静脉皮瓣成活过程的实验研究

我们以兔为实验动物，通过微循环观察及血管内灌注填充剂，研究静脉皮瓣的成活过程。这一过程可分为２个阶段。第一阶段（术后７２小时内）为静脉血营养期：静脉血由静脉干通过脉吻合支、微静脉干间吻合支及终末微静脉吻合支回流至另一静脉。术后４８小时内毛细血管内无血液运动。第二阶段（术后７２小时～６周）为动脉血营养及血管改造期：术后７２小时新生血管开始向皮瓣内生长。术后７２天皮瓣动脉同主要来自皮瓣周围正常组织内的     

静脉皮瓣成活过程的实验研究

我们以兔为实验动物,通过微循环观察及血管内灌注填充剂,研究静脉皮瓣的成活过程。这一过程可分为2个阶段。第一阶段(术后72小时内)为静脉血营养期:静脉血由静脉干通过小静脉吻合支、微静脉干间吻合支及终末微静脉吻合支回流至另一静脉。术后48小时内毛细血管内无血液运动。第二阶段(术后72小时～6周)为动脉血营养及血管改造期:术后72小时新生血管开始向皮瓣内生长。术后72天皮瓣动脉同主要来自皮瓣周围正常组织内的新生血管吻合使动脉血分布于整个皮瓣,这是静脉皮瓣成活的关键。     

皮神经伴行血管皮瓣内浅静脉干不同处理方法的临床研究

目的 探讨皮神经伴行血管皮瓣内浅静脉干不同处理方法对皮瓣的影响。方法 对137例手、足软组织缺损的患者，分别采用带桡神经浅支、尺神经手背支及腓肠神经伴行血管为主的筋膜蒂逆行岛状皮瓣，术中对皮瓣内浅静脉采取静脉干不结扎、结扎组和吻合等三种不同的处理方法。结果 术后浅静脉干不结扎组（27例），皮瓣出现不同程度的水泡、肿胀、青紫色，术后第7天皮瓣远端部分坏死。结扎组（87例）和吻合组（23例），术后皮瓣无静脉危象出现，两组皮瓣全部成活。结论 对皮神经伴行血管皮瓣内浅静脉干吻合是三种术式中最理想的方法，而对浅静脉干结扎是三种中最实用、有效的方法。     

跨区供血皮瓣成活过程中血管构筑及内源性VEGF变化的实验研究

目的：探索跨区供血皮瓣的成活机制。方法：以大鼠旋髂深动脉为蒂制作包含肋间后动脉支配区域的右侧背部矩形跨区供血皮瓣，分别于术后即刻，术后1，2，3，5，7天时，观察皮瓣成活情况，成活过程中血管构筑及蒂部血管口径的改变以及内源性血管内皮细胞生长因子（Endogenous Vascular Endothelial Growth Factor，VEGF）免疫组化染色（取材部位为两血管支配区域中间血管网吻合部）。结果：皮瓣完全成活率100％。轴心动脉经吻合支向远端供血，经静脉吻合支回流。血管吻合区以远的血流方向与术前相反。术后即刻VEGF免疫组化染色阴性；1天后血管吻合支与术前相比明显增多、增粗，蒂部血管口径明显增粗，VEGF免疫组化染色阳性区域较多；3天时上述指标达高峰；7天时形成与顺流皮瓣相似的轴心血管，蒂部血管口径有所下降，VEGF免疫组化染色阴性。结论：跨区供血皮瓣的成活机制为血管的口径增大及数量增多，最终形成轴形血管皮瓣。内源性VEGF对皮瓣的成活起重要作用。     

前臂动脉化静脉皮瓣的临床应用

我院应用４例前臂动脉化静脉皮瓣及离体标本的灌注，探讨了此皮瓣的血循环机理。动脉血经静脉支部分直接回流，部分进入微静脉经毛细血管达真毛细管网。另部分动脉血入微静脉经动静脉吻合支返回微动脉入后微动脉再入真毛细血管网。因静脉瓣的阻碍，使引流侧皮瓣远端灌流困难，易造成缺血坏死而灌流侧易成瘀血性坏死。因此理想血供应是动脉化干及引流干均应顺静脉血流方向缝接，减少静脉瓣阻力。动脉化静脉皮瓣易发生肿胀、充血、瘀血     

