The effect of left heart bypass on pulmonary blood flow and arterial oxygenation during one-lung ventilation in patients undergoing descending thoracic aortic surgery

Abstracts Study Objective To study the effect of left heart bypass (LHB) on regional pulmonary blood flow and arterial oxygenation during one-lung ventilation (OLV). Design Prospective, observational study Setting Operating room Patients 14 ASA physical status II and III patients scheduled to undergo descending thoracic or thoracoabdominal aortic surgery using LHB. Interventions and Measurements Parameters studied during OLV with 100% oxygen before and during LHB mean arterial pressure, heart rate, pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, cardiac index, cardiac output, arterial oxygen tension (PaO 2 ), mixed venous oxygen pressure, alveolar arterial oxygen difference (P (A-a)O2 ), and right upper pulmonary venous flow (RUPVF). Right upper pulmonary venous flow was measured using transesophageal echocardiography. Main Results With the transition to OLV, there was a significant decrease in PaO 2 and a significant increase in P (A-a)O2 . However once LHB was initiated, these values improved significantly ( P = 0.0007 and 0.0004, respectively) with the simultaneous increase in RUPVF ( P = 0.0018). Conclusions LHB improved pulmonary blood flow to the dependent lung and arterial oxygenation during OLV in descending thoracic aortic surgery.