ER-One: A Double-blind Trial of Erector Spinae Block (ESP) Versus Paravertebral Block (PVB) Before Breast Cancer Surgery

The block will be performed with IV Remifentanil sedation Target-Controlled Infusion mode at 2ng/ml and oxygen therapy. For the erector spinae plane block: The puncture will be performed with ultrasound guidance. The ultrasound probe will be placed parallel to the spine parasagittally at the T3 transverse process level. The needle will be introduced and visualized to the plane of the ultrasound image ("in plane"). The desired injection site is between the fascia of the erector muscle of the spine and the transverse process at the T3 level. The operator ensures the correct localization of the needle with saline solution. Then 0.50% Ropivacaine hydrochloride will be injected at a dose of 0.6 ml/kg of actual weight, without exceeding 30 ml. For paravertebral block: The T2 intervertebral space will be located by identifying compared to C7, a prominent cervical vertebra, or by ultrasound by counting the thoracic vertebrae from the first rib. The paravertebral space will be identified by placing the ultrasound probe in a parasagittal or transverse position. The needle will go through the paravertebral muscles and the costo-transverse ligament or by a latero-medial approach using ultrasound. The block will be performed using a 22-gauge 8cm long needle. When the paravertebral space has been reach, an aspiration test will be performed and then 0.6 ml/kg of solution (Ropivacaine hydrochloride solution at 5 mg/ml up to 30 ml) will be injected.