Biomedical subjects
Publications and source records attributed to P Bonnaud.
Using 9 personal surveys and 11 cases found in the literature, the authors analyse the etiologies of this iatrogenic accident, the often secondary modalities of the diagnosis and the benign nature of the fistula which usually heals spontaneously.
From 1972 to 1992, 790 vascular conduits were implanted as vascular access in hemodialysis patients, of whom 402 were "longs" (length above 15 cm), with 168 PTFE grafts and 234 homosaphenous preserved vein grafts matching 136 manufactured and 98 self-prepared grafts. Functional period of time as 10 years has been obtained with the two materials, and up to twelve years with one manufactured graft. Among complications were observed 12% serious infection with PTFE graft compared to 2% with homosaphenous graft; aneurysm on 9% of PTFE grafts and 11% of saphenous graft, stenosis on vein graft anastomosis in 65% of the PTFE cases and 85% of the saphenous cases. There were 12% complications specific to PTFE grafts. Finally, homosaphenous vein is a material of choice in hemodialysis vascular access, mainly with the manufactured grafts.
The Carboclip is a no-needle vascular access device made of an inverted Titanium body. The horizontal bar of 6 mm inner diameter is connected with artery and vein via a vascular graft. The vertical body houses an elastic plug in which is inserted a double canula diving in the blood stream for extracorporeal blood circulation (EBC). The body is wrapped by a flange made of microporous biocarbon in which the subcutaneous fibroblast will growth, forming an antimicrobial barrier and fixing the port to the skin. We report our experience on 30 devices implanted in 30 sheep with 26 extracorporeal circulation simulating hemodialysis. The results demonstrate good tightness of the plug as well at rest as during EBC procedure, sufficient blood flow rate of about 400 ml/min, and benefits of the microporous carbon flange.
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The popularity of expanded polytetrafluoroethylene (PTFE) arteriovenous fistulas for hemodialysis access is increasing. The low infection rate, low thrombogenicity and low body reactivity make it an important blood access for patients on routine hemodialysis. The authors examined 29 PTFE graft fistulas surgically excised from patients on hemodialysis for one or more of the following complications: infection 7, 2 with associated hemorrhage; thrombosis 9; aneurysm 11, 3 with associated thrombosis; stenosis 5, 3 with associated thrombosis; hemorrhage 4 and arterial steal 2. The explanted prostheses were reinforced Gore-tex in 20, Gore-tex thin wall in 1, Impra I in 4, Impra II in 3 and Vitagraft in 1. It was also noted that the implants failed in the short term mainly because of infection, in the medium term mainly because of thrombosis and stenosis, and in the long term usually because of aneurysm.
The suitability of stripping vein homografts as AV fistulae for intermittent hemodialysis has been evaluated. Microscopic investigation of stored veins indicated the superiority of cryopreservation over refrigeration. A systematic study of 12 venous homograft fistulae surgically excised from hemodialysis patients revealed that the homograft walls are the sites of both connective tissue proliferation and of mural degeneration. It was also noted that the implants failed in the short term (less than 1 yr) mainly due to stenosis, in the medium term (1 yr-3 yrs) mainly due to aneurysmal dilatation and for a variety of reasons beyond 3 years. It was concluded that when suitably selected, handled and stored, stripping vein homografts are a viable alternative to treated human umbilical or bovine heterografts as blood access fistulae if no autograft is available.
Three bovine carotid heterografts, used for vascular access, were analysed after removal following the development of aneurysms in two cases and thrombosis in one. The first prosthesis was implanted in a 17-year-old man who suffered from myasthenia gravis and was undergoing plasmapheresis. It became notably dilated several months after implantation, and resection was necessary 14 months after insertion. The second graft was placed in a 31-year-old woman being treated for a severe chronic potassium insufficiency. It was removed 16 months after insertion because of thrombosis. The third bovine carotid heterograft was inserted in a 48-year-old patient on long-term hemodialysis and was removed 3.5 months later because of aneurysmal dilatation adjacent to the arterial anastomosis. These evolutionary and degenerative changes associated with the bovine carotid heterograft illustrate the limitations of this material as an interpositional limb for arteriovenous fistulas in angioaccess therapy. Small weaknesses have sometimes been noted in the microstructure of the graft material studied before implantation.
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When the renal pelvis and the proximal ureter are destroyed, surgical repair is always difficult. In case of a loss of substance of the upper ureter, it is possible to replace the obstructed (or destroyed) segment and to preserve the healthy iliopelvic ureter. The 'renoureteric bypass' consists of the insertion of an intermediate segment between the lower calyx of the kidney and the lumboiliac ureter. A prosthesis or an intestinal loop may be used to restore the continuity of the urinary tract. The results obtained in dogs being excellent, the technique was applied successfully in man in 2 cases.
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Segmental replacement of the ureter using an intestinal segment has given good long term experimental results. Preservation of the pelvic ureter has two advantages:--The use of a short intestinal loop, which decreases the secretion of mucus, stagnation and electrolyte reabsorption;--preservation of the normal uretero-vesical junction, thereby avoiding reflux. At the beginning of this experimental study, it was feared that the pelvic ureter would become obstructed by mucus and that the insufficiently contractile and atonic ileal loop would dilate, forming a "pool" of stagnant urine. In fact, no such complications were seen.
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