Effects of venous air embolism on the cardiovascular system and acid base balance in the presence and absence of nitrous oxide.

Cardiovascular responses and acid-base changes with graded volumes of intravenously injected air were measured in dogs anesthesized with pentobarbital and either 100% oxygen or 50% oxygen and nitrous oxide. Mean arterial blood pressure decreased significantly with 2.5 ml of air/kg in the oxygen group and at all volumes in the nitrous oxide group. The volume of air embolus appeared to increase more than twice in the presence of 50% nitrous oxide. Pulmonary artery wedge pressure increased significantly in both groups, while end-tidal carbon dioxide decreased significantly in both groups. The changes in pulmonary artery wedge pressure and end-tidal carbon dioxide were simultaneous, suggesting that the less invasive monitoring technique may be utilized in diagnosing significant air embolism. Right atrial pressure increased while left atrial pressure decreased significantly in both groups. With injected volumes of 2.0 and 2.5 ml or air/kg, right atrial pressure exceeded left atrial pressure creating the potential of paradoxical air embolism. The pH and PaO2 decreased while PaCO2 increased significantly during air embolization.