Scanning Electron Microscopy Analysis of Polyethylene Oxide Hydrogels for Blood Contact

Hydrogels are a class of synthetic material, composed of a polymer-water matrix and have been proposed as tissue substitutes and drug delivery vehicles. Polyethylene oxide (PEO) hydrogels were synthesized and used to produce coated wires and conduits for baboon blood compatibility studies. Blood-material interactions were studied both by Scanning Electron Microscopy (SEM) and 111In labeled platelet deposition. SEM processing modifications were first evaluated in order to reduce shrinkage and surface distortion incurred during sample preparation of these high water content materials. Pretreatment with 1% tannic acid reduced bulk shrinkage associated with critical point drying by 10-20%. This effect is small, nevertheless, it prevented major sample disruption. Coated guidewires were exposed to baboon blood for one hour in the inferior vena cava and conduits were placed for either 30 or 60 minutes in an ex vivo femoral arteriovenous shunt. Reference materials included Gore-tex®, polyethylene and silica-free polydimethyl siloxane (PDMS). In the guidewire studies, 111In labeled platelet levels were highest on Gore-tex® (6568.97 platelets/ 1000 μm2) and large thrombotic deposits were well visualized by SEM. Formulations containing PEO had low levels of platelet deposition and little evidence of platelet activation was noted by SEM. Shunt studies demonstrated that materials of high PEO content and molecular weight had the lowest levels of platelet deposition. After 60 minutes of blood flow, mean platelet deposition on PDMS and Gore-tex® was 50 and 1000 fold higher than on a network composed of 65% PEO 20,000 (p \u3c 0.05). SEM confirmed these findings

Analysis of arterial intimal hyperplasia: review and hypothesis

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Despite a prodigious investment of funds, we cannot treat or prevent arteriosclerosis and restenosis, particularly its major pathology, arterial intimal hyperplasia. A cornerstone question lies behind all approaches to the disease: what causes the pathology? Hypothesis: I argue that the question itself is misplaced because it implies that intimal hyperplasia is a novel pathological phenomenon caused by new mechanisms. A simple inquiry into arterial morphology shows the opposite is true. The normal multi-layer cellular organization of the tunica intima is identical to that of diseased hyperplasia; it is the standard arterial system design in all placentals at least as large as rabbits, including humans. Formed initially as one-layer endothelium lining, this phenotype can either be maintained or differentiate into a normal multi-layer cellular lining, so striking in its resemblance to diseased hyperplasia that we have to name it "benign intimal hyperplasia". However, normal or "benign " intimal hyperplasia, although microscopically identical to pathology, is a controllable phenotype that rarely compromises blood supply. It is remarkable that each human heart has coronary arteries in which a single-layer endothelium differentiates earl

Below-Knee Amputation: Is the Effort to Preserve the Knee Joint Justified?

• The records of 50 patients (31 men and 19 women, ranging in age from 49 to 89 years) undergoing definitive below-knee amputation for ischemia from May 1971 to May 1979 were reviewed. Forty-three (86%) had ulceration or necrosis involving the foot or toes. Seven had rest pain without tissue loss. Overall healing rate was 86%. Seven patients (14%) failed to heal and required reamputation above the knee; the functional status of the remaining 43 patients was graded preoperatively and at the time of late follow-up (mean, 3.4 years). Twenty-five of 35 (71%) unilateral below-knee amputees could walk with a prosthesis; ten could not. Seventeen patients (34%) either required an additional, higher amputation or did not use the knee joint to increase mobility. The patient with marginal circulation and marked preoperative functional limitations may have the above-knee level as the chosen site for amputation.(Arch Surg 115:1184-1187, 1980