Session 3: Innovative Solutions To Common Perfusion Challenges Using Oxygen Manipulation

If a patient should suffer a massive air embolus on CPB, several steps should be rapidly taken:

1. The sweep gas FiO2 should immediately be increased to 100% oxygen to start off gassing the nitrogen.
2. The patient should be placed in a Trendelenburg position (head down) and, if possible, on his left side (left lateral decubitus position). This positioning helps to trap air in the apex of the ventricle.
3. Thiopental or some other barbiturate should be used to reduce brain activity, oxygen consumption and intracranial pressure.
4. Profound hypothermia should be induced for 60 minutes. This will reduce oxygen consumption. Hypothermia will also increase the solubility of the nitrogen so it can be more easily off gassed. It will also protect against reperfusion injury once the brain capillaries are reopened.
5. After CPB, the head injury protocol of barbiturate coma and moderate hypothermia should be used. Retrograde cerebral perfusion is of questionable benefit.

High antegrade blood flow to the brain with cold, 100% oxygenated blood will probably remove the nitrogen more rapidly and effectively than the slower retrograde venous-to-arterial blood flow. The anesthesiologist may try to perform carotid compression as the embolus is occurring. But the reaction time would need to be almost instantaneous. Carotid compression is also of questionable benefit and may limit the anesthesiologist’s other timely and necessary responses.

Air embolism from the right side of the heart to the left side is often overlooked, but can occur in the presence of an unknown cardiac defect such as on open PFO or PDA or an unrepaired ASD or VSD. The air can enter the right side from an open intravenous or central line, from around the venous cannula purse strings due to siphon or vacuum assist or during a right atriotomy or ventriculotomy. During a true open heart procedure, the evacuation of air from the left side of the heart before the removal of the aortic cross clamp may be very difficult.