Chapter 35: Pectoralis and Serratus Plane Blocks

INTRODUCTION

Pectoralis nerve (Pecs) and serratus plane blocks are newer ultrasound (US)-guided regional anesthesia techniques of the thorax.¹ The increasing use of ultrasonography to identify tissue layers and, particularly, fascial layers has led to the development of several newer interfascial injection techniques for analgesia of the chest and abdominal wall. For instance, the Pecs I block was devised to anesthetize the medial and lateral pectoral nerves, which innervate the pectoralis muscles.¹ This is accomplished by an injection of local anesthetic in the fascial plane between the pectoralis major and minor muscles. The Pecs II block (which also includes the Pecs I block) is an extension that involves a second injection lateral to the Pecs I injection point in the plane between the pectoralis minor and serratus anterior muscles with the intention of providing blockade of the upper intercostal nerves.² A further modification is the serratus plane block, in which local anesthetic is injected between the serratus anterior and latissimus dorsi muscles.³ These interfascial injections were developed as alternatives to thoracic epidural, paravertebral, intercostal, and intrapleural blocks, primarily for analgesia after surgery on the hemithorax. Initially, Pecs blocks were intended for analgesia after breast surgery; however, case reports have also described the use of Pecs and serratus plane blocks for analgesia following thoracotomy⁴ and rib fracture.⁵

Information from the currently published literature on Pecs and serratus plane blocks in peer-reviewed journals is summarized in Table 35–1.^3-8 Pecs blocks have also been proposed in letters to the editor as alternative techniques to anesthetize operative regions such as the axilla, proximal medial upper arm, and posterior shoulder, which are not innervated by the brachial plexus (Figure 35–1).^9,10,11