Detection of entrapped intracardiac air with intraoperative echocardiography

Embolization of entrapped intracardiac air represents a significant risk to the patient undergoing open heart surgery. To date, there have been no means available to ensure that the heart is free of air prior to restoration of the circulation. To assess Whether M mode echocardiography can accurately detect intracardiac air, we studied 10 dogs during cardiopulmonary bypass. Randomly, air was or was not injected into the left ventricular cavity of the fibrillating heart. Intracardiac air could be recognized by the presence of a stippled granular pattern, or a loss of the discrete linear echoes or decreased far field echoes, or any combination of these three. In all, 131 random observations were made. When 1.0 cc of air was injected, sensitivity and specificity were both 100 percent, but when 0.2 cc was injected, sensitivity and specificity decreased to 86 and 58 percent, respectively. Thus, M mode echocardiography appears to provide a sensitive and specific tool for detecting intracardiac air.