The effects of halothane and pentobarbital on the threshold of transpulmonary passage of venous air emboli in dogs.

The influence of halothane, pentobarbital, and their interaction on the passage of air across the pulmonary circulation was studied in 12 dogs using transesophageal M-mode echocardiography for air detection in the left atrium and/or aorta. Air was detected in the left atrium and/or aorta after pulmonary artery air injection of 0.04 ml/kg during 1% halothane anesthesia (n = 5). Addition of pentobarbital changed the threshold to 1.0 ml/kg. During pentobarbital anesthesia with and without halothane (n = 7), the thresholds were 1.1 and 1.2 ml/kg, respectively. The authors conclude that the threshold for transpulmonary passage of venous air is higher during anesthesia with pentobarbital with or without halothane than during anesthesia with halothane alone.