Processes human umbilical veins as arterial substitutes--evaluation in canine models.

Human umbilical cord vein segments have been used as vessel substitutes for damaged or occluded arteries, as aorto-coronary by-passes and as arterio-venous fistulae for dialysis. The Dardik-Biograft fixed with glutaraldehyde and the Mindich-Bioflow, fixed with ethanol and dialdehyde starch, are commercially available. They were implanted in dogs as replacements for a segment of the abdominal aorta. Post-implantation status was followed by angiography. They were evaluated after removal from sacrificed animals with the aid of scanning electron microscopy and histological techniques. Attention was focused on vessel patency, dimensional stability, integrity of the anastomosis line, lumen wall microstructure, evidence of suture damage and thrombus deposition pattern. Both types of grafts gave functional by-passes for at least until 6 months post-implantation. The Dardik-Biograft appeared more prone to thrombus formation near the anastomosis. Sparse cellular development was also noted. The Mindich-Bioflow gave rise to a prosthesis of superior thromboresistance which was more subject to mechanical damage.

[Urokinase (in situ) in the case of acute ischemia of the lower limbs (author's transl)]. / L'urokinase in situ dans l'ischémie aiguë des membres inférieurs.

Eighteen patients with severe, acute ischemia of the lower limbs were treated with an arterial perfusion of the ischemic leg with Urokinase. This was associated, in thirteen patients, with a limited attempt of revascularization. The result of this treatment was an immediate improvement in twelve cases, which lasted, more than six months, in six patients. The authors insist on the interest of the arteriography performed after the fibrinolytic treatment in order to complete the revascularization.

[Progressive complications associated with polyester arterial prostheses. Study of 61 specimens following surgical excision]. / Complications évolutives associées aux prothèses artérielles en polyester. Etude de 61 spécimens après exérèse chirurgicale.

Reports of individual surgical cases tend to be anecdotal because of the unique circumstances surrounding the patient, the surgeon, the intervention and, where applicable, the prosthetic device. To overcome this limitation the authors have taken a wider collaborative approach and report the analysis of 61 explanted polyester arterial prostheses associated with delayed complications on 53 patients reoperated upon in six different French hospitals. One advantage of such an independent and centralized retrieval programme is that the impact of centre specific factors, such as patient selection and surgical techniques, is minimized. Consequently, by following a standardized protocol for the evaluation of the morphologic, pathologic and mineralogic characteristics of the tissue surrounding the excised grafts, as well as the textile structure of the prostheses themselves, it has been possible to distinguish between iatrogenic and disease related complications and to demonstrate a number of general findings associated with the clinical performance of polyester arterial prostheses. Complications such as thromboses, infections and false aneurysms appear to occur randomly after different lengths of implantation, thicker fibrous tissue capsules are associated with velour grafts with highly textured yarns, the incidence of mineralized tissue and of endothelialized luminal surfaces is rare, weft knitted textile prostheses appear less mechanically stable and more sensitive to iatrogenic trauma than warp knitted, and the incidences of lipid and cholesterol adsorption, bacterial colonization and sterile fluid loss need further investigation. These observations lead to the recommendation that for patients with longer life expectancies surgeons should consider selecting low porosity, woven or warped knitted prostheses which contain yarns that have not been highly textured.

[Effects of Tham, isoprenaline and propranolol on the blood flow and vascular resistance of the liver after clamping of the afferent and efferent vessels. Relation to splanchnic shock]. / Effets du Tham, de l'isoprénaline et du Propranolol sur le débit et les résistances du foie après clampage des vaisseaux afférents et efférents. Relations avec le choc splanchnique

To determine the roles of portal circulation and the hepatic arteries during states of shock, the authors studied on 38 dogs, the effects of 30 minutes clamping of the sub-diaphragmatic part of the inferior vena cava, the portal vein and the hepatic artery, either together or successively. They measured the pressure in these various vessels, the transhepatic flow, using Xenon133, and calculated the intra-hepatic resistance. The animals were then treated with Tham, isoprenaline and propanolol. Tolerance to clamping was improved significantly when the animals were treated with the association of these drugs. The portal pressure and the systemic arterial pressure, rapidly returned to normal. This was also the case with hepatic, venous or arterial blood flow. There was a remarkable stability between the sinusoidal and biliary resistances, compared with disturbances in control groups. The already well known beneficial effect of Tham was increased by the apparently paradoxical association of isoprenaline and propranolol. In fact, with this dosage, they counter-balanced their reciprocal disadvantages. Finally, a study of blood flow and vascular resistance in the liver, suggests the existence of two components in splanchnic shock, hepatic and visceral.

[Glutaraldehyde - fixed human umbilical cord vein as a small diameter arterial substitute. Experimentation on the monkey]. / La veine ombilicale humaine traitée au glutaraldéhyde comme substitut artériel de petit diamètre. Expërimentation sur le singe.

Autologous saphenous veins, the preferred substitute material for aorto-coronary, femoro-popliteal and femoro-tibial by-pass, are usable in only 70% of individuals in need of such procedures. The development of small diameter substitute arteries is therefore essential to broaden the pool of patients who could benefit from this class of cardiovascular surgery. Existing substitutes, however, present major difficulties and have had limited success. In this laboratory, an attempt has been made to develop a vessel of 3 millimetres or less in diameter derived from human umbilical cord processed in glutaraldehyde. This substitute can be stored in 45% ethanol or dessicated by critical point drying. This device had been implanted as a segment of abdominal aorta in eight primates (Macaca fascicularis). Preliminary results are disappointing. The indicate that retention of a patency for more than a year post-implantation is difficultly achievable and that connective tissue hyperplasia leading to occlusion at the anastomoses is a major problem. Similar but larger diameter by-passes in the order of 6-8 millimetres should be investigated in greater detail, in order to better establish the "in-vivo" behavior of this class of tissue prosthesis. This would address the more fundamental issues pertaining to the clinical usefulness of fixed biological tissue by-pass devices.