Hazards of nitrous oxide administration in presence of venous air embolism.

Nitrous oxide administration in presence of venous air embolism results in its volume augmentation. The present case report of a 50-year old patient undergoing posterior fossa tumor excision in the sitting position demonstrates the hazards of nitrous oxide in presence of venous air embolism. Administration of 66% nitrous oxide 140 minutes after the incidence of air embolism resulted in a significant decrease of end-tidal carbon dioxide tension, moderate hypotension, and tachycardia, suggesting volume augmentation of the air embolism. The results of our case report are in contrast to that by Shapiro et al who noted that nitrogen washout following administration of 100% oxygen was complete 65 minutes after the occurrence of venous air embolism. Shapiro and colleagues suggest the use of nitrous oxide challenge as a diagnostic aid in deciding when lung excretion of intravascular air is complete. However, our case report implies that nitrogen washout was not complete 140 minutes after venous air embolism incidence. Accordingly, we recommend to stop nitrous oxide administration once air embolism is suspected and to refrain from its re-administration throughout the rest of surgery.