Embolism is an uncommon complication of altered mentation after invasive procedures, but it must be placed on the list of differential diagnoses. The four most common emboli seen in the critical care patient population are air, fat, cholesterol, and blood emboli (clots).

Air embolism occurs when air enters the systemic vascular circulation during placement or removal of a central venous catheter or at other times when a central venous catheter is in use. Air can also be introduced into the systemic circulation during cardiac surgery procedures, neurosurgical procedures, and endoscopic procedures. Air that enters the venous circulation can travel to the right side of the heart and cause cardiopulmonary compromise. The clinical presentation of a venous air embolism is highly variable and depends on the amount of air entry, the speed of entry, and the patient’s size and premorbid condition. Symptoms may range from mild chest discomfort to altered mentation to complete cardiovascular collapse. Alternatively, a right-to-left shunt can result in an embolus that enters the arterial circulation and causes cerebral ischemia. If a cerebral air embolus is suspected, then the head should be immediately lowered, a fraction of inspired oxygen of 1.0 should be delivered, and adequate ventilation maintained. One therapy for air embolus is hyperbaric oxygen therapy, which if desired, should be instituted within 5 h of neurologic or cardiac symptoms.