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Biomedical subjects

J Awad

Publications and source records attributed to J Awad.

At least 73 records · Page 4Linked to original sources
PubMed1984

[First contact between blood and the arterial prosthesis. Study of the retention of the blood elements].

In order to characterize the nature of the interaction between arterial prostheses and their initial contact with blood, we propose the use of an in vitro test using labelled platelets and fibrinogen to measure the amount of the thrombotic matrix that is entrapped by the wall of the graft. The results have been confirmed by scanning electron microscopy. Polyester prostheses, whose healing process depends on the reorganisation of the thrombotic matrix, retains considerably more blood cells than the polytetrafluoroethylene microporous prostheses or the treated biological devices, whose fate, following implantation, maintains almost complete passivity.

Biocompatible Materials↗
PubMed1982

HLA antigen associations in hypertrophic cardiomyopathy.

Histocompatibility antigen testing has been carried out in 20 unrelated normotensive English Caucasoids with hypertrophic cardiomyopathy and in 17 relatives, six of whom also had the disease. A strong association with the HLA-DRw6 antigen complex was found (P = 0.0036) but it was no longer significant after correction for the 52 antigens tested (P = 0.1701).

Adolescent↗
PubMed1980

Defibrinogenation as an alternative to heparinization in prolonged extracorporeal circulation.

Complications arising from difficulty controlled bleeding and thrombus formation during procedures which require extracorporeal circulation with heparin as anticoagulant motivate the search for better hemostasis and anticoagulant technology. An enzyme (Defibrase), having a specific interaction with fibrinopeptide A such as to cause fibrin depletion in a soluble form, has been proposed as an alternative to heparin. Defibrase, in contrast to heparin, does not affect blood platelet function. Heparin and Defibrase as anticoagulants were compared in 8 h perfusion studies using arterio-venous extracorporeal blood circuits in dogs; the circuitry included pumps, membrane oxygenators and filters serially. Thrombus formation, in the filters and the oxygenators as well as pathology of the perfused animal were investigated. The results suggest that defibrase-like enzymes have potential for enhanced control of hemorrhagic and thrombotic phenomena. Although impeded by a latency of several hours before the full anticoagulant properties are developed in vivo, it appears that enzymatically mediated defibrinogenation of blood may be a valuable alternative to heparinization in extracorporeal circulation procedures.

Animals↗
PubMed1980

In vitro performance assessment of tubular membrane oxygenators.

The definite advantage in oxygen transfer performance of staged (single, double and triple) tubular membrane oxygenators (TMO) is compared with reference to flat membrane oxygenators (Travenol or Landé Edwards). The overall construction of staged TMO with a blood mixing chamber is a very good way to destroy the blood boundary layer and modify the blood stagnant zone in the device. Four sizes of staged TMO were studied using the principle that gases dissolve in water in concentrations linearly proportional to the partial pressures of the gases when in equilibrium with the liquid. The experimental results show that the oxygen transfer rate and the corresponding overall oxygen mass transfer coefficient of staged TMO are increased by the same order as those of the reference membrane oxygenators. Furthermore the essential parameter analysis prove that oxygen transfer increases with the number of stages and decreases with the length of the blood tubular modules. The multistage design of TMO revealed an increase in the hydrodynamic resistance occurring in the apparatus. However the highest relative oxygen transfer efficiency suggests that better fluid distribution as well as better uniformity of oxygenation prevail in the staged devices.

Evaluation Studies as Topic↗
PubMed1978

Scanning electron microscope study on flat type membrane oxygenator after prolonged extracorporeal circulation.

Despite adequate anticoagulation, thrombi may develop onto any foreign surface subjected to circulating blood. Although the efficiency of membrane oxygenators can decrease, distal embolization can be more critical and dangerous. Scanning electron microscope observations carried out on the Travenol Modulung oxygenator used both on dogs and on patients for prolonged partial cardiopulmonary by-pass pointed out the following observations. Caution must be observed when translating the results from dogs to human beings. Heparin management can be delicate and critical. The problem of blood transfusion can be extremely important and must be extensively investigated.

Adult↗
PubMed1978

Endothelial lesions associated with vascular clamping--surface micropathology by scanning electron microscopy.

The endothelial cell pavement in normal blood vessels is very fragile. In cardiovascular surgery, the need for secure clamping of the aorta results in trauma which may be followed by thrombosis or occlusion. Various types of vascular clamps and other related devices offered commercially were clinically investigated in canine models and their effects on the vascular endothelium were ascertained with the aid of scanning electron microscopy. On the basis of these studies, the Fogarty silicone filled clamp appeared to be the least traumatic. However, further technical developments in this area are needed in order to obtain a completely atraumatic method of temporarily closing major blood vessels.

Animals↗
PubMed1978

Albuminated dacron protheses as improved blood vessel substitutes.

