During the placement of an epidural catheter, the 'loss of resistance' technique is used to identify the epidural space. Which of the following best describes the sensation felt when the needle enters the epidural space using this technique?

Explanation

The loss of resistance (LOR) technique relies on the principle that the ligamentum flavum offers significant resistance to the advancement of the needle and the injection of air or saline. Once the needle tip passes through the ligamentum flavum and enters the epidural space, this resistance suddenly disappears, allowing for easy injection of the medium (air or saline). A 'pop' might be felt with dural puncture, but this indicates entry into the subarachnoid space. A gritty sensation is felt *before* entering the epidural space, while passing through the ligamentum flavum. A free flow of cerebrospinal fluid from the needle hub indicates entry into the subarachnoid space.