Life support systems : the journal of the European Society for Artificial Organs最新文献

A technique is described for an extracorporeal arteriovenous shunt in dogs which allows the testing of biomaterials in the shunt for several months in the same animal. The details of the preparation of the tubes and of the surgical technique are given. In contrast to other techniques, encircling ligatures are not placed around the cannulated blood vessels.

Eighty transplanted patients were randomized to receive either a new antithrombotic agent, defibrotide (group A), or dipyridamole (group B) in addition to immunosuppressive therapy, in order to evaluate the effectiveness of these drugs in preventing graft vascular damage. While the incidence of rejection and the occurrence of specific anti-HLA antibodies were similar in the two groups, the peak serum creatinine levels during rejection were significantly lower in patients treated with defibrotide (3.3 +/- 1.8 versus 5.6 +/- 2.4 mg/dl; P less than 0.01), 97.5 per cent of whom had a still-functioning graft after a mean follow-up period of 24 months, compared with 80.5 per cent of the patients treated with dipyridamole (P less than 0.05). Graft biopsy, carried out during rejection, showed less severe vascular lesions in patients from group A than in those from group B. Our results suggest that the prophylactic administration of defibrotide may play a role in improving the long-term results of renal transplantation.

Recent clinical information indicates that the aluminium level of patients' serum can rise while they are being treated with the Sorbsystem haemodialysis system. Further evidence suggests that the quality of aluminium removed from the dialysing fluid by the sorbent cartridge utilized in this equipment is time-dependent. Evaluation of the sorbent cartridges D-3160 and D-3260 has shown that ultimately aluminium is satisfactorily removed from the dialysing fluid. However, the time taken to achieve the safe condition of less than 30 micrograms/litre of aluminium is dependent on the quantity of aluminium washed out from a new cartridge before being reabsorbed, and the highly variable quantity contained in the diluting water. The results have also shown that the level of aluminium recommended by the DHSS in April 1982 (30 micrograms/litre) is not reliably attained following the manufacturer's recommended pretreatment, and a further 60 min of operation in the 'dialyse' mode is necessary. It should be noted that, as a result of evaluation of the Sorbsystem, the DHSS have issued guidelines on the use of this equipment.

Haemodialysis was performed using heparin (dialysis I: heparin regimen 1, 2000 U/h) in ten patients. These subjects were then given an infusion of prostacyclin, in the form of epoprostenol sodium salt (dialysis II: prostacyclin, 5 ng X kg-1 X min-1), followed by an infusion of prostacyclin and heparin (dialysis III: heparin regimen 2,500 U/h). Absolute platelet count, in vitro platelet aggregation and plasma beta-thromboglobulin decreased during prostacyclin infusion. Haemodialysis neutropenia was improved by prostacyclin. The membrane sieving coefficient factor and ultrafiltration volume were not improved by prostacyclin alone (dialysis II). Prostacyclin together with heparin (dialysis III) showed, 60 minutes after the start, an unchanged sieving coefficient factor compared with that of heparin alone, while the ultrafiltration volume significantly (P less than 0.001) improved. The results of this study confirm those of earlier studies and suggest that prostaglandin I2 together with low-dose heparin improve the biocompatibility and efficiency of dialysis treatment.

The hydrogen bubble technique was used to visualize flow past two different aortic valve prostheses. The results reported in this paper clearly show the efficacy of the method and its main advantage, namely that tracers can be produced at any position and at a completely controlled rate. This fact allows the study of either selected moments or regions of the flow field, thus enhancing contrast and therefore increasing the signal-to-noise ratio of the picture. The possible perturbations introduced by the cathode may be decreased to a minimum by using small-diameter wires or wall flush-mounted thin plates. On the other hand, the buoyant velocity of the bubbles may be only a few percent of the fluid velocity and therefore not substantially affect the results. Within the limited scope of the present investigation, the xenographic valve seems to disturb the flow significantly less than the Björk-Shiley prosthesis, both for steady and pulsatile flow, as shown by the traverse velocity profiles or through turbulent stress mapping.

A computer model simulating the electrical activity of the heart is described. The model is designed for use in clinical cardiological research. Its implementation is based on the methods of discrete process simulation. The simulation program is written in FORTRAN, has approximately 12,000 lines and requires 160 kilobytes of memory to run. The whole heart is modelled, including a realistic description of the conduction system and a 'hollow shell' structure with a central plane representing the atrial, ventricular and septal components of the cardiac musculature. The myocardium itself is represented by simple hexagonal elements, which are pieced together to form the 'hollow shell'. The ideas used to develop the model are briefly described, but emphasis is given to clinical applications. The model is first validated by examining its output under well-known pathological conditions. Clinical applications, including predictive value, testing of hypotheses, and evaluation of pacemaker function, are then described, results being presented in the form of orthogonal lead projections.