Microsurgical repair after crush-avulsion injury of the femoral vein in rats: prevention of microvascular thrombosis with recombinant human tissue-type plasminogen activator (rt-PA).

Vein thrombosis is often encountered in microsurgery, especially in the case of crush-avulsion injuries. The aim of this study was to investigate the effect of systemic administration of recombinant tissue-type plasminogen activator (rt-PA) on the patency of the femoral vein of the rat, which had previously sustained a crush-avulsion injury. The study consisted of 3 groups of male Wistar rats, 20 animals each. A standardized crush-avulsion injury model was used. After microvascular repair of the femoral vein, the animals received either normal saline (group A), heparin 100 U/kg body weight (group B), or rt-PA 3.5 mg/kg body weight (group C) systemically. Patency tests were performed at 20 minutes, 48 hours, and 1 week after blood flow reestablishment. According to our results, the patency rate of the rt-PA group was significantly higher than in both the control and heparin groups.     

Microvascular repair following a modified crush-avulsion injury in a rat model: effect of recombinant human tissue-type plasminogen activator on the patency rate

The failure rate of replantations following a crush-avulsion type injury is high. This study has been designed to reproduce an effective standardized crush-avulsion injury model to the femoral artery of the rat and evaluate the antithrombotic efficacy of systemic intravenous administration of recombinant human tissue-type plasminogen activator (rt-PA). The crush-avulsion injury was reproduced by using a bulldog clamp and two hemostats and followed by microvascular repair. The animals were divided into three groups of 20 rats each and received either normal saline, heparin 100 U/kg body weight, or rt-PA 3.5 mg/kg body weight intravenously. Patency tests were performed 20 min and 48 h after blood flow reestablishment. Results showed that this experimental crush-avulsion injury model ensures low patency in the control group, whereas systemic rt-PA administration improves the patency rate statistically significantly compared to control and heparin groups at both 20 min and 48 h postrevascularization.     

Composite grafting for distal digital amputation with respect to injury type and amputation level

Abstract

Purpose. This study evaluated the composite graft survival rate in distal digital amputations with respect to injury type and amputation level. Methods. Twenty-seven patients with complete fingertip amputations (32 digits) distal to the distal interphalangeal joint who were treated by composite grafting from January 2010 to February 2012 were enrolled. Injury type was classified as clean-cut, blunt-cut, or crush-avulsion. Amputation level was classified according to Ishikawa’s classification: subzones I–IV. Graft survival was categorised as complete, partial, or no survival. Results. The graft was more likely to exhibit complete survival in clean-cut injuries (50%) than in blunt-cut (10%) or crush-avulsion injuries (12.5%). However, when complete and partial survival were combined, there was no significant difference among injury types (clean-cut = 83.3%, blunt-cut = 70.0%; crush-avulsion = 68.8%). Composite grafting in sub-zone I provided good results (complete survival = 50%; partial survival = 50.0%; no survival = 0%). When complete and partial survival were combined, there was no significant difference with respect to amputation level except sub-zone I (II = 70.6%; III = 66.7%; IV = 60%). In sub-zone II, clean-cut injuries exhibited better graft survival than blunt-cut or crush-avulsion injuries. In sub-zones III and IV, no complete graft survival was observed. Conclusion. In conclusion, all types of injuries in sub-zone I and clean-cut injuries in sub-zone II are candidates for composite grafting. Blunt-cut and crush-avulsion injuries in sub-zone II are marginal candidates for composite grafting. Any type of injury in sub-zone III or IV is contraindicated for composite grafting and should be treated by microanastomosis.     

Microvascular repair with 1-mm polytetrafluoroethylene (PTFE) grafts: effect of recombinant tissue-type plasminogen activator (rt-PA) on the patency rate and healing process

The present study assesses the effect of recombinant tissue-type plasminogen activator (rt-PA) on the patency rate and healing process of microvascular polytetrafluoroethylene (PTFE) grafts. Wistar rats were used, divided into four groups of 25 animals each. After dissection of the carotid artery a segment of the vessel, 1 cm long, was resected and replaced by equal length graft. Two different type fibril length (30- or 60-microm) grafts of the same wall thickness (0.18 mm) were used. Normal saline or 3 mg/kg of body weight of rt-PA was applied locally in each group of different fibril length grafts. Patency tests were performed at 15 min and 4 weeks after blood flow was reestablished. All grafts were harvested and examined histologically. The results showed that local application of rt-PA improves patency statistically significantly in both types of fibril length grafts. Patency in 60-microm fibril length grafts was statistically significantly higher than that of 30-microm fibril length grafts, whether rt-PA was used or not. The use of rt-PA had no influence on the healing process of either type of graft.     

