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 t o protamine after cardiopulmonary bypass (CPB). Previous designs of the HRD used standard Luer-Lok (phi = 2.3 mm) port connections between the extraco rporeal tubing and the plasma separation chambers, which resulted in excess ively 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 mod ified circuit HRD was divided into the SMALL PORT group (phi = 2.3 mm, A = 4.15 mm(2)) and the LARGE PORT group (phi = 4.2 mm, A = 13.85 mm(2)) in adu lt swine (70 +/- 5 kg) given 300 U/kg heparin. A dual lumen cannula was ins erted 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 pr essure ranged from 447 +/- 21 to 452 +/- 27 mm Hg in the SMALL PORT group a nd from 190 +/- 14 to 204 +/- 19 mm Hg in the LARGE PORT group (p < 0.01 be tween groups). There were no significant differences in ACT between groups. We conclude that enlarged chamber ports significantly lower circuit pressu res for the HRD without changing heparin removal capability.