Biomedical subjects

U Baurmeister

Publications and source records attributed to U Baurmeister.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Modified cellulosic dialyzer membranes: an investigative tool in thrombogenicity studies.

We have previously demonstrated that chemical modification of cellulosic membranes with dimethyl-amino-ethyl (DEAE) groups significantly improves membrane properties in terms of biocompatibility. Here, we show that DEAE substitution also alters the membrane's thrombogenic properties, and cellulosic membranes with various amounts of DEAE substitution were produced. Clinical dialyzers were constructed using two experimental membrane materials: modified cellulose-low (MC-low) and MC-high; standard unsubstituted cellulose was used as a control. Six patients were treated for a period of 3 weeks with each type of dialyzer and a heparin dose of less than 6000 IU/treatment. MC-low exhibited less extracorporeal beta-thromboglobulin and thromboxane B2 release than MC-high or Cuprophan. In addition, residual blood volume after clinical use was lower in the MC-low type. MC-low and MC-high induced less complement activation than Cuprophan, as characterized by extracorporeal C5a and C3a plasma concentrations (75% less C5a generation and 50 to 70% less C3a generation than unsubstituted cellulose).

Cellulose↗

PubMedDate not supplied

Backfiltration: does it occur in membrane plasma separation?

Backfiltration in hemodialysis refers to local filtration of dialysate into the blood compartment. This investigation was performed to examine whether there is a similar backfiltration phenomenon in membrane plasma separation. It was shown experimentally in hollow fiber devices that there is a flow of plasma through the filtrate side parallel to the blood flow inside the fiber. This bypass flow includes a backfiltration of the plasma from filtrate to the blood compartment near the end of the module. The following experimental results show the existence of bypass flow and backfiltration. In the case of no net filtration, these findings were made: 1) the existence of an offset of mean transmembrane pressure and 2) the blood side pressure drop in ACD-blood was less in impermeable fibers than in permeable ones. Filtrate pressure is higher than module outlet pressure at a wide range of filtration rates. In summary, backfiltration is not restricted to zero net filtration but occurs under the conditions of clinical use. Therefore, backfiltration is a crucial issue for device safety, because any contamination or wash-out from the membrane can reach the blood side.

Equipment Safety↗

PubMedDate not supplied

Successful long-term use of a miniaturized plasmapheresis circuit in rabbits.

Dual lumen silicon rubber right atrial catheters were implanted into the jugular of 8 rabbits and tunneled subcutaneously to exit sites between the ears. Using a miniaturized tubing-pump system, blood flow rates of 25 ml/min could be achieved for up to 3 1/2 hours without sign of hemolysis in an extracorporeal blood circuit. Seven catheters functioned an average of 75 +/- SE 19 days (range 24-117). One catheter remains functional after 176 days. Infection and thrombosis were the main reasons for failure. 20 plasmaphoresis experiments were carried out in four heparinized rabbits (blood flow rates 15 ml/min, plasmaflux 1.5-2.0 ml/min) using polypropylene minifilters (average pore size, 0.55 micron) with the plasma recirculated back into the animal. No hemolysis was detectable throughout the 4 hr experiment. Plasma proteins with a MW of 69 X 10(3) to 3 X 10(6) (Albumin, LDH, SGOT, SGPT, CPK, fibrinogen, LDL) showed a sieving coefficient close to 1.0. The good filtration performance and the absence of side effects make this system a possible use for plasmaphoresis in neonates.

Animals↗