The key factors determining the degree of morbidity and mortality in venous air emboli are related to the volume of gas entrainment, the rate of accumulation, and the patient’s position at the time of the event.1,6,11
Generally, small amounts of air are broken up in the capillary bed and absorbed from the circulation without producing symptoms. Traditionally, it has been estimated that more than 5 mL/kg of air displaced into the intravenous space is required for significant injury (shock or cardiac arrest) to occur. However, complications have been reported with as little as 20 mL of air (the length of an unprimed IV infusion tubing) that was injected intravenously. The injection of 2 or 3 mL of air into the cerebral circulation can be fatal.Furthermore, as little as 0.5 mL of air in the left anterior descending coronary artery has been shown to cause ventricular fibrillation.13Basically, the closer the vein of entrainment is to the right heart, the smaller the lethal volume is.