title: An in vitro method for comparing biocompatibility of materials for extracorporeal circulation.
abstract: We measured the response of fresh heparinized human blood to recirculation through circuits made of LVA (Portex Industries, Hythe, Kent, UK), SRT (Rehau UK, Langley, Slough, UK) and Tygon S-65-HL (Norton Performance Plastics, Corby, Northants, UK), as control. Circuit construction: 1/2 in. tubing, heat exchanger (Dideco D-720P), Stockert roller pump, just underoccluded, Cincinnati Sub Zero heater, circuit volume of 500 ml. Flow 3.45 l/min, 37 degrees C.
  
  
  METHODS
  at 10 min, 1, 2, 4 and 6 h. n=5 in each group; 2/5 SRT experiments were stopped at 45 and 60 min due to overpressurization.
  
  
  RESULTS
  Baseline activated clotting time (ACT) of 300 s, increasing in all groups as fibrinogen fell to zero with SRT and LVA. Minimum fibrinogen was 1 g/l for Tygon. Absolute thrombocytopenia occurred (SRT and LVA 60 min and Tygon 240 min). International normalized ratio (INR) in both the SRT and LVA circuits increased, but mean increase for Tygon (0.56) was smaller than the other two materials. Plasma free haemoglobin increased in all three materials; the increase was greater in the LVA circuits compared to the control. C5b9 levels increased equally in all groups. Lactoferrin levels rose equally in all groups to a maximum at 150 min. The neutrophil counts fell, mirroring the lactoferrin. The total white cell counts also fell in all groups; in the LVA circuits, the fall was significantly lower than in the control. Rapid disappearance of platelets and fibrinogen from the blood in the SRT and LVA circuits excludes them both from extracorporeal use. Paradoxically, SRT caused the least complement activation of the three materials. This method can be used to compare biocompatibility.
authors.affiliation: Department of Surgery, Glenfield Hospital, University Hospitals of Leicester NHS Trust, UK. ycq57@dial.pipex.com
authors.forename: Giles J
authors.initials: GJ
authors.lastname: Peek
authors.forename: Richard
authors.initials: R
authors.lastname: Scott
authors.forename: Hilliary M
authors.initials: HM
authors.lastname: Killer
authors.forename: Richard K
authors.initials: RK
authors.lastname: Firmin
mesh_terms: D000293:Adolescent; D000328:Adult; D001672:Biocompatible Materials / Q000494:pharmacology* / Q000592:standards; D015415:Biomarkers / Q000097:blood; D001777:Blood Coagulation; D005112:Extracorporeal Circulation / Q000295:instrumentation; D006801:Humans; D007249:Inflammation / Q000097:blood; D008422:Materials Testing / Q000379:methods*; D008875:Middle Aged; D011090:Polyenes / Q000494:pharmacology; D011143:Polyvinyl Chloride / Q000494:pharmacology; D012826:Silicone Elastomers / Q000494:pharmacology
chemical_list: D001672:Biocompatible Materials; D015415:Biomarkers; D011090:Polyenes; D012826:Silicone Elastomers; C035051:PL 732; D011143:Polyvinyl Chloride