Complication Rate of Ultrasound Guided Paravertebral Block for Breast Surgery
On average one in eight women in the United States will develop breast cancer, with 230,815 new cases in 2013 (most recent CDC data) . Thoracic paravertebral block (TPVB) is a regional technique which has been employed for chest wall and abdominal anesthesia for over 100 years.  The procedure consists of depositing local anesthetic in close proximity to the spinal nerves as they emerge from the intervertebral foramina resulting in ipsilateral blockade of both somatic and sympathetic fibers across multiple dermatomes.  Given the close proximity of the target to the lung, landmark-based techniques have been reported to have pleural puncture rates of 0.5%-1%. The use of ultrasound guidance may provide a reduction of this risk for patients.
Material and methods:
This was a retrospective cohort study of patients who received ultrasound guided paravertebral blocks over a four year period during which all patients received post-operative chest X-rays. This study was conducted with a retrospective study waiver from the Mayo Clinic IRB and utilized the Mayo Clinic ChartPlus anesthesia electronic environment OR Datamart. Two independent reviewers abstracted data including: age, type of procedure, inclusion of axillary dissection, total number of levels blocked, needle type used, local anesthetic volume and concentration, epinephrine premix, inclusion of clonidine or dexamethasone, block time, recorded pleural puncture, recorded pneumothorax, pneumothorax on post-operative chest X-ray, length of Post Anesthesia Care Unit stay, unplanned admission, and increases of heart rate or mean blood pressure within 15 minutes of block end time.
556 patients were included in this study, with a median of four block levels per patient and a range of 1 to 12 levels for a total number of levels blocked of 2244. 31.1% of procedures were unilateral mastectomies without reconstruction, 28.6 percent were bilateral without reconstruction, 16% were unilateral with reconstruction, and 23.7% were bilateral with reconstruction. 54.3% of patients received sentinel node biopsy, 30% progressed to axillary dissection, and 15.7% had no axillary procedure. The most common needle used was an insulated 21 gauge 4 inch needle at 85.4%. Epinephrine was included in 74% of injections. No pleural punctures were noted, two instances of pneumothorax were identified by post-operative Chest X-ray.
Thoracic paravertebral blockade provides a safe and reliable anesthetic state for mastectomy. This study is novel as we obtained a chest radiograph of every patient following surgery. Similar to previous studies, no pleural punctures were noted while performing a block, but two pneumothoraxes were diagnosed on post-operative chest radiograph. This leads to a pneumothorax rate of 0.9 per 1,000 blocks.