Emergency hepato-renal artery bypass using a PTFE graft

A 51-year-old patient suffering from Buerger's disease with bilateral lower limb amputation and Leriche syndrome presented with uncontrollable hypertension and renal failure caused by right renal artery subocclusive stenosis associated with an occluded left renal artery and atrophic kidney. He underwent a right hepato-renal bypass grafting using an externally supported polytetrafluorethylene (PTFE) graft. Renal function improved markedly and hypertension could be controlled by standard antihypertensive treatment. Normal right renal function was maintained at one-year follow-up.     

Tissue engineering a clinically useful extracellular matrix biomaterial

Implantable biomaterials are one of the most useful tools in the surgeon’s armamentarium, yet there is much room for improvement. Chronic pain, tissue erosion, and late infections are just a few of the serious complications that can occur with conventional, inert materials. In contrast, tissue-inductive materials exist today. Combinations of biologically important molecules for directing cell growth and providing structural stability can be found in naturally occuring extracellular matrices. These “soft-tissue skeletons” of Mother Nature can be harvested, processed, and provided in a medically safe and biologically active form for repairing many different tissues in the human body. The future of surgical practice may well be determined by how well these new implant materials recreate the tissues they replace.     

Trichosporon asahii infection of a dialysis PTFE arteriovenous graft

Trichosporon species are the causative agents of superficial skin infections, such as white piedra. Immunocompromised hosts, particularly those with underlying hematological malignancy, are at risk of developing invasive infection, which usually progresses to disseminated life-threatening disease. Peritonitis caused by Trichosporon has been described in end-stage renal disease patients treated with continuous ambulatory peritoneal dialysis. Here, we report on a Trichosporon infection of an arteriovenous graft in a patient on chronic hemodialysis. The infection was successfully treated with fluconazole and total surgical resection of the graft.     

Small intestinal submucosa as a large diameter vascular graft in the dog

Autogenous saphenous vein and synthetic materials, such as Dacron and expanded polytetrafluoroethylene, have been used extensively as vascular grafts with moderate success. Improved success rates for vascular graft surgery may be possible if superior graft material was available. We tested the use of autogenous small intestinal submucosa (SIS) as a large diameter (10 mm) vascular graft in the infrarenal aorta of 12 dogs. One dog died with graft thrombosis within 48 hr of surgery. Nine dogs were sacrificed at various times during a 52-week post-surgical period and showed patent grafts without infection, thrombosis, intimal hyperplasia, or adverse effects upon blood pressure. There was no ultrastructural evidence of endothelial cell growth on the luminal surface of the SIS graft which was composed of a dense, non-thrombogenic, organized collagenous connective tissue. The SIS material was approximately one order of magnitude less elastic than natural aorta and showed an immediate dilatation of approximately 18% after exposure to the systemic blood pressure. However, there was no progressive dilatation during the 52-week postsurgical period. Two dogs remain alive at 8 and 52 weeks post-surgery with patent grafts as determined by positive contrast radiography and Doppler studies. We conclude that autogenous small intestinal submucosa can be successfully used as a large diameter arterial graft in the dog and is worthy of further investigation.     

The patient with a clotted PTFE graft developing fever

Haemodialysis access graft infection is easily recognizable when local symptoms (warmth, swelling, pain, or drainage) predominate, and endocarditis is a well established complication of infected grafts. We report a case of bacterial endocarditis complicating silent infection in clotted haemodialysis access graft. It is suggested that, clotted non-functioning grafts may be the harbingers of silent infection, and should be suspected as the source of infection in every haemodialysis patient that presents with fever, even in the absence of clinical signs of graft site infection.     

A new vascularized bone graft transferred by microvascular anastomosis as a free flap

We describe a new, versatile bone and soft tissue compound free flap which may be transferred quickly and simply and describe its use in the treatment of compound fracture of the tibia and fibula with non-union due to loss of bone. The iliac crest and overlying soft tissue is transferred to the leg in one stage by microvascular anastomosis of the deep circumflex iliac vessels to vessels in the leg.     

Vascular diameter determining the magnification for a microvascular anastomosis

The purpose of this study was to determine the association between vascular diameters and amount of magnification and to assess the influence of the magnification media on the microanastomosis quality and permeability. Sixty arterial microanostomoses were distributed into three groups: group I (diameter 1.5 mm), group II (1.5 to 2.5 mm), and group III (> 2.5 mm). The models used were carotid artery of Sprague-Dawley rats and carotid and abdominal artery of wild rabbits. In each group, 10 anastomoses were performed with 2.5 x loupes and 10 with 10 x microscope. The total time of anastomosis, the quality of the anastomosis (Gorman scale), and 24-hour permeability rate were measured. The total anastomotic time and quality had statistical differences for the microscope by analyzing the total sample and group I only. The global permeability was 83% for the microscope and 40% for the loupe. The same result was observed in group I but no differences were observed in the other groups. The histology and the survey showed similar results. Microanastomoses performed under a microscope (10 x) were performed in less time, were of better quality, and had higher permeability rates when compared with those performed under a loupe (2.5 x). In vessels < 1.5 mm, these differences were statistically significant but in vessels > 1.5 mm no differences were observed.     