Glutaraldehyde-tanned microvascular grafts

In this study the efficacy of preserving microvascular heterografts with glutaraldehyde tanning was investigated. These were compared with glutaraldehyde-tanned autografts. Previous studies have found that untreated autograft veins maintain a 95% patency rate, whilst untreated heterograft veins (Group 1) had a 15% patency rate at 4 weeks in this study. Autogenous glutaraldehyde-tanned rabbit carotid arterial grafts (Group 2) and glutaraldehyde-tanned human chorionic veins (Group 3) were interposed in rabbit femoral or carotid arteries. Fifty per cent and 75% patency rates were achieved respectively at 4 weeks. The low patency rate of the autogenous group suggests that the glutaraldehyde tanning technique itself is largely responsible for the low patency of glutaraldehyde-tanned human chorionic veins rather than any immunological response. Therefore if human chorionic veins are to be used as a readily available preserved microvascular graft, further investigation is required to develop another technique which will reduce antigenicity without promoting thrombosis.     

Effect of thromboxane synthetase inhibition on canine autogenous vein grafts

This study examined the effect of an orally active thromboxane (TXA2) synthetase inhibitor (TSI) on the patency, TXA2 production, and platelet accumulation of reversed autogenous vein grafts. Ten dogs received TSI (U-63557A) 10 mg/kg po q8 hr for 6 weeks, beginning 24 hr prior to surgery, while 15 control dogs were untreated. One jugular vein was harvested and stored in 37 degrees C saline for 1 hr to induce mild endothelial injury (stored). Normal and stored jugular vein grafts (8 cm) were then implanted in opposite femoral arteries while 3-cm segments of the same veins were implanted in the carotid arteries. Femoral graft flow was restricted with a 5 Fr distal arterial stenosis and patency determined by arteriography at 1, 2, 4, and 6 weeks. Vein graft endothelial surface TXB2 production was measured by RIA at graft implantation and in carotid grafts harvested at 1 week. 111In-labeled platelets were given iv 24 hr prior to carotid graft harvest to determine graft-platelet deposition. TSI treatment improved early (1 week) femoral vein graft patency from 63 to 89% (P less than 0.05), a trend that persisted for 6 weeks. Warm saline storage reduced 1-week graft patency from 83 to 63% (P less than 0.05), a difference that decreased with time. TSI treatment resulted in a marked decrease in TXB2 production, but was not associated with decreased 111In-labeled platelet deposition in carotid vein grafts. Warm saline storage increased graft-platelet deposition which was predominant at the arterial anastomoses. TSI treatment may improve early vein graft patency during the transient period of endothelial injury.     

Modified crush-avulsion anastomosis model on the rat femoral vein

A crush-avulsion anastomosis model was established on the rat femoral vein. Saline or heparin was used as a luminal topical agent and was allowed to contact the damaged endothelium for 10 min. Patency and coagulation parameters were investigated for 1 week. The heparin treated group had a patency rate of 93% at 1 hr vs. 13% for the saline treated group (P<0.001). At 7 days, the heparin treated group had an 87% patency vs. 7% for the saline-treated group (P<0.001). Scanning electron micrography (SEM) provided evidence of the deposition of the components of early thrombosis in the crushed venous wall. In contrast, the SEM of the heparin treated group shows a paucity of any evidence of thrombus. These results indicate that the rat vein crush-avulsion model is a reliable and reproducible thrombosis model with low patency. The methods used with the topical agent may improve the patency rate in crush avulsion injuries. © 1995 Wiley-Liss, Inc.     

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.     

局部应用水蛭素对扩张皮瓣静脉淤血的防治

目的 探讨局部应用水蛭素对扩张皮瓣静脉淤血的防治作用。方法 以白色小型家猪为实验对象,将其模拟成扩张皮肤转移术后的淤血皮瓣,随机分成三组,A组（局部注射天然水蛭素,0.5 U/皮瓣）、B组（局部注射天然水蛭素,1 U/皮瓣）和对照组。进行大体观察、病理切片和ET-1、NO、TXB2的测定。结果 用药组（A组与B组间差异无显著意义）术后与对照组比较淤血消散快。光镜下用药组与对照组微血管淤血同期比较有明显差异。用药组的ET-1、NO、TXB2与对照组同期比较差异有显著意义（P＜0.05）。结论 水蛭素的局部应用对扩张皮瓣静脉淤血有明显的防治作用。     

Comparative results of carotid-subclavian bypass and axillo-axillary bypass in patients with symptomatic subclavian disease.