动脉化静脉皮瓣坏死原因的探讨及皮瓣改造

应用微循环显微镜活体观察动脉化静脉皮瓣，发现术后早期皮瓣微血管绝大部分处于关闭状态，原因与静脉短路循环，高压高氧动脉血损伤微血管内上以细胞以及微血栓形成等有关。７２小时后微血管灌流明显改善，根据皮肤扩张器能增组织血管密度，以及静脉内皮细胞对动脉血流需逐渐适应的特点，对皮瓣进行改造后，其成活率明显提高。     

改良腓肠神经营养血管皮瓣修复足背软组织缺损

目的总结吻合小隐静脉的远端蒂腓肠神经营养血管皮瓣修复足背软组织缺损的经验，探讨本术式皮瓣的血循环特点、成活机制及术中注意事项。方法对2003年10月-2007年6月采用吻合小隐静脉的远端蒂腓肠神经营养血管皮瓣修复足背软组织缺损20例的病例资料进行回顾性分析，该20例足背均为不同程度的软组织缺顺，术中将皮瓣近端小隐静脉与受区大隐静脉或其属支吻合。结果20例术后皮瓣均成活，无静脉回梳障碍等并发症发生。仅1例远端部分坏死，经换药后愈合。术后随访6个月～4年，足部外形良好，皮瓣质地、色泽与周边相似，足功能恢复良好。结论吻合小隐静脉改善了腓肠神经营养血管皮瓣静脉回流，为皮瓣建立了通畅的静脉回流系统，改变了皮瓣血液循环模式，扩大了皮瓣的修复范围及能力，可使皮瓣向肢端延伸，能够修复足背远端软组织缺损，为临床修复足中远端软组织缺损提供了一种新方法。     

动脉化静脉皮瓣坏死原因的探讨及皮瓣改造

应用微循环显微镜活体观察动脉化静脉皮瓣，发现术后早期皮瓣微血管绝大部分处于关闭状态，原因与静脉短路循环，高压高氧动脉血损伤微血管内皮细胞以及微血栓形成等有关。７２小时后微血管灌流明显改善，根据皮肤扩张器能增加组织血管密度，以及静脉内皮细胞对动脉血流需逐渐适应的特点，对皮瓣进行改造后，其成活率明显提高     

浅静脉皮神经营养血管蒂逆行皮瓣修复手部皮肤缺损

目的报道三种吻合浅静脉的皮神经营养血管蒂逆行岛状皮瓣转位术的临床疗效.方法从1998年7月～2001年3月应用三种吻合浅静脉的皮神经营养血蒂管皮瓣修复手部皮肤软组织缺损16例,皮瓣最大面积20cm×8cm,最小面积4cm×3cm,其中头静脉桡神经浅内侧支营养血管皮瓣4例,贵要静脉前臂内侧皮神经营养血管皮瓣5例,头静脉前臂外侧皮神经营养血管皮瓣7例.结果 16例皮瓣均顺利成活,皮瓣未出现明显肿胀及瘀血.结论皮神经营养血管皮瓣逆行转位后,吻合一条浅静脉对皮瓣的顺利成活、肢体的静脉回流及皮瓣的超大面积切取具有积极的意义.     

跨区反流轴型皮瓣成活机理的实验研究

目的了解反流轴型皮瓣的成活机理. 方法以Wistar大白鼠左旋髂深血管为蒂,形成8.0 cm×2.5 cm横跨腰背部中线4.0 cm的矩形皮瓣,作为反流轴型皮瓣模型,观察其成活过程中动脉供血和静脉回流的途径、方向和流速、血管管径和管内压力、血流量及血管构筑的改变. 结果皮瓣完全成活率100%,术前中线两侧动脉压差约等于0,术后皮瓣近、远端灌注压差达4.9 kPa;轴心动脉经中线吻合支向对侧供血,经静脉吻合支回流;中线以远区域的血流方向与术前相反.术后48 h内,皮瓣远端血流量仅为术前的1/8～1/5,中线区静脉压高于远端,6例的皮瓣远端静脉淤血;72 h后中线区血管吻合支增多、增粗,静脉压低于远端,远端淤血开始缓解;轴心血管沿吻合支逐渐向中线以远延伸,14 d形成与顺流皮瓣相似的轴心血管,血流量基本恢复到术前水平. 结论反流轴型皮瓣经两侧轴心血管之间的吻合支供血和回流,其动力是吻合支两侧的动、静脉压差.术后72 h内易出现静脉回流障碍,此期皮瓣以代偿性的吻合支增粗、增多及压力下降维持其循环;72 h后,与顺流轴型皮瓣相似的轴心血管逐渐形成, 为皮瓣成活提供了可靠的循环.     