An improved vascular graft was achieved by treating knitted Dacron prostheses with cross-linked albumin. Eight segments, each six centimeters in length, were coated and implanted in the canine thoracic aorta for periods ranging from 24 hours to six months. The results were compared with the eight untreated grafts implanted for similar periods as control experiments. Albumin coating resulted in a faster healing : cells appeared earlier and collagen development was greater. The most beneficial effect of that treatment was the reduction in embolization, as shown by the considerable decrease in kidney damage.

Animals↗
PubMed1977

Stored blood microfiltration. Evaluation of micro-aggregate filter composed of polyurethane foam and nylon wool.

Aggregates of amorphous material which develop during storage of banked blood have been implicated as a cause of pulmonary micro-embolism in man following massive transfusion. Such pulmonary micro-embolism may be a causal factor in the development of post traumatic pulmonary insufficiency. At present several microaggregate filters for use in massive transfusion are commercially available, and on of these is the Fenwal filter. It is composed of a screen filter which removes microclots of 250 microns and higher, a layer of polyurethane foam and a layer of nylon wool. The resistance of this device is very acceptable and the filter may be used for several blood units, but its efficiency seems less than that of Dacron wool filter.

Blood Platelets↗
PubMed1977

Dacron as arterial prosthetic material: nature, properties, brands, fate and perspectives.

Dacron graft prostheses are routinely implanted to overcome impairment of arterial flow to distal tissues. Many different fabric configurations have been developped and evaluated. Unfortunately, after implantation the flow surface of any graft persists as a fibrinous lining. No human specimen has a commonly ingrown extension of tissue exceeding some millimeters in length. Full wall healing and endothelialization of arterial prosthesis is a goal that must be pursued intensively because it seems that the goal is attainable.

Animals↗
PubMed1976

A new approach to the management of familial hypercholesterolaemia: Removal of plasma-cholesterol based on the principle of affinity chromatography.

Reduction of plasma-cholesterol by the removal of low-density lipoproteins (L.D.L.) in an extracorporeal system is described as a possible approach in the treatment of familial hypercholesterolaemia. L.D.L. were removed from the blood by their interaction with heparin linked to agarose beads in the presence of calcium ions. Plasma-L.D.L. was markedly decreased in two patients with heterozygous familial hypercholesterolaemia. The technique is specific for the removal of L.D.L., as the concentration of high-density lipoproteins was not affected. The treatment was well tolerated by all three subjects (i.e., two hypercholesterolaemic patients and a normal volunteer), and there were no undesirable effects. Several haematological parameters, clinical-chemistry tests, including serum enzymes, and immunoelectrophoresis of plasma proteins were all unaffected by the treatment.

Calcium↗
PubMed1976

Blood compatibility of silicone rubber chemically coated with cross-linked albumin.

A new method is reported for chemically coating cross-linked albumin onto silicone rubber in an attempt to improve the blood compatibility of the material. Promising results were obtained in an evaluation using both vena cava and renal embolus antithrombogenicity tests ondogs. Coated silicone rubber rings induced much less renal emboli than uncoated ones after one week implantation.

Albumins↗
PubMed1976

Disposable filters for microaggregate removal from extracorporeal circulation.

A comparative study of three commercially available blood filters for use in extracorporeal circuits was made in dogs. All filters were efficient in removing infused microclots from the circulation, but all caused mild thrombocytopenia and two produced minimal hemolysis. In dogs infused with microclots, only those animals without blood filters in the infusing circuit showed evidence of pulmonary microembolism at autopsy. It was concluded that while the filters have minimal disadvantages, their potential in reducing microembolism in extracorporeal circuits far outweighs these disadvantages.

Animals↗
PubMed1975

[Blood microfiltration. Scanning electron microscopic study of the aggregates retained by a transfusion filter made of polyurethane foam].

Preliminary studies of the transfusion filter Bentley PF 127, a polyfilter type with a graded serie of diameters of microfenestration are reported. Dog blood has been used in all instances of the trial phase. Variations of the hematological factors as well as biochemical disparities have been examined and all deposits were assessed by means of scanning electron microscope. Amounts of deposits increased with the blood age. As far as banked dog blood develops less microaggregates during storage than human blood, the SEM pictures reported are a plea for banked blood microfiltration in any transfusion to human beings. The deposits which were trapped in the polyurethane foam, had previously passed through a screen filter with pore size slightly wider than the standard one (250 microns instead of 170 microns). Unfortunately the possibility of thrombus formation is serious as far as banked blood is rather fragile, and due to a slow flow rate, the time of blood contact with the filter is enough to allow thrombus development. However, the amounts of clots greatly increased with the age of the blood. The importance of filtration by adsorption was not very visible. The future of such a depth filter is questionable: should we prefer a transfusion screen filter with small pore size, the efficiently of which is determined by its pore size, and which traps the microaggregates by mechanical retention, or a depth filter which is supposed to retain the microaggregates regard less of the size but which could be very easily thrombus invaded and does not allow a suffisant blood flow rate for patients needing large amounts of blood in period of initial resuscitation? The debate is open but we should recognize that a screen filter with small pore size is widely used in the hospitals.

Animals↗