessel at 24 h. The results showed no statistically significant difference between the two techniques. Histological examination confirmed the clinical judgment about the vessel's patency, and ultrastructural microscopy evidenced only mild signs of endothelial activation. In conclusion, this study indicates that the occasional two-wall stitch does not necessarily increase the risk of venous occlusion in anastomoses of the rat femoral vein.     

Free right internal thoracic artery as a second arterial conduit: modification of proximal anastomosis for improvement of graft patency.

The applicability of the right internal thoracic artery (RITA) for coronary artery bypass grafting is higher when used as a free graft than as a pedicled graft. However, the technical difficulty of directly connecting the proximal end of the free RITA to the much larger aorta leads to poor patency. To overcome this technical limitation, we have used a modification that places the proximal end of this artery onto the hood of an accompanying vein graft at the aortic anastomosis instead of directly onto the aorta. We performed isolated coronary artery bypass grafting on 43 patients using the free RITA as a second arterial graft following pedicled left internal thoracic artery grafting. The mean patient age was 60 years and 38 patients were male. There was no mortality and no incidence of morbidity related to free RITA use. Postoperative coronary angiography performed in all patients revealed that all proximal anastomoses were widely patent, making the patency rate of the free RITA 100%. With these encouraging results, the free RITA graft with the described modification is thought to be a more promising second arterial graft with greater versatility than the pedicled graft. The long-term evaluation of a large patient population will determine the significance of this modification.