小腿火器伤严重组织缺损桥式肌皮瓣移植修复

目的：探讨小腿火器伤严重组织缺损采用游离组织移植修复而受区无供血血管可供缝接时的解决方法。方法：在形态学及动脉压和血流量测定的基础上,设计以健侧胫后血管形成一顺行皮瓣桥作为血管蒂携带游离肌皮瓣移植修复。结果：７例小腿火器伤严重软组织缺损伤者采用皮瓣桥携带的肌皮瓣均成活,创面一期修复;同时有２例伴胫骨缺损,采用对侧游离腓骨移植一期修复,经Ｘ线检查均骨愈合。结论：以健侧胫后血管作为游离组织移植时的供血血管是解决小腿火器伤严重软组织缺损且受区无供血血管可供缝接时的一种理想修复方法;局部软组织条件改善、丰富的血循环是同期游离腓骨移植修复胫骨缺损骨愈合的基础。     

Free flap neovascularization: myth or reality?

The blood supply of 17 free flaps was studied several months after surgery. The aim was to see whether or not the free flaps acquired blood flow through vessels across the flap inset independently of the main vascular anastomoses. A color Doppler flowmeter was used to identify the original arterial and venous anastomoses, the vessels in the margin of the flap, and also across the flap inset. The main vascular pedicle was then manually compressed for 2 min and blood flow was again examined in the vessels at the margin of the flap. The flap vessels (post-anastomotic), the anastomoses, and the recipient vessels (pre-anastomotic) could be identified in every case. There was no evidence of anastomotic stenosis. No vessels (neo-vascularization) greater than 0.5 mm could be identified across the flap inset. Small arteries could be identified in the flap near the inset. These vessels emptied completely on manual compression of the vascular pedicle for 2 min and did not refill until the compression was released. This evidence suggests that the free flaps do not receive significant blood flow through vessels across the flap inset, and are therefore significantly dependent for vascularity on the original anastomoses even 1 year after surgery.     

Microcirculation in unphysiological flaps at early stage after operation: an experimental study]

Microcirculation and blood perfusion in unphysiological flaps were observed with rabbit ear microcirculation chamber. The microcirculation of the venous flap in two days after operation was reestablished mainly by diversion of blood flow through the "to and fro" movement of venous blood. Arteriovenous anastomoses were gradually opened, resulting in the microcirculation to restore normal perfusion, venous blood through the anastomoses into arteriole then to capillaries. The microcirculation of arterialized venous flaps was almost the same as that of the venous flaps. In two days after operation, the diversion of blood flow perfused the capillaries under high pressure, so that the flow velocity and rate were much faster and larger than those of the venous flaps. The microcirculation of venouslized arterial flap, nourished by venous blood through the arterial system, was the same as that of the physiological flap. But the capillaries were perfused venous blood flow, and the blood flow velocity and rate were much slower and smaller than those of the physiological flap.     

Effect of sequence,timing of vascular anastomosis,and clamp removal on survival of microsurgical flaps

The effects of the timing and order of clamp removal in microsurgical transplants were studied in rat groin skin flap and rat latissimus dorsi muscle flap models. Forty rats were divided into four groups. In Group 1, the arterial pedicle of the skin flap was anastomosed first, and the clamp was released after the anastomosis was completed. The venous pedicle was then repaired after inflow was restored. In Group 2, the venous pedicle of the skin flap was anastomosed first. The venous clamp was not released until completion of the arterial anastomosis. In Group 3, the arterial pedicle was anastomosed first in the muscle flap. The venous anastomosis was then performed after the arterial clamp was released. In Group 4, the venous pedicle was anastomosed first, and both clamps were released simultaneously. The blood perfusion of the skin flaps was examined after both clamps were released in Groups 1 and 2. The flap survival status was examined 5 days postoperatively for skin flaps and at 3 days for muscle flaps. Skin flaps in an additional six rats were harvested for histology. The results showed that the flap blood flow for Group 1 was statistically significantly higher than for Group 2 flaps in the first 20 min after reperfusion. There was no significant difference of flow between these two groups during the 30 to 90 min after reperfusion. The difference in survival rates for the four groups was not significant. Histology revealed extensive congestion in the flaps from Group 1 after completion anastomoses, but the congestion was significantly decreased at 3 hr following reperfusion. In conclusion, a brief venous stasis during anastomosis, after establishment of arterial inflow, is not detrimental to flap survival. The sequence of anastomosis will not affect outcome for either the cutaneous flap or the muscle flap models. Early flap perfusion was increased when the arterial anastomosis was performed first.     

