Thoracic Paravertebral Block Anesthesia for Breast Cancer Surgery: Single-Injection Versus Multiple Injections. A Randomized Controlled Trial

Breast cancer is the most common cancer among women representing around 25% of new cancer cases worldwide. Surgery is the mainstay of treatment. Mastectomies are usually performed under general anesthesia (GA), often with the addition of regional anesthesia for post-operative pain relief. TPVB have previously been described in the literature to be sufficient for intra-operative anesthesia as an alternative to GA. This technique was first developed by Sellheim in 1905, and was popularized by Eason and Wyatt in 1978. In recent years, there has been a regain of interest for this technique with the easier access to high-performance ultrasound. The thoracic paravertebral space is a wedged shaped space adjacent to the spine bilaterally. It is a continuous space filled with adipose tissue that communicates cranially and caudally. TPVB produce unilateral, segmental, sympathetic and somatic blockade of the chest. Landmark-based techniques were first described, but in recent years ultrasound-guided techniques have been shown to improve the success rate of the block. They can be performed through multiple injections at different thoracic levels or with a single injection. Mutiple injections offer many advantages including coverage for each dermatome associated to the blocked level. Whereas blockade of multiple contiguous levels when performing a single injection implies relying on the spread of local anesthetic (LA) to caudal and cranial levels to block more dermatomes. Some studies have demonstrated that single-injection paravertebral blocks at the level of T3-T4 could be a suitable alternative to general anesthesia, but the blocks were not done under ultrasound guidance and they did not compare the single-injection technique to the multiple injection technique. Thus, a randomized controlled trial comparing the single-injection TPVB technique to the multiple injection technique done under ultrasound guidance for breast cancer surgery anesthesia is needed. The single-injection technique would allow us to offer the TPVB benefits to our patients while decreasing the time to perform the block, the complication rate and therefore potentially improve patient satisfaction.

Our hypothesis is that the TPVB performed as a single injection is non inferior to multiple (three) injections for unilateral oncologic breast surgery without axillary intervention.

The current study is a prospective randomized controlled trial of patients undergoing oncologic breast surgery without axillary node dissection or immediate reconstruction. Patients will be randomized into two groups; thoracic paravertebral block (TPVB) single-injection or TPVB multiple (three) injections. Sedation and analgesia will be standardized for both groups. The block will be performed preemptively by a blinded anesthesiologist at least 20 minutes before surgical incision. 30 milliliters (ml) of ropivacaine 0.5% will be injected on the operating side (maximum 3 milligrams per kilograms (mg/kg)) either as a single injection or fractionated into three injections at three different paravertebral levels.

Preemptive postoperative analgesia plan:

• Each patient will receive standard preemptive postoperative analgesic medication comprising of oral acetaminophen 1 gram (g) preoperatively