17 Mar

Pathogenesis of Cerebral Air Embolism during Neodymium-YAG Laser Photoresection: Discussion

Although the “acute carcinoid syndrome” has been previously reported during flexible fiberoptic bronchoscopy in a patient with an endobronchial carcinoid and was also a clinical consideration in our patient, this cause appears unlikely. Serotonin is reported to cause hypertension in the carcinoid syndrome, whereas hypotension has been attributed to the effects of bradykinin, histamine, and tachykinins. Also, serotonin, as mediated through norepinephrine release, and histamine may induce arrhythmias. These mechanisms appear remote in light of the normal measured values for serotonin and 5-HIAA in our patient and no severe hemodynamic aberration.

In our case, an air embolism presumably occurred as a result of positive-pressure ventilation during laser photoresection of a highly vascular tumor. The introduced venous air may potentially cause arterial embolism by passing through a patent foramen ovale, which is present in 27.3 percent of the general population. A two-dimensional echocardiogram did not reveal a septal defect in our patient. Alternatively, large quantities of venous air may traverse the pulmonary capillaries and reach the pulmonary venous effluent. The observed initial tachyarrhythmia and ST segment depression may be attributed to transient coronary artery involvement. The “pale discoloration over the abdomen” is consistent with the marbling of the skin seen when subcutaneous air bubbles cause venous stasis. We do not believe that Wang needle aspirations nor endobronchial biopsies contributed to the occurrence of air embolism, since these procedures were done at the inception, 2Vz hours prior to the manifestations of embolism. The marked neurologic improvement in this patient when treated in a hyperbaric chamber is highly suggestive of an acute air embolism. 
We conclude that this potentially catastrophic event may complicate an endobronchial procedure such as Nd-YAG laser photoresection. Early recognition and intervention may prevent grave outcomes.

Categories: Air Embolism
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