Blood oxygenators heparin

PDMS-co-PS has been proposed to have the antithrombogenicity. PDMS-PEO-heparin has been synthesized to achieve better blood compatibility. Silicone-PC copolymers are always used as blood oxygenation, dialysis, and microelectrode membranes. 

Recently developed blood oxygenators are disposable, used only once, and can be presterilized and coated with anticoagulant (e.g., heparin) when they are constructed. Normally, membranes with high gas permeabilities, such as silicone rubber membranes, are used. In the case of microporous membranes, which are also used widely, the membrane materials themselves are not gas permeable, but gas-liquid interfaces are formed in the pores of the membrane. The blood does not leak from the pores for at least several hours, due to its surface tension. Composite membranes consisting of microporous polypropylene and silicone rubber have also been developed. 

Organic samples are usually mineralized to render them soluble in water and to eliminate possible interference from the matrix (for example through adsorption on the electrode surface). Mineralization can be carried out by heating with strong oxidizing acids, by fusion with alkalis or by combustion in an oxygen atmosphere [142]. Blood samples must be treated with heparin if they are not immediately analysed and the content of O2 and CO2 must be carefully maintained otherwise the dissociation equiUbrium of calcium is shifted [78,96]. 

In the previous papers(12,13), we reported on the vessel access type, i.e. tubular type, glucose sensor. It consisted of a glucose electrode system with a GOX enzyme immobilized Nylon membrane and a glucose semipermeable membrane, and a reference oxygen electrode system. The sensor could directly measure up to 700 mg/dl of BGL in an arterial blood stream when it was placed into an external A-V shunt. This sensor, however, has some problems such as thrombus during in vivo testing without heparin and clinical complexity associated with implanting the sensor in a blood stream. 

Fibrinogen Biosynthesis by Isolated Liver. In our isolated rat liver perfusion studies homologous heparinized oxygenated rat blood is routinely diluted with Ringer s solution, so that its final volume is in-... 

The intestine is isolated and perfused via the mesenteric artery with oxygenated perfusate, preferably, heparinized blood at 37°C and at a physiological pressure and blood flow. Venous blood from the portal vein is either collected first pass or returned to the reservoir for reoxygenation and recirculation. The effect of bile on absorption from the gut can be assessed by the infusion of bile via an indwelling cannula that is inserted into the bile duct in the direction of the gut. 

Fresh normal heparinized blood (25 ml) was hemolyzed with 3 ml 7% Sterox SE solution 10 ml of the hemolysate was rotated for 3 minutes in a small tonometer filled with oxygen to procure a solution containing 100% Hb02 (Z) V-D = 0.609). The Hi content of this solution was estimated to be near zero with the method described in Section 7.3. This solution was designated A. Another 10 ml of the hemolysate was rotated for 5 minutes in a small tonometer with pure CO to procure a solution containing 100% HbCO (D yZ) = 0.915). This solution was designated B. 

Extracorporeal medical machines (e.g., artificial kidney, pump-oxygenator) perfused with blood have been an effective part of the therapeutic armamentarium for many years. These devices all rely on systemic heparinization to provide blood compatibility. Despite continuous efforts to improve anticoagulation techniques, many patients still develop coagulation abnormalities with the use of these devices (1-3). Even longer perfusion times may occur with machines such as the membrane oxygenator. In such cases, the drawbacks of systemic heparinization are multiplied (4). A number of ap-... 

Figure 1. Proposed heparin circuit. The extracorporeal device could be a renal dialysis unit or a pump-oxygenator. The heparinase reactor could be part of a blood filter to be used either continuously (in which case heparin would, be added, continuously at the start of the circuit) or at the end of an operation. Heparin could thus be confined to the extracorporeal circuit.

At present, synthetic blood filters are routinely placed at the effluent of extracorporeal devices such as the pump-oxygenator or artificial kidney to remove clots or aggregates formed during the perfusion. The filters used in oxygenators can be as large as 2 L, whereas those used in renal dialysis are only several milliliters. With further development, heparinase could be immobilized to polymers in these filters. In this case, the filter could remove both clots and heparin. 

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