Utility of Ultrasound in Evaluating an Ambiguously Working Thoracic Epidural: A Case Series

A thoracic epidural is commonly used for analgesia following trauma or surgery. Traditionally, thoracic epidurals are performed using the loss of resistance technique. However, false-positive loss of resistance and catheter placement outside the epidural space is possible. In such scenarios and when clinical equivalents, such as hemodynamic changes and sensory loss to epidural blockade, fail as well, assessment of the catheter position can be accomplished using ultrasound. Ultrasound scanning can identify the catheter and spread of the injectate past the laminas to confirm its epidural positioning. In addition, multiple scanning approaches can be used to view the interlaminar spaces at the thoracic level, which are usually challenging to visualize compared to the lumbar level to verify the epidural catheter. It can be done at the bedside, in real-time, and with the feasibility of obtaining immediate results. This way, a nonfunctioning catheter can be replaced promptly to achieve adequate analgesia. We present a case series of patients in whom an ultrasound was utilized to evaluate and replace ambiguously working thoracic epidural catheters that were primarily placed by the loss of resistance technique.