The pectoral block is a recently developed regional anesthetic technique that can be used for the treatment of postoperative pain after breast surgery. Injection of local anesthetic between the major and the minor pectoral muscles is defined as the pectoral (PEC) 1 block. This block has not been well characterized in terms of its blocking effects on motor and sensitive nerves (medial and lateral pectoral nerves and intercostal nerves). This clinical trial is divided into two sections: a volunteer study and a patient study.

For the volunteer study, the aim is to assess the sensory territory affected by injection of local anesthetics through a PEC 1 block and to assess motor function in terms of strength of adduction of the affected limb using a dynamometer.

In a prospective, randomized, controlled and double blind study, the aim is to assess the postoperative pain relieving properties of the PEC 1 block in patients undergoing bilateral breast augmentation surgery.

Inclusion Criteria:

• breast augmentation surgery
• registration at régie d'assurance maladie du Québec (RAMQ) (social services)

Exclusion Criteria:

• known bleeding disorder
• anticoagulant intake
• infection at site of PEC 1 block
• pregnant or breast-feeding women
• allergy to bupivacaine
• chronic pain including fibromyalgia with regular analgesic consumption
• under recreational drugs or alcohol at doses above canadian recommendations
• muscle relaxants intake
• patients already operated for breast augmentation or mastectomy