A prospective comparison of atrio-femoral and femoro-atrial flow in adult venovenous extracorporeal life support

Introduction: In the United States, venovenous extracorporeal life support has traditionally been performed with atrial drainage and femoral reinfusion (atrio-femoral flow). Although flow reversal (femoro-atrial flow) may alter recirculation and extracorporeal flow, no direct comparison of these 2 modes has been undertaken. Objective: Our goal was to prospectively compare atrio-femoral and femoro-atrial flow in adult venovenous extracorporeal life support for respiratory failure. Methods: A modified bridge enabling conversion between atrio-femoral and femoro-atrial flow was incorporated in the extracorporeal circuit. Bypass was initiated in the direction that provided the highest pulmonary arterial mixed venous oxygen saturation, and the following measurements were taken: (1) maximum extracorporeal flow, (2) highest achievable pulmonary arterial mixed venous oxygen saturation, and (3) flow required to maintain the same pulmonary arterial mixed venous oxygen saturation in both directions. Flow direction was then reversed, and the measurements were repeated. Data were compared with paired t tests and are presented as mean ± standard deviation. Results: Ten patients were studied, and 9 were included in the data analysis. Femoro-atrial bypass provided (1) higher maximal extracorporeal flow (femoro-atrial flow = 55.6 ± 9.8 mL/kg per minute, atrio-femoral flow = 51.1 ± 11.1 mL/kg per minute; P = .04) and (2) higher pulmonary arterial mixed venous oxygen saturation (femoro-atrial flow = 89.9% ± 6.6%, atrio-femoral flow = 83.2% ± 4.2%; P = .006); (3) furthermore, it required less flow to maintain an equivalent pulmonary arterial mixed venous oxygen saturation (femoro-atrial flow = 37.0 ± 12.2 mL/kg per minute, atrio-femoral flow = 46.4 ± 8.8 mL/kg per minute; P = .04). Conclusions: During venovenous extracorporeal life support, femoro-atrial bypass provided higher maximal extracorporeal flow, higher pulmonary arterial mixed venous oxygen saturation, and required comparatively less flow to maintain an equivalent mixed venous oxygen saturation than did atrio-femoral bypass. (J Thorac Cardiovasc Surg 1998;116:628-32)