Thrombus formation on the balloon of heparin-bonded pulmonary artery catheters: an ultrastructural scanning electron microscope study.

Abstract

To investigate heparin-bonded pulmonary artery catheters with respect to thrombus formation and platelet aggregation at the balloon and the shaft using a scanning electron microscope in critically ill patients. Prospective study. Critical care unit and research laboratories. Pulmonary artery catheters were inserted in critically ill patients (n = 10). Pulmonary artery catheters were removed after 24, 48, 72, or 120 hrs, and the ultrastructure was investigated in specialized research laboratories. Balloon and shaft were investigated using a scanning electron microscopic technique. Area of thrombus formation was quantified using image analysis. Heparin release of the catheters was measured. The frequency of balloon inflations was investigated in in vitro experiments by inflating catheters different times (0, 10, 20, and 30 times). Twenty-four hours after catheter insertion, scanning electron microscopic images showed thrombus formation and platelet aggregation at the site of the balloon. Seventy-two hours after catheter insertion, a thrombus started to detach. The areas of thrombus formation did not differ, but thrombus organization changed dramatically 72 and 120 hrs after catheter insertion. The shaft was colonized by single cells only. Cracks of the balloon could be observed after 72 hrs, whereas no cracks could be found in in vitro controls. In vitro, heparin release of the pulmonary artery catheters decreased significantly after 24 hrs. Scanning electron microscopic images of heparin-bonded pulmonary artery catheters demonstrate thrombus formation on the balloon 24 hrs after pulmonary artery catheter insertion, increasing dramatically at 72 and 120 hrs. The shaft was colonized by single cells only. The thrombus size is not significantly different during the observation time, but the grade and quality of thrombus formation differ.