Acoustic puncture assist device™ versus conventional loss of resistance technique for thoracic paravertebral space identification: Clinical and ultrasound evaluation

BACKGROUND: Acoustic puncture assist device (APAD™) is a pressure measurement combined with a related acoustic signal that has been successfully used to facilitate epidural punctures. The principal of loss of resistance (LOR) is similar when performing paravertebral block (PVB). We investigated the usefulness of APAD™ by comparing it with the conventional LOR techniques for identifying paravertebral space (PVS). SUBJECTS AND METHODS: A total of 100 women who were scheduled for elective breast surgery under general anesthesia with PVB were randomized into two equal groups. The first group (APAD group) was scheduled for PVB using APAD™. The second group (C group) was scheduled for PVB using conventional LOR technique. We recorded the success rate assessed by clinical and ultrasound findings, the time required to identify the PVS, the depth of the PVS and the number of attempts. The attending anesthesiologist was also questioned about the usefulness of the acoustic signal for detection of the PVS. RESULTS: The incidence of successful PVB was (49) in APAD group compared to (42) in C group P < 0.05. The time required to do PVB was significantly shorter in APAD group than in C group (3.5 ± 1.35 vs. 4.1 ± 1.42) minutes. Two patients in APAD group needed two or more attempts compared to four patients in C group. The attending anesthesiologist found the acoustic signal valuable in all patients in APAD group. CONCLUSION: Using APAD™ compared to the conventional LOR technique showed a lower failure rate and a shorter time to identify the PVS.