Microvascular histopathology in head and neck oncology.

A histological study of both recipient and flap vessels was performed in 30 patients with head and neck cancer, and relevant preoperative risk factors were assessed. A total of 35 free flaps were transferred in 30 patients; 16 patients had preoperative radiotherapy, 13 were smokers, eight had hypertension and six had peripheral vascular disease. No significant venous pathology was found in either the flap or the neck veins. However, over two-thirds of the neck arteries and one-half of the flap arteries were found to have microscopic arterial pathology. The only pre-existing factor significantly influencing vessel pathology was hypertension (P=0.007). All flaps survived, although in two there was some loss of the skin paddle. This study reveals that the majority of patients undergoing microsurgery in the head and neck region have pre-existing arterial damage in both the flap and the recipient arteries, but this does not have a significant effect on the overall patency of the microvascular anastomoses.     

Influence of topical heparin on stasis-induced thrombosis of microvascular anastomoses.

An experiment was done to determine whether topical heparin and the association of anastomoses with dependent tissue (free flaps) exert any influences on stasis-induced microvascular thrombosis. Rat femoral vessel anastomoses with or without free flap construction were used in a total of 50 male Sprague-Dawley rats. Saline either with or without heparin was used for intralumenal irrigation during the anastomosis. Following anastomotic repair, the femoral vessels were reclamped, inducing stasis for either 2 or 4 hr. Our results showed that static blood had little adverse effect on thrombosis at the arterial anastomosis when reclamped for up to 4 hr in both standard and flap-associated anastomoses. Topical heparin significantly reduced the incidence of stasis-induced thrombosis of venous anastomoses. The venous patency rates in standard anastomoses were lower than those in flap-associated anastomoses after both 2 and 4 hr of stasis. From these results, we conclude the following. 1) Arteries may be reclamped for up to 4 hr without detriment despite static blood being in contact with the anastomotic site. 2) Topical heparin may be helpful in increasing the patency rate of venous anastomoses after a period of blood stasis. 3) Free flap construction may play a role in decreasing stasis-induced microvascular thrombosis.     

Can a true perforator flap survive on venous blood? A case report of anterolateral thigh true perforator flap supplied by antegrade venous inflow

In some cases of degloving injury, as a result of multiple venous anastomoses formed on the peripheral and proximal sides, the detached flap skin did survive, though with patchy necrosis. On the basis of this experience, the skin and soft-tissue defects after removing skin cancer were closed with an anterolateral thigh true perforator flap, measuring 4 × 5 cm in size, which is nourished by venous blood. The subcutaneous vein on the peripheral side of the defect was anastomosed to the perforator artery, and the veins on the proximal side of the defects were anastomosed to the concomitant veins of the perforator. After surgery, to ensure a sufficient blood flow to the flap, the affected limb was positioned lower than the heart for 1 week. To prevent microthrombus in the perforator branch and the flap, preventive anticoagulant therapy was performed. The transplanted flap had marked cyanosis for a few days, but turned pinkish on the sixth day after surgery. The flap survived completely. As opposed to venous flaps reported in the past, the physiologic direction of blood flow of the flap is from arteries to veins, and it is nourished exclusively by venous blood. If a flap is small, and there are no appropriate recipient vessels nearby, this method could serve as a favorable alternative.     