Surgical experience with expanded polytetrafluoroethylene (PTFE) as a replacement graft for traumatized vessels.

With the increased nationwide incidence of major vascular injuries, the need for interposition grafting has become quite common in major trauma centers. Despite extensive experience with such injuries, the choice of a substitute conduit remains controversial. Recent studies have demonstrated the potential of expanded polytetrafluoroethylene (PTFE) as a replacement graft for small arteries and veins. The surgical services at the Ben Taub General Hospital began to use PTFE grafts in traumatic vascular wounds approximately 2 years ago. Eight axillary arteries and 12 brachial arteries have had interposition grafting with PTFE prostheses. Eleven patients have required PTFE interposition grafts in repair of traumatized common, superficial, and profunda femoris arteries and common femoral veins; eight patients had reconstruction in the popliteal artery or vein. Three patients had renal artery revascularization procedures following blunt abdominal trauma, three patient had segmental replacement of the superior mesenteric artery following gunshot wounds, and one carotid artery, one iliac vein, and two axillary veins were grafted with PTFE. All patients with segmental repair of axillary, brachial, femoral, and popliteal vessels have maintained good distal pulses and viable extremities. No grafts have thrombosed, nor become infected, in spite of soft-tissue injury encountered at time or repair. In situations requiring interposition graft placement for reestablishment of distal flow in small arteries and veins, PTFE grafts appear to be an acceptable prosthesis.     

Expanded polytetrafluoroethylene as a microvascular graft: An experimental study

The patency rates of expanded polytetrafluoroethylene (PTFE) vascular grafts with internal diameters of 1.0–3.0 mm were evaluated in three different species (dogs, rabbits, and rats). An overall 2-week patency rate of 14 (23%) of 60 was obtained, with the exception of 10 (83%) of 12 grafts 1.8 mm in diameter inserted in the carotid arteries of rabbits. The presence of numerous variables in the structural properties of PTFE may explain the variable results reported in the literature and this study. Heparinization did not improve the results, nor did modification in suture technique. At the present time, PTFE cannot be considered an equivalent to or a substitute for autogenous vein grafts in microvascular surgery.     

Relapsing seroma in a uremic patient bearing a PTFE graft as vascular access

Seroma is one of the most frequent complications of PTFE vascular grafts and its etiology is still unclear. Case report: A 51 year-old male on regular dialytic treatment for seven years underwent the surgical implantation of a vascular prosthesis of homologous safena due to the thrombosis of his native artero-venous fistula. Several years earlier the patient had suffered the amputation of the left forearm because of electric shock. A few months later the vascular prosthesis was replaced with a PTFE vascular graft as a result of aneurysm formation and thrombosis. During the following days a non pulsating swelling occurred near the arterial anasto-mosis. Ultrasonography, doppler sonography and aspiration confirmed the diagnosis of seroma and it was surgically removed. Some weeks later a new seroma was observed in the same site and associated with a skin ulcer. A new surgical removal had no benefit and about one month later a perigraft collection was found along with signs of bacterial infection. For this reason the patient underwent the surgical excision of the PTFE graft and a vascular access was warranted by placing a Tesio TM catheter. Usually surgery is considered mandatory in seromas larger than 2 cm in diameter and showing continuous growth. In our patient the poor vascular status might have suggested a more conservative management even with a seroma diameter of about 7 cm. Nevertheless the high risk of systemic infection prompted us to remove the PTFE graft.     

Experimental evaluation of small intestinal submucosa as a microvascular graft material

The evaluation of porcine small intestine submucosa (SIS) in a microsurgical model was conducted using an interpositional graft in the rat femoral artery. The SIS grafts were fabricated from processed porcine material that was wrapped around a glass tube and oversewn longitudinally to produce a tubular structure. Of the 42 animals studied, 7 received grafts of untreated SIS (group I), 7 of the grafts were presoaked (PSH) in heparin (Group II), 7 animals were treated with systemic heparin prior to implantation of PSH-SIS (group III), 7 animals received SIS grafts crosslinked to heparin (group IV), 7 animals received SIS grafts crosslinked to urokinase (group V), and 7 animals received untreated autologous epigastric vein grafts (group VI). Patency was assessed postoperatively and selected grafts were evaluated by histology. All SIS grafts failed to maintain patency beyond the first postoperative hour. Histologic examination of the thrombosed graft surfaces revealed a smooth luminal surface with a thick layer of attached fibrin and platelets with a central occluding thrombus. The thickness of the induced fibrin layer appears to narrow intraluminal space significantly at the microvascular level. While having excellent success at vessel diameters greater than 3 mm, and in a variety of nonporcine animal models without xenographic rejection, SIS in this model was thrombogenic despite a favorable surface morphology as demonstrated by SEM. Even with use of heparin and urokinase SIS graft thrombosis occurred. © 1994 Wiley-Liss, Inc.     

