We appreciate the expertise of Drs. Moon and Camporesi in the field of undersea and hyperbaric medicine and thank them for their input on this topic. We readily acknowledge that the Trendelenburg position is detrimental to patients with intracranial hypertension and known cerebral air embolism. Our recommendation focused on the use of the Trendelenburg position for the prevention of cerebral air embolism in the setting of aortic air embolism, acknowledging that the data on this topic are sparse. Drs. Moon and Camporesi propose that the Trendelenburg position should not be used to prevent cerebral air embolism, based on a 1988 study on 10 dogs that examined the effect of varying degrees of Trendelenburg on the appearance of bubbles in the carotid artery when air was injected into the left ventricle or aorta. This study found that air appeared in the carotid regardless of the degree of Trendelenburg. However, the study did not attempt to quantify changes in the amount of air that reached the carotid with changes to the degree of Trendelenburg. This is an important distinction because, although no air emboli to the brain is best, smaller amounts of emboli are still better than larger amounts of emboli. Consequently, more qualitative study on this topic is needed to determine the appropriate role for Trendelenburg in the prevention of cerebral air embolism.
Similarly, lidocaine infusion may have some theoretical efficacy in the treatment of coronary air embolism, but this remains unproven in humans. Thus, we chose to focus on more conventional, although admittedly less creative interventions. As Dr. Moon mentions, however, this intervention is fairly benign and could likely be trialed without significant risk.
Finally, Dr. Moon and Camporesi note that these authors do not mention hyperbaric oxygen as a treatment for coronary artery air embolism. We chose not to include hyperbaric oxygen in our recommendations because of significant concerns regarding its expediency and availability in the emergent setting. Coronary air embolism typically results in either cardiac arrest or periarrest, associated with profoundly decreased cardiac output. Treatment is restoration of whole-body circulation by the most effective and expedient means possible. Although effective for dissolving arterial air, hyperbaric oxygen treatment is not the most effective or expedient means of restoring circulation in the setting of cardiac arrest. Most hospitals in the United States do not have access to a hyperbaric oxygen chamber, and in those that do, transport and treatment of an arresting patient within one is logistically complex at best. Recent validated data published in Undersea and Hyperbaric Medicine reports that only 43 centers in the United States “had the equipment, intravenous infusion pumps and ventilators, and staff necessary to treat high-acuity patients.” For these reasons, we chose to focus our recommendations on interventions that would be readily available to the majority of practicing anesthesiologists.