Ex vivo evaluation of a Taylor-Couette flow, immobilized heparinase I device for clinical application

Abstract

Efficient and safe heparin anticoagulation has remained a problem for continuous renal replacement therapies and intermittent hemodialysis for patients with acute renal failure. To make heparin therapy safer for the patient with acute renal failure at high risk of bleeding, we have proposed regional heparinization of the circuit via an immobilized heparinase I filter. This study tested a device based on Taylor-Couette f low and simultaneous separation͞ reaction for efficacy and safety of heparin removal in a sheep model. Heparinase I was immobilized onto agarose beads via cyanogen bromide activation. The device, referred to as a vortex f low plasmapheretic reactor, consisted of two concentric cylinders, a priming volume of 45 ml, a microporous membrane for plasma separation, and an outer compartment where the immobilized heparinase I was f luidized separately from the blood cells. Manual white cell and platelet counts, hematocrit, total protein, and fibrinogen assays were performed. Heparin levels were indirectly measured via wholeblood recalcification times (WBRTs). The vortex f low plasmapheretic reactor maintained significantly higher heparin levels in the extracorporeal circuit than in the sheep (device inlet WBRTs were 1.5 times the device outlet WBRTs) with no hemolysis. The reactor treatment did not effect any physiologically significant changes in complete blood cell counts, platelets, and protein levels for up to 2 hr of operation. Furthermore, gross necropsy and histopathology did not show any significant abnormalities in the kidney, liver, heart, brain, and spleen.

Cleavage of the antithrombin III binding site in heparin by heparinases and its implication in the generation of low molecular weight heparin

“…Thus, the use of heparinase I or II for the generation of LMWHs requires extreme caution to ensure retaining intact AT-III sites in LMWH fragments. In fact, the results demonstrated herein show that heparinases I or II may be ideal agents for the neutralization of pharmacological doses of heparin (20)(21)(22).…”

Sex and flow: the consequences of fluid shear for sperm–egg interactions

“…Fluid-dynamics research provides excellent theoretical and empirical tools for examining the relationships between laminar-shear flow and cell behavior (Adler, 1981;Konstantopoulos et al, 1998;Chen et al, 2004). Specialized flow chambers, such as the Taylor-Couette apparatus (Bartok and Mason, 1957;Goldsmith and Marlow, 1972;Karp-Boss and Jumars, 1998;Ameer et al, 1999), cone-and-plate viscometer (Highgate and Whorlow, 1970;Solomon and Boger, 1998) and many types of microfabricated devices (Dellimore, 1976;Meng et al, 2005), have enabled studies of flow and particle interactions. Several results have shown that flow dominates behavior and cells are transported like passive particles (Rossman, 1937;Happel and Brenner, 1965;Shimeta et al, 1995;Karp-Boss et al, 2000;Dombrowski et al, 2004).…”

Delivery of therapeutic levels of heparin and low-molecular-weight heparin through a pulmonary route

“…Activity Assays. Whole-blood recalcification times were used to indirectly determine the amount of heparin present in the blood, as described (16). In most cases with LMWH, anti-Xa activity was used as a surrogate marker to monitor plasma drug levels.…”

“…were directly measured by using a modification of published procedures (16). Initial experiments were predicated on the concept that significant absorption of heparin into the bloodstream required efficient delivery of heparin to the deep lung, where particles or droplets of heparin could effectively cross the alveoliblood barrier.…”