You can use ultrasound to identify landmarks and assist in the placement of an epidural, but it does not guarantee the catheter will end up in the epidural space. That's why loss-of-resistance training for the gold standard landmark-based technique is important. An inexpensive way to practice involves grabbing a banana from the break room and taping it to an inflated surgical glove. Advancing the large gauge, blunt-tip Tuohy needle through the banana peel mimics going through the supraspinous and interspinous ligaments, as well as the ligamentum flavum. You'll feel the loss of resistance once the needle goes through the peel and is in the banana itself, which is what it feels like when the needle passes through these ligaments and into the epidural space. Moving the needle through the back of the banana and popping the glove simulates entering the patient's spinal space. This is known as a "wet tap," and shouldn't happen.
Nadia Hernandez, MD
Texas Medical Center