The objective of this study is to assess the non-inferiority of analgesic efficacy of ESP vs PVB for patients undergoing unilateral mastectomy followed by immediate reconstruction.

n breast cancer treatment, surgery plays a central role in combination with chemotherapy, radiation and immunotherapy. Surgery may vary from conservative breast sparing interventions to large radical mastectomies with axillary lymph node dissection that require reconstructive (prosthetic) surgery. In many instances, reconstruction is not performed immediately, but immediate reconstruction is possible and offers many advantages to patients.

The Antoni van Leeuwenhoek hospital performs a large proportion (77%) of mastectomies with immediate reconstruction in the Netherlands. The combination of mastectomy with immediate reconstruction in one operation offers an extra challenge with regards to pain control. Post-operative pain is often treated with opioids, which has systemic side effects (nausea and vomiting). Opioids also inhibit cell-mediated immunity, which is a principal defense against cancer. Regional anesthetic techniques are often performed to reduce opioid consumption and enhance postoperative recovery. The current standard for regional anesthesia for breast surgery is the paravertebral block (PVB). This technique has the potential for severe complications such as epidural hematoma, hemo- or pneumothorax. The erector spinae plane block (ESP) was first described in 2016 as a novel regional anesthetic technique for acute and chronic thoracic pain. The site of injection is distant from the pleura, major blood vessels, and spinal cord; hence, the ESP block has relatively few contraindications and has therefore been suggested as an alternative to PVB when contra-indications, such as a bleeding diathesis, are present.Multiple studies have shown a decrease in opioid consumption in patients undergoing mastectomy, when ESP was compared to placebo. ESP has also been shown to be non-inferior to PVB for pain relief in patients undergoing thoracotomy. To date, only two studies have compared ESP to PVB for breast surgery, with conflicting results. In this study, we would like to investigate whether ESP can be considered non-inferior to PVB with regards to pain relief and use of opioids.

Inclusion Criteria:

• Adult patients (18 years of age or older)
• ASA I-III
• Patients scheduled for elective unilateral mastectomy followed by direct reconstruction
• Ability to give written and oral informed consent

Exclusion Criteria:

• Patient refusal
• Non-elective surgery
• Any contraindication to paravertebral block (including bleeding diathesis, coagulopathy, severe pulmonary disease )
• Allergy to amide-linked local anesthetics
• Cardiac conductivity disorders (e:g: 2nd and 3rd AV-block)
• Severe spinal malformations or history of extensive spine surgery - A history of spinal cord injury
• Known psychiatric disorder
• Chronic pain patients or patients already using opioids pre-operatively
• Infection of the skin at the site of needle puncture area - Inability to give oral and written informed consent

adult female patients