The results of 26 carotid-subclavian bypass (CSB) and 17 axillo-axillary bypass (AAB) procedures, performed to treat symptomatic lesions of the proximal subclavian artery, were reviewed. Nine graft failures (seven CSB and two AAB) occurred (mean follow-up: CSB = 60.5 +/- 41 months; AAB = 67.8 +/- 48 months). All CSB graft thromboses were observed in patients with an associated ipsilateral carotid lesion, surgically treated or not (p less than 0.05). Cumulative 5- and 10-year patency rates were 78.3 and 62.9% for the CSB group and 87.9% for the AAB group (N.S.). In patients with an associated ipsilateral carotid lesion, 5- and 10-year patency rates were 66.0% and 40.8% for the CSB group and 100% for the AAB group (p less than 0.05). Both the surgical procedures were safe and effective with excellent results in terms of operative mortality, major morbidity and long-term patency. CSB is the procedure of choice for the treatment of proximal subclavian artery disease for its physiological characteristics and for graft shortness. However AAB must be considered a suitable alternative and preferred when a concomitant ipsilateral carotid lesion is present. Recurrence of carotid stenosis or carotid lesion progression may cause the carotid-subclavian failure.     

Off-pump coronary artery bypass may decrease the patency of saphenous vein grafts

BACKGROUND: There is concern that a hypercoagulable status is caused after coronary artery bypass grafting without cardiopulmonary bypass (off-pump coronary artery bypass grafting, or OPCAB) and may potentially endanger the patency of the anastomosis. The aims of this study were: (1) to compare 1-year graft patency after OPCAB with that of conventional coronary artery bypass grafting (CABG) and that of on-pump beating CABG; and (2) to demonstrate any differences in patency of various conduits among the three groups. METHODS: We analyzed the results of 122 consecutive OPCAB cases (group 1) compared with those of 65 consecutive conventional CABG cases (group II) and those of 19 consecutive on-pump beating CABG cases (group III). In group I, coronary angiography (CAG) was performed immediately postoperatively and 1 year after surgery. In groups II and III, CAG was performed 1 year after surgery. Graft patency was graded as grade A (excellent), grade B (fair), or grade O (occluded). RESULTS: The average number of distal anastomoses in groups I, II, and III were 3.1 +/- 1.1, 3.7 +/- 0.9, and 3.6 +/- 0.9, respectively. In group I, postoperative CAG was performed in 92% of patients (112/122) before discharge. The patency rate (grade A + B) was 96.4% (162/168) for arterial grafts, and 85.6% (160/187) for saphenous vein grafts (SVG). One-year follow-up CAG was performed in 74% of patients (90/122). The patency rate was 97.8% (132/135) for arterial grafts and 67.9% (106/156) for SVG. In group II, 1-year follow-up CAG was performed in 65% of patients (42/65). The patency rate (grade A + B) was 93.5% (43/46) for arterial grafts and 88.3% (98/111) for SVG. In group III, 1-year follow-up CAG was performed in 89% of patients (17/19). The patency rate (grade A + B) was 100% (19/19) for arterial grafts and 86.8% (33/38) for SVG. CONCLUSIONS: Our results demonstrate that the patency rate ot SVG after OPCAB was significantly lower than that of arterial grafts in the early postoperative CAG (p < 0.001), and was also significantly lower than those of SVG of group II (p < 0.001) and group III (p < 0.01) in the postoperative 1-year CAG, although there was no significant difference in 1-year patency of arterial grafts among the three groups. Our data suggest that a specific perioperative anticoagulant therapy may be advisable in patients undergoing OPCAB with SVG.     

Benefits of arterial reconstruction in claudication

We conducted a midterm follow-up of 150 claudicants who underwent surgical reconstruction by assessing cumulative patency, survival, and palliation (graft patency in live patients) rates. Eighty-nine claudicants (group I) underwent direct (in situ) proximal revascularization, 33 (group II) had indirect (ex situ) proximal revascularization, while 28 (group III) had distal revascularization. The secondary patency rates at 3 years were 97.5% in group I, 97.0% in group II, and 75.0% in group III, respectively. Only one patient with limb graft thrombosis required below-knee amputation. There were 3 perioperative deaths (2 in group I and 1 in group II). The survival rates at 3 years were 86.0% in group I, 69.5% in group II, and 95.8% in group III, respectively. The palliation rates at 3 years were 84.8% in group I, 70.0% in group II, and 77.9% in group III, respectively. These findings indicate the midterm benefits of supra- and infrainguinal arterial reconstructions, and also suggest that the preoperative assessment of risks in individual patients, the selection of the appropriate operative procedure and graft material, and intensive postoperative follow-up and management of any associated disease are all important aspects in the treatment of claudicants.     

