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

Objective: To investigate heparin-bonded pulmonary artery catheters with re spect to thrombus formation and platelet aggregation at the balloon and the shaft using a scanning electron microscope in critically ill patients. Design: Prospective study. Settings: Critical care unit and research laboratories. Patients: Pulmonary artery catheters were inserted in critically ill patien ts (n = 10). Interventions: Pulmonary artery catheters were removed after 24, 48, 72, or 120 hrs, and the ultrastructure was investigated in specialized research l aboratories. Measurements and Main Results: Balloon and shaft were investigated using a scanning electron microscopic technique. Area of thrombus formation was qua ntified using image analysis. Heparin release of the catheters was measured . The frequency of balloon inflations was investigated in in vitro experime nts by inflating catheters different times (0, 10, 20, and 30 times). Twent y-four hours after catheter insertion, scanning electron microscopic images showed thrombus formation and platelet aggregation at the site of the ball oon. Seventy-two hours after catheter insertion, a thrombus started to deta ch. The areas of thrombus formation did not differ, but thrombus organizati on 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 vi tro, heparin release of the pulmonary artery catheters decreased significan tly after 24 hrs. Conclusions: Scanning electron microscopic images of heparin-bonded pulmona ry artery catheters demonstrate thrombus formation on the balloon 24 hrs af ter 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.