Removal of retained air during cardiac surgery with transesophageal echocardiography and capnography

Study Objective: To evaluate a new method for removal of retained air at the end of cardiopulmonary bypass (CPB) by end-tidal CO2 pressure (PETCO2) and pulmonary arterial pressure (PAP) monitoring and transesophageal two-dimensional echocardiography (TEE). Design: Prospective study. Setting: Cardiac surgery unit at a university hospital. Patients: 36 ASA physical status I, II, and III patients for open heart surgery. Interventions: The CPB reservoir was gradually raised to decrease venous drainage. Accordingly, the right heart began to receive the venous blood and eject it to the pulmonary artery. The vent existing in the left ventricle or the left atrium then collected any whole blood containing air bubbles that came from the pulmonary circulation. The air bubbles were confirmed by TEE to be removed and not to eject from the left ventricle to the systemic circulation. Measurements and Main Results: Levels of PETCO2, PaCO2, PAP, and the duration of the removal procedure were measured when a sufficient pulmonary circulation was established and the removal of retained air was considered to be satisfactorily accomplished by the absence of air bubbles, confirmed by TEE for more than 30 seconds. PETCO2, reached 28 +/- 4 mmHg during the removal of air, while PaCO2 reached 35 +/- 6 mmHg (p < 0.05). Mean PAP during removal of air reached 18 +/- 4 mmHg, which was approximately 90% of that before CPB. The duration time of removal of air was 9 +/- 2 min. Conclusions: PETCO2 and PAP are useful indicators of pulmonary circulation during this procedure for removal of air: PETCO2 of 25 to 30 mmHg and PAP of 90% of the prebypass level have been found to be necessary for the removal of air. Our technique for removal of air using PETCO2, PAP, and TEE enables us to satisfactorily eliminate residual air. (C) 1997 by Elsevier Science Inc.