In search of the "perfect" anastomosis

Forty-five end-to-side microvascular anastomoses were completed in rat carotid arteries of 0.7-0.8 mm diameter (anastomosing the distal end of the left common carotid to the side of the right common carotid). For comparison both 10-0 and 11-0 sutures were utilized in different anastomotic techniques: interrupted, direct-continuous, and diagonal-continuous sutures, plus total mural thickness vs. partial mural thickness (piercing only the adventitia and outer media, excluding the intima). Anastomoses were evaluated for patency and scanning electron microscopic appearance after 10 to 12 weeks. The results indicate complete patency in all anastomoses. Ultrastructural observations revealed nearly normal intimal appearance in the partial medial technique and only minimal evidence of intimal injury in the other techniques. It is concluded that 100% patency can be obtained regardless of suture size or anastomotic technique. The most important factor in anastomotic patency is the operator's technical skill.     

Improving micrograft patency

To help clarify many of the controversial issues affecting early microvascular graft patency, a series of experiments was performed comparing the relative importance of graft material used alone and in conjunction with antiplatelet agents. Using a rat carotid model employing 1 cm micrografts with 1 mm luminal diameter, this study demonstrated that 1) untreated 1 mm polytetrafluoroethylene (PTFE) and human umbilical vein (HUV) micrografts have unacceptably low patency rates; 2) treatment with the antiplatelet agents indomethacin, ibuprofen, and aspirin significantly improved micrograft patency; 3) differences in patency among the three agents were not significant; and 4) PTFE had higher patency rates than HUV, although this difference did not achieve significance.     

A comparison of heparinised saline irrigation solutions in a model of microvascular thrombosis.

The use of heparinised irrigation solutions has become common in microvascular surgery, but the concentration of heparin has been determined empirically. A laboratory model of microvascular thrombosis, employing a crush injury, intimal abrasion, and stasis to the rat superficial femoral artery was used to compare heparinised saline irrigation solutions of various concentrations. The solutions included normal saline (Group I, controls) and heparinised normal saline in concentrations of 10 U/ml (Group III), 250 U/ml (Group IV), and 500 U/ml (Group V). Group I animals had a patency rate of 25% at 20 min and 0% at 24 h. Group II showed a patency rate of 75% at 20 min but fell to 37.5% at 24 h. Patency in Group III was 87.5% at 20 min and at 24 h. Group IV had a 100% patency rate at 20 min and at 24 h. Group V animals were 100% patent at 20 min and 87.5% patent at 24 h. The activated partial thromboplastin time was prolonged in animals exposed to 250 U/ml and 500 U/ml of heparinised saline. Patency was significantly improved in animals exposed to 100 U/ml, 250 U/ml and 500 U/ml when compared to the control group (p less than 0.001). These results suggest that topical heparinised saline administration is of benefit in the prevention of microvascular thrombosis. Higher concentrations tested in this study resulted in a significant increase in patency, but also prolonged the activated partial thromboplastin time. 100 U/ml is the ideal concentration of heparinised saline irrigation because it significantly improved patency but did not produce detectable systemic effects in this model.     

Dose responsive suppression of myointimal hyperplasia by dexamethasone.

The effect of increasing doses of dexamethasone on the development of myointimal hyperplasia in the rabbit carotid artery was studied by use of a balloon catheter injury model. Seventy New Zealand white rabbits underwent a standardized 2F balloon catheter stripping of the left carotid intima. The animals were randomly assigned to one of seven groups, each receiving daily injections of either saline (group I, N = 10) or graded doses of dexamethasone: 0.025 mg/kg (group II, N = 10); 0.050 mg/kg (group III, N = 10); 0.075 mg/kg (group IV, N = 10); 0.100 mg/kg (group V, N = 10); 0.125 mg/kg (group VI, N = 10); 0.150 mg/kg (group VII, N = 10). Injections were started 2 days before the intimal injury and continued daily, five times a week, for 8 weeks. The vessels were harvested 12 weeks after injury, and the ratio of the absolute area of intimal hyperplasia to the normalized area enclosed by the internal elastic lamina was measured as an index of myointimal hyperplasia. Also, at the time of harvest, blood flow (ml/min) was measured and the resistance delta P/flow (mm Hg/ml/min) calculated for each vessel in vivo. Twelve-week patency rates were 60% in the control group I, 90% in groups II and III, and 100% in groups IV, V, VI, and VII. The value for the intimal hyperplasia/internal elastic lamina index, expressed as a percent, was 22.2 +/- 3.7 for control group I, 17.7 +/- 2.1 group II, 14.8 +/- 3.0 group III, 12.8 +/- 2.4 group IV, 11.5 +/- 1.8 group V, 5.4 +/- 1.3 group VI, and 3.9 +/- 1.1 for group VII.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of arterial and venous patency in a rat model of subendothelium-stimulated thrombosis

