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

Glutaraldehyde stabilizes pericardial tissue in prosthetic heart valves by forming covalent cross-links between collagen molecules. If the cross-linking is nonuniform owing to variable penetration of the glutaraldehyde, areas of the tissue may become sites for enzymatic attack or become potentially antigenic. Cross-linking can be easily assessed by measuring the shrinkage (thermal denaturation) temperature of the tissue. We used differential scanning calorimetry to perform a stratigraphic analysis of the shrinkage temperature of glutaraldehyde-treated pericardium. In the fixation conditions used (0.25 per cent glutaraldehyde for 28, seven and two days and for 2 hours), no variation was found in the shrinkage temperature measurement throughout the thickness of the tissue. This indicates uniform penetration of fixative and cross-linking throughout the tissue.

This study discusses the surgical aspects of permanent cardiac pacemakers with reference to a ten-year review involving 628 procedures. The most suitable route for electrode placement was found to be subclavian vein puncture, access being achieved in 97% of cases. This method was however, associated with a small incidence of pneumothorax (1.4%) and haemothorax (0.9%). The commonest late complication is infection in spite of sterile technique and antibiotic prophylaxis. Experience with infected pacemakers suggest that the best line of management is complete removal of the system followed by delayed replacement once the infection has been eradicated. Pacemaker technology is constantly improving, providing both patient and physician with increasingly elaborate tools. In order to reap the benefit of these pacemakers, the data from this review demonstrates the need for meticulous technique in their insertion and an ability to deal with any complication promptly and adequately.

Prognostic factors of Low Output Syndrome (LOS) requiring operative circulatory support by intra-aortic balloon-pumping (IABP) counterpulsation, were analysed in a population of 841 patients who underwent heart valve replacement surgery between June 1977 and May 1985. The incidence of IABP circulatory support was 6.8%. Mean survival time of patients who needed IABP was 2.35 years +/- 0.425 vs 6.30 years +/- 0.103 for patients who didn't have this complication. A multivariate analysis using the logistic model was done to pinpoint factors predictive of IABP support. The prognostic factors were pre-operative functional class, presence of prior valve replacement, presence of concomitant surgery and presence of endocarditic etiology. The subgroup of 58 patients undergoing balloon counterpulsation was analysed for factors predictive of survival using a multivariate analysis of the Cox' model. Presence of aortic or mitral regurgitation was found to be the independent risk factor of mortality. Using a combination of prognostic factors, we pinpointed groups of patients at high risk of needing post-operative balloon pump counterpulsation support. The necessity of an alternative procedure for the mechanical support of the failing circulation is underlined.

It has been demonstrated in our laboratory that blood flow pulsations enhance plasma filtration rate by 30-60 per cent. The increase in plasmafiltration over the steady flow value is found to be a function of the parameter F. delta V'/QB where F denotes the pulsation frequency, delta V' the volume amplitude of pulsed blood in the filter and QB is the time mean blood flow. The increment in plasma filtration may be related to the increase in time-mean absolute value of shear rate.

The combination of an ultrafiltration device with an exchanger whose semipermeable hollow fibres are covered with renal epithelial cells is proposed as a design for a bioartificial kidney. We first demonstrated that continuous ultrafiltration can be maintained for relatively long periods in the absence of anticoagulation. As a second step, we report here the feasibility of attaching and growing two lines of kidney epithelial cells (MDCK and LLC-PK1) on two different semipermeable materials, an acrylic copolymer and a polysulphone. Cells seeded on acrylic copolymer hollow fibres reach confluence within three weeks. Depending on the chemical and/or physical properties of the polymer, the cells show distinct differentiated morphology, which may influence their ability to perform specialized tasks.

To facilitate patients' movement, we developed a simplified portable haemodialysis system, using a sorbent cartridge (Organon Teknika) for regeneration of the dialysate. The whole system is in two parts: (1) a compact disposable container for dialysate recirculation with dialyser and blood and dialysate lines; (2) a dual functions circulatory assistance monitor. The pack system is easy to use: single-use; no water processing; no formalin processing; reliable for temporary use (because of its aluminium), providing excellent purification; compact and portable, it permits greater freedom for the patient, and with adequate dialysis.

Drug delivery by controlled-release devices is used extensively in clinical practice and laboratory experiments. There are many external and implantable pumps available, but their cost is high and modification, when desired, to suit any special requirement is often difficult. We have tested a plastic infusion device fabricated from materials readily available in our research laboratory. The infusion device consists of a collapsible solution reservoir protected by a double jacket with vents to prevent the permeation of the volatile propellant contained in a rigid external casing. The flow moderator is a hollow glass-fibre, and flow rates as low as 100 microliter/h or less were maintained for an extended period without becoming occluded. In vivo tests on Wistar rats using a heparin solution demonstrate that controlled release of the anticoagulant was achieved, as indicated by the delay in the normal Lee-White clotting time. Since its size, service life and flow rate may be selected to suit the infusion requirement in an experiment, the device should be readily adaptable for the delivery of other drugs.