Erector Spinae Block vs. Placebo Block Study

The ultrasound-guided erector spinae plane (ESP) block has been recently described for the successful management of thoracic neuropathic pain. The erector spinae muscle is formed by the spinalis, longissimus thoracis, and iliocostalis muscles that run vertically in the back. The ESP block is performed by depositing the local anaesthetic in the fascial plane, deep to the erector spinae muscle, at the tip of the transverse process of the vertebra. Indirect access to the paravertebral space is gained providing analgesia without the risk of needle injury to structures in close proximity. Cadaveric studies have shown both ventral and dorsal rami of thoracic spinal nerves are affected when local anaesthetic is injected deep to the erector spinae muscle. The erector spinae muscle extends along the thoracolumbar spine allowing extensive cranio-caudal spread. The ventral ramus (intercostal nerve) is divided into the anterior and lateral branches. Its terminal branches provide the sensory innervation of the entire anterolateral wall. The dorsal ramus is divided into 2 terminal branches and it gives the sensory innervation to the posterior wall. Anterior spread of the local anaesthetic to the paravertebral space through the costotransverse foramina and the intertransverse complex provides both visceral and somatic analgesia. While recent evidence supports statistically significant reductions in pain and opioid consumption among patients who receive an ESP block compared to systemic analgesia alone, the clinical significance of these differences are questionable the effect of ESP block on the patients' quality of recovery following ambulatory breast cancer surgery remains unclear. Therefore, our objective is to determine whether or not the addition of an ESP block provides both superior analgesia and quality of recovery in patients undergoing ambulatory breast cancer surgery compared to systemic analgesia alone. We hypothesis that patients who received a preoperative ESP block will afford superior postoperative analgesia and improve the quality of recovery over the first 24 hours following surgery compared to those who receive a sham block for their ambulatory breast cancer surgery.