To the Editor:
We read with interest the description by Oesterling et al. of a case of coronary artery air embolism. Their article nicely showed imaging confirming arterial gas embolism, demonstrated one of the risks of percutaneous lung biopsy and factors that may increase that risk. The authors correctly recommended administration of 100% oxygen and support of blood pressure. However, we do not agree with their recommendation on Trendelenburg positioning to prevent cerebral air embolism. The hypothesis of this former recommendation was based on the concept of buoyancy of bubbles within the circulation and the assumption that the head-down position would cause bubbles to be distributed caudally rather than to the brain. However, studies have shown that buoyancy has little or no effect on arterial or venous intravascular air distribution. Additionally, cerebral gas embolism can induce intracranial hypertension which can be worsened by the head-down position; consensus guidelines developed by the Undersea and Hyperbaric Medical Society and published in reviews recommend a horizontal position. Lidocaine infusion is a relatively benign treatment, for which there is significant evidence for efficacy in animal studies as well as some human observations. Proposed mechanisms include inhibition of transmembrane ischemic ion fluxes that lead to presynaptic depolarization, inhibition of calcium influx and glutamate release, and attenuation of lipid peroxidation. Lidocaine also inhibits bubble-induced endothelial leukocyte adhesion, which can reduce local blood flow. Most surprising in Dr. Oesterling’s report is the lack of any mention of hyperbaric oxygen, the definitive treatment for arterial gas embolism. Hyperbaric oxygen in this setting has few absolute contraindications, such as severe cystic lung disease that could rupture during decompression and cause additional arterial gas embolism. Many hyperbaric facilities are equipped to treat critically ill patients who may be intubated and receiving pressors (such as the highly regarded hyperbaric facility at LDS Hospital in Salt Lake City, Utah).