In breast surgery, field block infiltration or fascial plane infiltration can be an effective technique in a multimodal analgesia strategy1,2

A PECS (ultrasound-guided medial and lateral pectoralis nerve) block is a less invasive technique for providing analgesia after breast surgery compared with standard approaches such as thoracic epidural, paravertebral, intercostal nerve, and interpleural blocks.2,3

PECS blocks are applied in the pectoral and axillary regions, with the muscles in both regions innervated by the brachial plexus.3

In PECS I and PECS II field infiltration, ultrasound guidance can be used to identify the appropriate fascial plane(s) and to deposit local anesthetic to provide regional analgesia.2

These techniques provide effective analgesia after breast surgery and, unlike thoracic paravertebral and epidural blocks, are not associated with sympathetic blocks.2

PECS blocks can be administered by the anesthesiologist or surgeon;
direct injection during open surgery is also possible2

Areas covered by a PECS I or PECS II block

Interior View

External anterior view of areas covered by PECS I and PECS II block

PECS I block3 (red area)Devised to anesthetize the medial and lateral pectoral nerves, which innervate the pectoralis muscles

  • Supraclavicular nerves
  • PECS II block3 (light blue area)Extends the block to provide blockade of the upper intercostal nerves

  • Anterior cutaneous nerve
  • Lateral cutaneous nerve

Consider the neuroanatomy to target the appropriate nerves for a PECS block

Interior View

Interior view of nerves to target with a PECS block

PECS I block2The lateral and medial pectoral nerves lie in the fascial plane between the pectoralis major and minor muscles

PECS II block2Spinal nerves T2-T4 lie in the fascial plane between the pectoralis minor and serratus anterior muscles

  • Dorsal nerve
  • Anterior scalene muscle
  • Brachial plexus
  • Axillary artery
  • Medial pectoral nerve
  • Lateral pectoral nerve
  • Musculocutaneous nerve
  • Thoracodorsal nerve
  • Latissimus dorsi muscle
  • Long thoracic nerve

Internal sagittal view of where to inject local anesthetic

PECS I block2Injection between pectoralis major and minor muscles

  • Pectoralis major
  • Pectoralis minor
  • Serratus anterior
  • Rib 4
  • Rib 3
  • PECS II block2Injection between the pectoralis muscles and a second injection between the serratus anterior and pectoralis minor muscles

  • Rib 2
  • Rib 1
  • Coracoid process
  • Clavicle