Significant reduction in circuit pressure with modified plasma separation chamber for a heparin removal device

The heparin removal device (HRD), using plasma separation and poly-L-lysine (PLL) affinity adsorption, has been shown to be an effective alternative to protamine after cardiopulmonary bypass (CPB). Previous designs of the HRD used standard Luer-Lok ((phi = 2.3 mm) port connections between the extracorporeal tubing and the plasma separation chambers, which resulted in excessively high circuit pressures (> 750 mm Hg) at an HRD flow of 1,400 ml/min. To reduce circuit pressures, we enlarged the connection ports to phi = 4.2 mm, keeping other circuit components and sorbent amounts unchanged. The modified circuit HRD was divided into the SMALL PORT group (phi = 2.3 mm, A = 4.15 mm2) and the LARGE PORT group (phi = 4.2 mm, A = 13.85 mm2) in adult swine (70+/-5 kg) given 300 U/kg heparin. A dual lumen cannula was inserted into the right atrium and connected to the HRD. Inlet pressure ranged from 749+/-42 to 795+/-57 mm Hg in the SMALL PORT group during the HRD run at 1,400 ml/min, whereas it ranged from 345+/-5 to 372+/-34 mm Hg in the LARGE PORT group (p < 0.01 between groups). Likewise, the chamber pressure ranged from 447+/-21 to 452+/-27 mm Hg in the SMALL PORT group and from 190+/-14 to 204+/-19 mm Hg in the LARGE PORT group (p < 0.01 between groups). There were no significant differences in ACT between groups. We conclude that enlarged chamber ports significantly lower circuit pressures for the HRD without changing heparin removal capability.