Evaluation of Chitosan as a New Hemostatic Agent: in Vitro and in Vivo Experiments

Abstract

Life-threatening bleeding through the pores of vascular grafts is a well-recognized complication in major cardiac and thoracic aortic surgery despite the use of low porosity dacron grafts (1, 2). There have been a number of investigations in which this situation is improved by the preclotting of the grafts, and Bethea and Reemtsmak (l) have described a process wherein the graft was autoclaved after immersion of the graft into heparinized blood. Cooley (3) has since modified the technique by immersion of the grafts in plasma rather than blood, and then autoclaving. He found that this improved the handling characteristics of the grafts. More recently, Malette et al. (4) described the use of a new hemostatic agent, chitosan. They replaced the abdominal aorta of dogs by grafts which had been treated in chitosan and found, at autopsy, that the grafts were encased in smooth muscle, with a living endothelial lining and an abundant vasa-vasorum. The control grafts showed the usual fibrous healing. They also found the chitosan-treated grafts to be impermeable to blood. Following these observations, we decided to investigate the use of chitosan as a hemostatic agent in critical situations, mimicking in vivo cardio-pulmonary bypass conditions where patients are given high doses of heparin systemically. We also looked at the effect of chitosan on graft healing and pseudointima formation. Several techniques for the treatment of the grafts with chitosan were used.