Risk factors for air embolization during cannulation of the ascending aorta

Several techniques have evolved for the cannulation of the ascending aorta for cardiopulmonary bypass. Although the theoretical risk of air embolization related to cannulation of the aorta has been alluded to in the past, studies of this problem have not previously been reported. Using a mock circulatory circuit, we found that cannulation with an empty clamped cannula caused a mean embolization of 0.0435 cc of air per cannulation compared to 0.0142 cc with a saline filled cannula and 0.0045 cc with a vented cannula. The residual amount of air which embolized in the ideally vented cannula was caused by the air pocket found within the aorta above a tangentially applied excluding clamp and could be eliminated completely by not clamping the aorta.