Rat epigastric pedicle model: a clinically relevant evaluation of 1-mm PTFE grafts

Twenty-eight Sprague-Dawley rats had 1.0-mm polytetrafluoroethylene (PTFE) interposition grafts placed in their femoral artery that supplied a 3.0 X 3.0 cm epigastric pedicle flap. The model is the first to evaluate 1.0-mm PTFE under rigorous, clinically simulating conditions. Anastomoses employed a new, continuous telescoping suture technique. Grafts were selected for histological and electron microscopic evaluation, which confirmed the development of a cellular neointimal lining. Viability of the flap model had a 90% correlation with graft patency. Overall graft patency was 50%. Patency was documented in some specimens harvested at 200 days. The flap model is a good indicator of graft patency. PTFE grafts of 1.0-mm internal diameter are not yet equivalent to autologous veins. Future refinements, particularly aseptic technique, are expected to result in even higher patency rates.     

Clinical use of microvascular PTFE grafts

This paper reports on the first clinical case where a polytetrafluoroethylene (PTFE) graft of less than 3 mm in diameter was implanted in the arterial system of a patient to bridge a vascular defect. A 1.5 cm long, 1.5 mm diameter prosthesis was interposed in the superficial palmar arch of a man who sustained a laceration of the palm of his dominant hand. The graft was implanted by means of the 3M Precise Microvascular Anastomotic System on one end, and by conventional microsurgical technique on the other end. There were no postoperative complications. The patient resumed his preinjury activities 9 weeks after trauma. Serial Doppler ultrasound examinations showed normal blood flow and complete patency of the graft. An angiogram performed 12 weeks postoperatively confirmed the patency of the prosthesis. Twelve months post-operatively the patient is free from complications. The use of small diameter PTFE prostheses may be considered when planning grafting procedures for microvascular defects. © 1995 Wiley-Liss, Inc.     

The air test as a clinically useful indicator of intravenously placed epidural catheters

The authors performed a clinical trial in 313 patients in labor to determine the safety and efficacy of an air test for unintentional intravenous placement of epidural catheters. Following routine aspiration for blood and cerebrospinal fluid, 1 ml of air was injected through each epidural catheter while heart tones were continually monitored with a Doppler ultrasound probe placed over the maternal precordium. In 281 patients, Doppler heart tones did not change following air injection (negative air test). All but eight of these patients developed an adequate level of analgesia following anesthetic administration, and no patients with negative air tests developed signs or symptoms of local anesthetic toxicity (false-negative rate, 0%; 95% confidence limits, 0.0-1.1%). Doppler heart tone changes followed air injection in 22 cases (positive air test). In 16 of these, intravenous catheter position was subsequently shown by aspiration of blood from the catheter or by the use of test doses consisting of local anesthetics with or without epinephrine. In six cases, adequate levels of analgesia developed despite a positive air test (false-positive rate, 2%; 95% confidence limit, 0.7-4.3%). None of the 303 patients receiving the air test developed any complications attributable to the injection of air (95% confidence limits, 0.0-1.0%). The authors conclude that air, with precordial Doppler detection, is a safe and effective test for identifying intravenously located epidural catheters.     

Use of stretch expanded polytetrafluoroethylene as a microvascular graft in a low-pressure situation

OBJECTIVE: Microvascular reconstruction is often limited by the availability and length of the pedicle. The harvesting of autologous vein grafts adds morbidity and may not provide a good match. Expanded polytetrafluoroethylene (ePTFE) grafts have been used routinely in macrovascular surgery. However, there are no conclusive data on the performance of small-diameter PTFE grafts for pedicle lengthening in free flaps in a low-pressure situation. In this study, we evaluated the efficacy of 3-mm diameter stretch ePTFE grafts to lengthen the venous pedicle of a free flap. METHODS: Fifteen male New Zealand white rabbits were operated on under sterile conditions. Using an operating microscope, an epigastric flap was raised and the pedicle was exposed and dissected to its origin from the superficial femoral vessels. A segment of the vein of 1 cm to 3 cm was replaced with a stretch ePTFE graft. Microsurgical anastomoses were performed using 9-0 nylon sutures. Four weeks postoperatively, the flaps were raised again with the pedicles re-explored. The graft was then removed and examined histologically. RESULTS: All the grafts demonstrated immediate patency. There were no cases of flap loss on the control side at 4 weeks postoperatively. When re-explored, the patent ePTFE grafts appeared to be covered by connective tissue. Light microscopy showed neoendothelialization with fibrovascular in growth. CONCLUSION: From this study, we can conclude that 3-mm diameter stretch ePTFE grafts can be used successfully as an alternative to bridging autologous vein grafts in free-flap pedicles.