Improved distal circulatory support for repair of descending thoracic aortic aneurysms

Abstract

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. After declamping of the aorta the mean arterial pH dropped to 7.29 ± 0.10 for simple clamping as compared with 7.37 ± 0.08 for clamping supported with partial cardiopulmonary bypass ( p < 0.0005), partial arterial CO 2 pressures increased to 6.44 ± 1.21 kPa for simple as compared with 5.22 ± 1.09 kPa ( p < 0.0005), and mean negative base excess values increased to 4.9 ± 5.8 for simple as compared with 2.6 ± 3.9 ( p < 0.05). No device failure occurred. We conclude that proximal unloading and support of distal circulation during resection of descending thoracic and thoracoabdominal aortic aneurysms prevents declamping shock and can now be realized without risk of bleeding complications. This approach provides superior hemodynamics and oxygenation.