Evaluation of the Accuracy of Real-time Ultrasound-assisted Thoracic Epidural Catheter Insertion: a Pilot Study

Thoracic epidural anesthesia has been associated with reduced acute postoperative pain for a wide variety of surgical procedures. It has also been associated with reductions in perioperative cardiac stress, chronic post-thoracotomy pain, and improvements in postoperative pulmonary function. Although a variety of methods can be used to confirm the position of the epidural needle in the epidural space, a blind technique and fluoroscopic guided approach are a widely used method. A thoracic epidural block is a relatively more difficult procedure than procedures used in other regions, because the spinous process of the thoracic vertebra is longer than that of the lumbar vertebra, and the area through which the needle can approach the epidural space is relatively smaller due to an acute angle and larger distance between the skin and the epidural space. Therefore, the success rate of thoracic epidural intervention is only about 68% under a blind technique due to inadequate position of the needle tip, misplacement, occlusion, and migration of the catheter.

Although fluoroscopic guided thoracic epidural intervention is the safest and most accurate method to identify the correct anatomical structures and confirm the epidural space with contrast medium, its use is limited because of the difficulty of using fluoroscope and the burden of radiation exposure. As the use of ultrasound has become popularized and universal, it has been widely used in regional anesthesia and analgesia, has continuously replaced the modality such as a blind technique and fluoroscopic guidance. Ultrasound-guided thoracic epidural catheter insertion was also recently investigated, and then it was conducted successfully in 15 cases of thoracic and upper abdominal surgery. Moreover, it showed several advantages including lowering the number of needle passes and increasing the success rate. However, it has not yet been studied how accurately the catheter is located in the thoracic epidural space during thoracic epidural catheter insertion using real-time ultrasound. Although it is possible to speculate the success of the thoracic epidural catheterization clinically, the identification of the location of the catheter is only possible under fluoroscopic guidance. Therefore, in the present study, we aimed to confirm the success rate of ultrasound-guided thoracic epidural catheter insertion, using fluoroscopy with contrast medium.