The effectiveness of anticoagulants and platelet aggregation inhibitors was compared using comparable rat models of arterial and venous thrombosis. A mechanical endothelium-denuding injury was created on the lumenal surface of donor Lewis rat carotid arteries. These were cut into 4–5 mm lengths and grafted into femoral veins and arteries of recipient syngeneic rats using microvascular anastomotic techniques. Recipients received either systemic heparin, or aspirin with dipyridamole, or saline (control). In the arteries, the 1-day patency rate was 94% in the heparin-treated rats, but only 50% in the aspirin/dipyridamole group and 44% in the control group. The venous patency rate was 56% in the heparin group, 31% in the aspirin/dipyridamole group, and 0% in the control group. This unique model for comparing thrombosis in arteries and veins shows that anticoagulation is more effective than inhibition of platelet aggregation in the rat arterial system, with less of a differential effect in the venous system. © 1997 Wiley-Liss, Inc. MICROSURGERY 17:226–229 1996     

Microvascular grafts: effect of diameter discrepancy on patency rates

This study examined the effects of diameter discrepancy between interpositional vein grafts within a range of 0.25 to 2 mm. One hundred rats underwent isolation of a 10 mm segment of the femoral artery, from which a 4 mm segment was removed. Venous grafts measuring 8 +/- 2 mm were interposed. The rats were categorized by their graft to artery diameter ratios. Patency was assessed upon completion and 4-6 days postoperatively. All surgical specimens were submitted to the pathology department for microscopic evaluation. Results showed Group I: graft to artery ratio 1:1, patency rate 90% (18/20); Group II: ratio 0.75:1, patency rate 80% (16/20); Group III: ratio 0.5:1, patency rate 60% (12/20), Group IV: ratio 0.25:1, patency rate 20% (4/20); Group V: ratio 2:1, patency rate 60% (12/20). It is concluded that 1:1 venous graft to artery ratios are optimal. When this is impossible, diameter discrepancies should be at least 0.75:1 for acceptable patency rates to be attained in microvascular grafting.     

Effect of blood flow rate and donor vessel diameter on the patency of carotid venous bypass grafts in dogs

A saphenous vein graft was implanted from the right subclavian to the right common carotid artery in seven dogs (group I) and between the right and left common carotid arteries in another seven dogs (group II). The recipient artery was ligated proximally to augment blood flow through the graft. Immediately after the anastomoses were completed, the average blood flow through the graft was 32 +/- 25 mL/min in group I and 122 +/- 22 mL/min in group II. At sacrifice 30 days later, angiography showed that all grafts in group I were thrombosed, whereas six (87.5%) of seven grafts in group II were patent. These findings suggest that a larger donor vessel diameter and higher graft flow rates may improve patency in venous bypass grafts that are 3 to 5 mm in diameter.     

Local pulmonary activation of proteolytic enzymes after Escherichia-coli-induced lung injury in sheep

Activation of several cascade systems, e.g. coagulation, fibrinolysis, kallikreinkinin, complement and eicosanoid systems, has been implicated in the etiology of septic-lung microvascular injury. A chronic lung lymph fistula preparation in sheep (n = 9) was used to study coagulation, kallikrein-kinin and eicosanoids during Escherichia coli septicemia. Lung lymph flow and lymph composition indicated an increased lung microvascular permeability approximately 2 h after infusion of bacteria. Stable prothrombin and antithrombin III levels in lymph contradicted local activation of the coagulation cascade in the lung and systemic activation was not evident until 4 h after bacteria infusion. Lymph thromboxane B2 and 6-keto PGF1 alpha peaked early (1 h). Reduced lymph prekallikrein and kallikrein inhibitors indicated local activation of this system in the lung. Systemic activation of kallikrein could not be demonstrated. Thus, (1) changes in systemic blood may not adequately reflect local events and (2) studies of proteolytic enzymes and other inflammatory mediators in lung may contribute to clarifying the etiology of microvascular injury.