Purpose: Regional anesthesia has been shown to improve outcomes in several recent studies. The transversus abdominis plane (TAP) block provides anesthesia to the abdominal wall by introducing local anesthetic to the ventral rami of the thoracolumbar nerves. This work quantifies the area of anesthesia obtained after performing the novel thoracolumbar interfascial plane block (analogous to the TAP block but intended for the back) which targets the sensory component of the dorsal rami of the thoracolumbar nerves.
Methods: Ten participants underwent bilateral ultrasound-guided injections of 0.2% ropivacaine 20 mL into the fascial plane between the multifidus and longissimus muscles. After five and 20 min, respectively, the area of anesthesia was plotted on the participant's back. Anesthesia was defined as loss of point discrimination to pinprick.
Results: Participants reported a mean (SD) area of anesthesia surrounding the needle injection site of 137.4 (71.0) cm(2) and 217.0 (84.7) cm(2) at five and 20 min after injection, respectively. The mean (SD) cephalad and caudal spread of local anesthetic from the site of injection was 6.5 (1.8) cm and 3.9 (1.2) cm, respectively. There were no complications or adverse events reported.
Conclusion: This report shows that a reproducible area of anesthesia can be obtained by ultrasound-guided injection of local anesthetic in the fascial plane between the multifidus and longissimus muscles of the thoracolumbar spine. The area of anesthesia consistently covered the midline and had a predictable spread. This project was registered with clinicaltrials.gov (NCT02297191).