Bleeding is a well-known problem when cardiopulmonary bypass with full systemic heparinization is used for distal support during aortic cross-clamping. The recent advent of heparin-coated cardiopulmonary bypass equipment prompted our review of 91 consecutive patients who underwent repair of descending thoracic and thoracoabdominal aortic aneurysms. Two different surgical techniques were used: 42 of 91 patients had simple aortic cross-clamping and rapid reanastomosis, whereas 49 of 91 had distal support using all heparin-coated perfusion equipment with low systemic heparinization (100 IU/kg body weight; activated coagulation time > 180 seconds). Baseline parameters, location (thoracoabdominal: 28/91; 31%), and type of aneurysm (ruptured: 14/91; 15%) were similar in both groups. Cross-clamp time was 37 +/- 22 minutes for support versus 29 +/- 13 minutes for simple clamping (p < 0.05). There were fewer revisions due to bleeding for support (1/49 patients; 2%) versus simple (4/42; 10%; p < 0.05) and fewer patients with impaired renal function requiring temporary hemofiltration for support (4/49 patients; 8%) versus simple (6/42; 14%). Hospital mortality was lower for support (5/49; 10%) versus simple (8/42; 19%). Transfusion requirements during operation were 3,732 +/- 3,458 mL for simple versus 3,392 +/- 2,058 mL for support (not significant). Chest tube drainage totaled 982 +/- 1,102 mL for simple versus 720 +/- 618 mL for support (not significant). The total volume requirements were 8,156 +/- 4,753 mL for simple versus 7,495 +/- 3,342 mL for support (not significant) during operation and 4,416 +/- 2,422 mL for simple versus 3,380 +/- 1,432 mL for support (p < 0.025) during the 24 hours after operation.(ABSTRACT TRUNCATED AT 250 WORDS)