Arterialized venous perfusion of composite tissue

The results of our experiment prove that arterialized venous perfusion is a viable means of nourishing complex composite tissue without using the arterial tree. Previous laboratory findings, coupled with the results of this experiment, demonstrate that as long as proximal arterial inflow is ensured, both the arterial and venous trees need not be intact to keep tissue alive. Rather, it seems that the prerequisites for tissue survival are that at least one of the two systems be intact and that there be sufficient inflow and outflow channels available. Whether these channels are arteries or veins is probably not important. The use of properly placed efferent or afferent arteriovenous fistulas allows one system to provide both physiologic functions. Whether the efferent arterial anastomosis stays open over the long term appears to be inconsequential. Survival is ensured by either direct perfusion with oxygen delivery through the venous tree or through the eventual ingrowth of recipient vessels into the flap by way of the delay phenomena. This perfusion technique is ideally suited for tissue with an inadequate arterial tree but with an intact venous system devoid of venous valves (most veins less than 1.5 mm in diameter). A well-vascularized recipient bed capable of providing vessel ingrowth into transferred tissue may be important in the case of delayed arteriovenous fistula occlusion secondary to intimal hyperplasia; therefore, further experimental study of these flaps must be undertaken before arterialized venous flaps can be recommended for placement in recipient sites compromised due to radiation, ischemia, diabetes, or other causes of small vessel disease in the recipient bed. Although efferent arteriovenous fistulas are currently used to provide arterialized venous perfusion in selected cases of end stage arterial occlusive and vasospastic disease, perhaps their greatest role is in the management of tissue transfer with an inadequate arterial tree. Much knowledge must be gained to understand the physiologic principles and requirements for optimal perfusion. Many questions are left unanswered. For example, in those arteriovenous fistulas that narrow or occlude secondary to neointimal hyperplasia or other causes, which channels (veins or arteries?) are used for perfusion during recipient vessel growth? Can intimal hyperplasia be reversed or prevented by drug therapy and would this be advantageous? Can venous valves be made incompetent so that this technique can be used for larger vessels?(ABSTRACT TRUNCATED AT 400 WORDS)     

Clinical experience with non-penetrating vascular clips in free-flap reconstructions.

To date, the gold standard for performing a microvascular anastomosis has been the penetrating suture with attached needle. During the last two decades, non-penetrating techniques have been introduced, including the Unilink system for end-to-end anastomoses, and the VCS clip-applier system for both end-to-end and end-to-side anastomoses. The aim of this study was to compare the results of different techniques used to create microvascular anastomoses in free-flap reconstructions. Between January 1995 and October 1999, we performed 474 microvascular anastomoses in 216 consecutive free-tissue transfers. The anastomosis techniques included manual sutures (42%), Unilink rings (34%) and VCS clips (24%). Seven combined sutured-clipped anastomoses were excluded from further analysis. The mean anastomotic time when rings were applied was significantly shorter than when using clips (P 0.0001) or sutures (P 0.0001). Venous anastomoses using clips took less time than those using sutures (P 0.05). There were 19 anastomotic failures, all of which lead to early flap failure. Ten flaps were salvaged by early reoperation; nine flaps were lost. Three more flaps were lost as a result of other causes, bringing the flap survival rate down to 94.4%. Early flap failure was caused by failure of the arterial anastomosis in eight cases; all of them were sutured (these represented 5% of all arterial anastomoses with sutures). None of the clipped arterial anastomoses failed. Early flap failure was caused by failure of the venous anastomosis in 11 patients. Three of these anastomoses were sutured (representing 6% of all venous anastomoses with sutures), seven were anastomosed with rings (representing 5% of all venous anastomoses with rings) and one was clipped (representing 2% of all venous anastomoses with clips). Both the VCS clip-applier system and the Unilink system are easy to handle and allow fast microvascular anastomoses without intraluminal penetration. The patency rate of clipped vessels is at least as good as the patency rates of vessels anastomosed using sutures or rings.     

Microcirculation of a venous flap: an experimental study with microspheres in rabbits.

In recent years, it has been found that maintenance of venous circulation alone may support a small flap with no direct arterial inflow. The clinical application of a venous flap has potential in the field of microsurgery. The purpose of this study was to evaluate the haemodynamics within a pedicled venous flap in rabbits, compared with those of a composite graft. Pedicled venous flaps and composite grafts were raised from the abdominal walls of 30 adult New Zealand rabbits. Flap survival was measured and recorded and blood flow studies with microspheres were done for seven days. The viability of the pedicled venous flaps was much better than that of the composite grafts. At two weeks 24 of the venous flaps (80%) showed more than 75% surviving, but 29 (97%) of the composite grafts had less than 25% surviving. The results suggest that the blood flow through a patent vein maintained in a venous skin flap can provide enough nutrients for the flap to survive during the initial three days until neovascularisation. The venous flap receives more blood flow than a composite graft. We conclude that a venous flap depends on blood supply from the axial vein in addition to neovascularisation to maintain its survival.