Rheopak Surface Coating

Extracorporeal cardiopulmonary support unavoidably exposes blood to foreign surfaces*, and this exposure could increase the risk of platelet activation1 and surface adhesion that can consequently lead to complications such as Thromboembolism, Haemorrhaging and Inflammation2.

To reduce this risk, Chalice Medical has developed the RHEOPAK bio-passive surface coating.

Rheopak’s proprietary formulation contains a synthetic albumin, which improves the biocompatibility of the support circuit by significantly reducing platelet aggregation and adhesion to oxygenator fibers3, and has been shown to maintain a presence for up to 15 days of continuous circulation with almost no wash off during the initial stages of support4

Rheopak is biologically inert

It also does not contain bioactive substances or substances derived from animals as other Heparin based coatings do, thus allowing it to be suitable for use with patients susceptible to heparin-induced thrombocytopenia (H.I.T patients).

An important and fundamental element used in Rheopak is an entirely “synthesised” Albumin.  This characteristic offers several advantages over other plasma sourced human serum albumin coatings5, such as:

• Absence of animal derived products and, known or unknown human pathogens,
• Continuity of supply and batch to batch consistency,
• High purity, high homogeneity and high free thiol content,
• The absence of host derived proteases,
• Supplied under the presence of an established regulated pathway.

Non-coated Oxygenator fiber after 6 hours exposure to whole human blood in vitro

Coated Oxygenator fiber after 6 hours exposure to whole human blood in vitro

Images captured from an electron microscope at 200 times magnification “clearly shows adhesion of platelets to the uncoated oxygenator gas exchanger fibres with little or no platelet adhesion to coated fibres3. (click on image to expand).

Suitability

The application of Albumin in coating medical products is well established over many years.  It has a predisposition to cover both hydrophobic and hydrophilic surfaces6, it is reported to prevent surface adsorption, aggregation, fibrillation and oxidisation5, and observations point to a trend in patients treated with albumin coating receive less red blood cell transfusions7.

Through a highly controlled and monitored process, the coating is formulated and applied in a class-7 cleanroom through a custom-made transfer and drying system.  Rheopak is applied as standard to all bypass and ECMO Paragon Oxygenators, and upon request, may also be applied to other single use products such as Cannula, heat exchangers and customised tubing packs.

1)   Rinder CS1, Bohnert JRinder HMMitchell JAult KHillman R. (1991). Platelet activation and aggregation during cardiopulmonary bypass. NCBI [online].  Available at: https://www.ncbi.nlm.nih.gov/pubmed/1716077.

2)   Weerasinghe, A and Taylor, M (1998). The Platelet in Cardiopulmonary Bypass.

3)   Heptinstall, S. (2017). In Vitro Investigation of Platelet Adhesion to Uncoated and Coated Oxygenator Fibre Surfaces. Platelet Solutions.

4)   Investigation in to recombumin albumin coating.  Internal verification and validation study by C.Sutton at Chalice Medical (2016),

5)   The use of albumin in formulation, Albumedix 2016.

6)   Kowalczynska H.M, Nowak-Wyrzykowska M, Szczepankiewicz A.A, Dobkowshi J, Dyda, M, Kaminski J, Kolos R: Albumin absorption on unmodified and sulfonated polystyrene surfaces, in relation to cell-substratum adhesion. Coll Surfaces B Biointerfaces (2011) 84 536-554.

7)   Chen L, Lv L, Long C and Lou S (2016). Effects of circuit albumin coating on coagulation and inflammatory response for patients receiving aortic arch replacement: a randomized controlled trial. NCBI [online]. Available at: https://www.ncbi.nlm.nih.gov/pubmed/27117175 [accessed 26.6.18]

*Polycarbonate (PC), Polyvinyl chloride (PVC), Polyester, Polyurethane (PU), Polypropylene (PP), Polymethylpentene (PMP).