The Aspiration of Injected Air via an Epidural Catheter as an Indicator for Appropriate Placement of the Catheter in the Epidural Space

Background: The gold standard for proper epidural catheter positioning is a clinical response, as assessed by a pinprick test. Yet it may take time or it may be difficult to perform this test after epidural catheter placement in sedated or uncooperative patients or during general anesthesia. We assessed the usefulness of aspirating injected air via an epidural catheter as an indicator of correct epidural catheter placement. Methods: We surveyed 200 patients who underwent surgery under general or epidural anesthesia. A Tuohy needle was inserted into the epidural space with using the hanging drop technique. After placement of the epidural catheter, 3 ml of air was injected via the catheter, and then the volume of aspirated air was measured. Results: The mean volume of aspirated air was 2.3 ± 0.7 ml (75% of the injected air volume) and this ranged from 0 to 3 ml. Conclusions: Aspiration of injected air is a simple alternative method for identifying the appropriate placement of epidural catheters in the epidural space. (Korean J Pain 2009; 22: 124-129)