An investigation into new materials for extracorporeal life support including mechanical properties, blood surface interactions and the inflammatory response to bypass
2014-12-15T10:31:14Z (GMT) by
INTRODUCTION: Extracorporeal Membrane Oxygenation (ECMO) causes coagulation and inflammation. Also pump tubing can rupture. Therefore new tubing is needed.;AIMS: To compare mechanical properties and biocompatability of two potential ECMO tubings (LVA and SRT) with Tygon (current tubing). To develop a novel porcine veno-venous ECMO model. To review ECMO results at Glenfield Hospital.;METHODS:.;I) Mechanical: Durability; roller pump and test rig. Wear; electron microscopy. Spallation; laser diode particle counter.;II) In-Vivo Biocompatability: 5 pigs for each material, 48 hours veno-venous perfusion, samples: Blood count, blood gases, Prothrombin, Thrombin and Activated Partial Thromboplastin times, Lactoferrin, C3adesarg and Thromboxane B2. Lung neutrophil immunohistochemistry, histology and lung water.;III) In-Vitro Biocompatability: a) 5 circuits of each material recirculated for 6 hours, human blood. Samples as above plus fibrinogen, C5b-9 instead of C3adesarg.;b) I125Fibrinogen uptake with and without albumin washing.;IV) Clinical Review: Retrospective.;RESULTS:;I) Mechanical: Tygon was unpredictable, but better than LVA and SRT.;II) In-Vivo Biocompatability: The porcine model was successfully established. The only significant difference between groups was higher haemolysis with Tygon compared to SRT. Animals developed "ARDS" and thrombocytopenia.;III) In-Vitro Biocompatability: a) SRT and LVA, increased coagulation. LVA increased haemolysis. b) Untreated Tygon, lower fibrinogen uptake, no differences after albumin.;IV) Clinical Review: (n) and % survival: Respiratory; Adult (99) 63%, Paediatric (81) 77%, Neonatal (134) 75%. Cardiac; Adult (8) 38%, and Paediatric (28) 61%. Results for the first 50 adult respiratory patients: mean PaO2/FIO2. 65 36.9 mmHg, mean Murray score 3.4 0.5 and 66% survival. Compared to historical controls (55.6% & 42% survival) p=0.036 & p=0.0006.;CONCLUSIONS: Neither SRT nor LVA are mechanically adequate for ECMO. SRT and LVA are less biocompatable than Tygon, causing more coagulation and haemolysis. The porcine model was technically successful but needs larger numbers to discriminate between materials.