Uncoated and coated blood contact surfaces of a hollow-fiber oxygenator: an in-vitro comparison

Objective

The hemocompatibility of oxygenators (OX) can be improved by coating of blood contact surfaces with biopolymers. In the new Trillium (TR) coating of the Affinity hollow-fiber OX, the blood-OX interaction was attempted to reduce by using two structurally different polymer layers. The aim of this in-vitro experiment was the comparison of both physical properties and hemocompatibility of TR-coated OX with the uncoated (UC) and AOThel-coated (AO) versions.

Method

For the experiment, three standardized circuits used, each with a roller-pump (flow rate:5 l/min) and a separate reservoir. The priming volume was a mixture of fresh, heparinized (100 IE/ml) human blood and Ringer's lactate solution (Hb:8.0 g/dl). During a 180-min total circulation time, the blood temperature was reduced from 37°C to 20°C for 30min after 120 min of per fusion. At the beginning and every 30min of the circulation, blood count, free Hb, thrombocytic hemostasis (tPA, d-dimer, prothrombin fragments F1+2, TAT), PMN-elastase and complements C3c + C5a determined. In addition, the pressure drop was obtained. Scanning electron microscopic images of fibers, heat exchangers and OX-housing were performed after completing the experiment.

Results

The biggest pressure drop was in TR and lowest in UC. The latter showed the lowest hemolysis ratio; however, the thrombocyte consumption in UC was higher than in AO and TR. A significant difference between AO and TR was not found. Scanning electron microscopy showed clearly more accumulations of cellular blood elements and an increased aggregation of leukocytes on the UC-surface, compared to AO and TR, which in between displayed no remarkable differences.

Conclusions

1. The pressure drop in coated systems is higher in the UC. 2. UC shows clear disadvantages in thrombocyte consumption and cellular adhesion compared with AO and TR, while significant differences could not be verified between AO and TR. 3. UC has a lower hemolysis tendency in comparison to coated systems, which is subject of a further investigation.