PEC’s Block 2018-07-25T00:58:35+00:00

Thoracic paravertebral blocks (TPVB) are widely used regional anaesthetic techniques for breast surgeries. These are technically challenging blocks even under ultrasound guidance and has rare but catastrophic risks like inadvertent entry into the vertebral canal, pneumothorax and spinal cord trauma. Also, TPVB does not provide complete analgesia to the pectoral muscles and skin adjoining the clavicle which are supplied by the brachial plexus (medial and lateral pectoral nerves) and the superficial cervical plexus respectively. Pectoral blocks are alternative to thoracic epidural or paravertebral block to provide analgesia and anaesthesia to hemithorax.

Anatomy

The muscles involved in the pectoral region are Pectoralis Major, Pectoralis Minor, Serratus anterior and Lattisimus Dorsi.

PECTORALIS MAJOR:

ORIGIN: Medial half of clavicle, anterior surface of sternum, first six costal cartilages.

INSERTION: External oblique muscle, lip of bicipital groove of the humerus.

NERVE: Medial and lateral pectoral nerves.

ACTION: Adduction of the extended limb, medial rotation of arm, flexion of upper limb, depression of the arm and shoulder , elevation of the rib.

PECTORALIS MINOR:

ORIGIN:3rd– 5 th ribs, fascia covering intercostal muscles.

INSERTION: Coracoid process of scapula

NERVE: Medial pectoral nerve

ACTION: Depression of the shoulder , draws scapula forward along with serratus anterior.

SERRATUS ANTERIOR:

ORIGIN: First 8 ribs.

INSERION: Inferior angle of scapula(first slip), medial border of scapula (next 3), inferior angle of scapula( Last 4 ).

NERVE: Long thoracic nerve

ACTION: Lateral rotation of scapula.

Nerve supply of the chest wall

  • Brachial plexus: Lateral and medial pectoral nerve arises from lateral and medial cord of brachial plexus respectively. Lateral Pectoral nerve (C5-C7) runs between pectoralis major and minor to supply pectoralis major. Medial pectoral nerve(C8-T1) runs deep to the pectoralis minor to supply pectoralis major and minor.
  • Superficial cervical plexus: Supplies the area of the breast adjacent to the clavicle
  • Thoracic intercostal nerves: Arise from anterior rami of the spinal nerves T1- T11, after emerging from the intervertebral foramen, the nerves travel in the paravertebral space between the parietal pleura and posterior intercostal membrane. The nerves then enter the intercostal space between the innermost and internal intercostal muscles along with the intercostal vessels in the subcostal groove. The intercostal nerves give a lateral branch which pierces the external intercostal and serratus anterior muscles and then divide into the anterior and posterior divisions. Near the sternum, the intercostal nerves pierce the pectoralis major muscle and emerge as the anterior cutaneous branches of thorax.

PEC’s 1 block

PEC I: Technique by which local anaesthetic is injected between the pectoralis major and minor muscles.

Nerves blocked: Medial and lateral pectoral nerves (reduce proprioceptive pain from stretching muscle)

Indications:

  • Subpectoral prosthesis/breast expanders/implant insertion
  • Subpectoral  ICD or pacemaker insertion
  • Adjunct in addition to paravertebral block following mastectomy to improve functional movement of arm and reduce opioid consumption

Scanning technique: 6-13MHz, high frequency linear probe placed below the clavicle in the a superomedial to inferolateral position, probe moved inferolaterally to identify pectoralis major, pectoralis minor and the thoracoacromial vessels in the plane between the muscles.

Dose : 10 mls 0.25% Bupivacaine or 0.2mls/kg of 0.25% Bupivacaine

Needle: 50mm B bevel needle (sufficient in vast majority of cases)

Needling technique: Inplane, cephalad to caudad

Endpoint: Separation of fascial layer between pectoralis major and minor

Surrogate structures: Thoracoacromial vessels help in delineating the plane between the two muscles

Tips: Intramuscular injection is seen as a localised globular spread, interfascial spread is seen as the local anaesthetic splitting the layers and spreading beyond the needle tip.

PECs 1 Block

Ultrasound image of Pecs 1 block

Modified PEC’s 2 block

Modified PEC’s 2: In this block, in addition to PEC’s 1, local anaesthetic is injected in between the pectoralis minor and serratus anterior muscles.

Nerves blocked: Medial and lateral pectoral nerves from PEC’s 1 and lateral branches of intercostal nerves

Indications:

  • Mastectomy with or without reconstruction/subpectoral implant insertion
  • Wide local excision of breast.
  • Sentinel node biopsy.
  • Axillary clearance.
  • Shoulder surgeries (involving armpit)
  • AV fistula formation high up in the arm/armpit

Scanning technique:

Patient in supine position with arm neutral or abducted to 90 degrees. A  6-13 MHz high frequency linear array probe is used and located on mid clavicular level. The probe is moved caudally after identifying axillary vessels and located on 3 – 4 th rib. At this point probe is moved inferolaterally to identify the pectoralis major, pectoralis minor and serratus muscles.

Dose : 20 mls 0.25% Bupivacaine or 0.4mls/kg of 0.25% Bupivacaine

Needle: 50mm B bevel needle (sufficient in vast majority of cases)

Needling technique: Inplane, cephalad to caudad

Endpoint: Separation of fascial layer between pectoralis minor and serratus anterior

Surrogate structures: Gerdy’s ligament, Ribs, pleura

Tips: Interfascial spread is seen as the local anaesthetic splitting the layers and spreading beyond the needle tip.

PEC’s 2 Block

Ultrasound image of Pecs 2 block

Scanning Video for Video PEC’s 1 and 2 Block

Video PEC’s 2 Block

Subpectoral Interfascial Plane Block

Video Subpectoral Interfascial Plane Block