Ultrasound-guided thoracic paravertebral puncture and placement of catheters in human cadavers: where do catheters go?

BACKGROUND Paravertebral regional anaesthesia is used to treat pain after several surgical procedures. This study aimed to improve on our first published ultrasound-guided approach to the paravertebral space (PVS) and to investigate a possible discrepancy between the needle, catheter, and contrast dye position. METHODS In 10 cadavers, we conducted 26 ultrasound-guided paravertebral approaches combined with loss of resistance (LOR) and after an interim analysis performed 36 novel, pure ultrasound-guided (PUSG) paravertebral approaches. Needle-tip position was controlled by a first computed tomography (CT) scan. After placement of the catheters, the tips were assessed by a second CT and the spread of injected contrast dye was assessed by further CT scans. The part of the PVS near the intervertebral foramen was defined as the primary target to reach. RESULTS The first CT scans assessing 62 needle tips revealed that: 13 (50%) of LOR and 34 (94%) of PUSG approaches were at the target; and two (8%) LOR and no PUSG approaches were outside the PVS. With the second CT scans 60 catheter-tip positions were analysed: three (12%) of LOR and five (14%) of PUSG approaches were at the target, three (12%) of LOR and two (6%) of PUSG approaches were outside the PVS. No catheters were detected in the epidural space. In two cases, insertion of the catheter was not possible. In cases with major epidural contrast, the widest contrast dye spread was 7.7 (3.5) [mean (sd)] vertebral segments. CONCLUSIONS Our new PUSG technique has a high success rate for paravertebral needle placement. Although needles were correctly positioned, catheters were usually found distant from the needle-tip position.