Low-dose versus high-dose heparinization during arteriovenous carbon dioxide removal

The purpose of this study was to compare low-dose (LD) and high-dose (HD) systemic heparinization in a prospective randomized study of arteriovenous carbon dioxide removal (AVCO₂R) during acute respiratory distress syndrome, using a commercially available heparin-coated oxygenator. Adult sheep (n = 13) received an LD₅₀ smoke inhalation and 40% TBSA third degree cutaneous flame burn injury. At 40-48 h post-injury, animals underwent cannulation of the carotid artery and jugular vein and were then randomized to HD heparin (activated clotting time, ACT > 300 s, n = 6) and LD heparin (ACT < 200 s, n = 7) and placed on AVCO₂R for approximately 72 h using an oxygenator with the Trillium Bio-Passive Surface ^TM. Mean ACTs were significantly different, as expected (HD: 446 ± 26 s, LD: 213 ± 12 s, p < 0.05). AVCO₂R shunt flow averaged approximately 13% of cardiac output with mean CO₂ removal similar in HD and LD, p = NS. The hematocrit, platelet count, and fibrin degradation products for the two groups were not different. No differences in thrombosis or bleeding were noted. In conclusion, LD systemic heparin (ACT < 200 s) with a heparincoated oxygenator does not increase thrombogenicity during AVCO₂R for smoke/burn-induced severe lung injury in sheep.