Effect of foreign surface pacification with albumin, aprotinin, propofol, and high-density lipoprotein

Abstract

Foreign surface pacification may significantly reduce the detrimental effects of the cardiopulmonary bypass (CPB) circuit. To date, albumin is the only intervention consistently shown to be beneficial. The cationic physical properties of aprotinin and the known negative charge on the plastic CPB circuit mean that aprotinin binds to the CPB circuit and membrane oxygenator. A previously validated model involving a parallel plate glass slide technique was used. The effects of albumin, aprotinin, propofol, and high-density lipoprotein (HDL) were assessed by the ability to inhibit platelet adhesion to the glass slide surface. The experiment was repeated with collagen-coated glass slides to reproduce the clinical effect of endothelial denudation. The interventions were repeated on membrane oxygenators that are used for CPB. Aprotinin resulted in a minimal reduction in platelet adhesion to uncoated or collagen-coated glass slides. HDL significantly reduced platelet adhesiveness to uncoated or collagen-coated glass slides. Human albumin solution (HAS) and propofol produced an intermediary inhibitory effect on platelet adhesion on both collagen-coated and uncoated glass slides. The same effect was seen with membrane oxygenators that are used during CPB. HDL produced a significant reduction of neutrophil activation when used to coat a membrane oxygenator. Foreign surface pacification with HDL may have beneficial effects as assessed by platelet adhesiveness in a parallel plate assay. Aprotinin had minimal effect, and propofol had an intermediate effect. The same results were obtained using membrane oxygenators, confirming the validity of the parallel plate technique as clinically valid.

Figure 1.

Parallel plate chamber used to visualize platelet attachment and spread over coated glass surfaces using video-enhanced light microscopy. The parallel plate chamber was made by producing a gap between a 20 × 20-mm glass coverslip placed on top of a 24 × 50-mm glass coverslip separated by glass coverslips.

Figure 2.

Schematic drawing of video-enhanced light microscopy setup.

Figure 3.

A, Typical view of adherent and activated platelets on the glass slide surface. B, Image after software image processing allowing the easy counting of adherent platelets. R, platelet is round and unattached; D, platelet is in dendritic stage with the dendrites attached to the surface; S, platelet is fully spread over the surface; PA, platelet aggregates; RBC, red blood cell.

Figure 4.

Percent platelet attachment on uncoated glass, HAS-coated glass, propofol-coated glass, and HDL-coated glass as a factor of time of platelet exposure to the surface.

Figure 5.

Percent platelet attachment to collagen type I–, HAS-, aprotinin-, propofol-, and HDL-coated collagen, as a function of time.

Figure 6.

Platelet sequestration by mock CPB circuit.

Figure 7.

Neutrophil activation as assessed by myeloperoxidase levels.