EPIDURAL AIR INJECTION ASSESSED BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY

Background and Objectives. The object of this study, using transesopha geal echocardiography (TEE) in anesthetized patients, was to investiga te the occurrence of venous air embolism (VAE) when air is injected in to the epidural space. Methods. Six patients between the ages of 18 an d 50 years (ASA I-II) undergoing general anesthesia in a supine positi on for nonthoracic surgical procedures were studied. Prior to general anesthesia, an epidural catheter was placed into the epidural space us ing a Tuohy needle and a standard saline loss-of-resistance technique. Following verification of proper catheter placement, general anesthes ia was induced and the trachea intubated. Thereafter, a TEE probe was inserted into the esophagus. After a 10-minute control period, and dur ing continuous TEE videotape recording, 5 mL of air was rapidly inject ed into the epidural space through the epidural catheter. This was fol lowed 10 minutes later by the epidural injection of 5 mL of room-tempe rature preservative-free saline. Microbubble echo targets were quantif ied in a range from 0 to 4+. Results. Venous air microbubble emboli ap peared in the circulation within 15 seconds after injecting either air or saline into the epidural space. Conclusions. No evidence of clinic ally significant VAE was seen in any patient. The results suggest that drugs injected into the epidural space may have unexpectedly easy acc ess to the venous circulation with a potential to produce unwanted sys temic effects. Clinicians should be alert to the possibility that loca l anesthetics, or any other drug placed epidurally, may rapidly enter the systemic circulation even without the intravenous placement of an epidural catheter.