Presented at the 2012 AAPM Annual Meeting « Back

Ultrasound-Guided Paravertebral Injection Spread Patterns: A Cadaveric Imaging Study

Adam Wallace, MD, wallace.adam@mayo.edu¹, Joseph A. Cartwright, MD¹, James C. Watson, Board Certified Neurologist², Susan M. Moeschler, MD², (1) Mayo Clinic, Jacksonville, Florida, (2) Mayo Clinic, Rochester, Minnesota

Introduction: Paravertebral blocks (PVB) are frequently performed in the perioperative setting for analgesia following breast, thoracic, and abdominal surgery as well as a diagnostic and therapeutic intervention for chronic pain. The ultrasound-guided PVB has been well described (1). However, oftentimes the volume injected is arbitrary. Studies have been done to determine the spread of contrast following ultrasound-guided PVB injections in regard to local coverage of nerve roots (2-3), however, further radiographic imaging has not been described. Materials and Methods: After IRB approval, two fresh frozen cadaver torsos were obtained for study use. The paravertebral space was identified via ultrasound examination on each cadaver, bilaterally, using a Phillips CX50 12 MHz linear array probe. Under ultrasound visualization, the paravertebral space was identified in the thoracic spine in each cadaver and assigned volumes of iohexol contrast were injected utilizing a 22-gauge spinal needle. Subsequently, a Phillips MD Allura 3DRA fluoroscope was used to obtain a three-dimensional (3-D) reconstruction of the anatomy and spread pattern of contrast after each injection. Results: Fluoroscopy with 3-D reconstruction revealed a correct paravertebral spread of contrast during each injection. However, there was much more significant intercostal and epidural spread of contrast at even relatively low volume (5cc) injections than anticipated. Conclusions: Paravertebral spread of contrast is highly variable with intercostal and epidural spread over a range of volumes. These distant spread patterns illustrate why patients may not have uniform dermatomal coverage and why providers must remain vigilant after PVB. References: 1)O Riain, SC, et al., Thoracic paravertebral block using real-time ultrasound guidance. Anesth Analg. 110(1): p. 248-51. 2)Cowie, B., et al., Ultrasound-guided thoracic paravertebral blockade: a cadaveric study. Anesth Analg. 110(6): p. 1735-9. 3)Paraskeuopoulos, T., et al., Thoracic paravertebral spread using two different ultrasound-guided intercostal injection techniques in human cadavers. Clin Anat. 4)Ben-Ari, A., et al., Ultrasound-guided paravertebral block using an intercostal approach. Anesth Analg, 2009. 109(5): p. 1691-4. 5)Kairaluoma, P.M., et al., Single-injection paravertebral block before general anesthesia enhances analgesia after breast cancer surgery with and without associated lymph node biopsy. Anesth Analg, 2004. 99(6): p. 1837-43. 6)Pintaric, T.S., et al., Comparison of continuous thoracic epidural with paravertebral block on perioperative analgesia and hemodynamic stability in patients having open lung surgery. Reg Anesth Pain Med. 36(3): p. 256-60. 7)Eason, M.J. and R. Wyatt, Paravertebral thoracic block-a reappraisal. Anaesthesia, 1979. 34(7): p. 638-42. 8)Gerner, P., Postthoracotomy pain management problems. Anesthesiol Clin, 2008. 26(2): p. 355-67, vii. 9)Bondar, A., S. Szucs, and G. Iohom, Thoracic paravertebral blockade. Med Ultrason. 12(3): p. 223-7.

Funding: None