OriginalUltrasound description of Pecs II (modified Pecs I): A novel approach to breast surgeryDescripción de la ecografía de los pectorales II (pectorales I modificados): un nuevo enfoque de la cirugía mamaria
Introduction
The neural supply of the anatomical structures involved in breast surgery is not well understood when it comes to providing analgesia for perioperative pain relief. Thoracic epidural1 and paravertebral2, 3, 4 blocks became the gold standard techniques to achieve this goal, but not every anesthesiologist is comfortable performing these procedures. As an alternative for these techniques we designed a novel series of blocks: Pecs I and Pecs II.
The Pecs block type I5, 6, 7 is a recently described, easy and reliable superficial block that targets the lateral and median pectoral nerves at an interfascial plane between the pectoralis major (PMm) and minor (Pmm) muscles. It can be used for different breast operations, but we mainly use it for the insertion of breast expanders and subpectoral prosthesis. Other potential indications are traumatic chest injuries, iatrogenic pectoral muscle dissections, pacemakers, Port-a-caths and chest drains.
In this paper we describe a second version of the Pecs block type I. We call it “modified Pecs's block” or Pecs block type II. This novel approach aims to block the axilla that is vital for axillary clearances and the intercostal nerves, necessary for wide excisions, tumorectomy, sentinel node exeresis and several types of mastectomies.
To perform the Pecs II block or “modified Pecs's block” we use two needle approaches instead of one. The first puncture is a Pecs I block with 10 ml of local anesthetic injected between the pectoralis muscles, and the second puncture gives 20 ml of local anesthetic between the Pmm and the serratus muscle. This will break through the ‘axillary door’ and will reach the long thoracic nerve and reliably at least two intercostal nerves. We designed this block because, although during breast expander and subpectoral prosthesis insertions the PMm is mainly affected, there is still significant pain reported over the serratus muscle area. The Pecs II aims to block this region, together with the lateral branches of the intercostal nerves that exit at the level of the mid-axillary line to innervate the mammary gland and the skin from T2 to T6.
To understand the theory and practice of the Pecs blocks we must first make a detailed review of the anatomy involved in this region. The pectoral nerves are major nerves arising from the brachial plexus innervating the pectoral muscles. The lateral pectoral nerve most commonly arises from C5, C6 and C7, and the median pectoral nerve from C8 and T1.The lateral pectoral nerve is the bigger of the two and runs between the major and minor pectoral muscles in a fascial plane in close proximity to the pectoral branch of the thoracoacromial artery and innervates the PMm.
The medial pectoral nerve runs under the Pmm. It crosses the muscle to reach the lower third of the PMm in the pectoral region after piercing the two layers of the clavipectoral fascia. Various groups agree that the medial pectoral nerve crosses Pmm in 62% of the patients, while in the remainder it is located on its lateral border.8
A second set of nerves involved are the anterior divisions of the thoracic intercostal nerves from T2 to T6. They lie at the back between the pleura and the posterior intercostal membrane and run in a plane between the intercostal muscles as far as the sternum. The intercostal nerves give off lateral and anterior branches. Lateral branches: the nerves pierce the intercostalis externi and the serratus anterior muscles at the mid-axillary line to give off anterior and posterior terminal branches. The lateral cutaneous branch of the second intercostal nerve does not divide in anterior and posterior branches and it is called the intercostobrachialis nerve. Anterior branches: the nerves cross in front of the internal mammary artery, pierce the intercostalis interni muscle, the intercostal membranes and PMm to supply the breast in its medial aspect.
Finally a third group of nerves needs to be taken into account: these are the long thoracic and the thoracodorsal nerve. The long thoracic nerve or serratus anterior nerve arises from C5 to C7 entering the axilla behind the rest of the brachial plexus and resting on the serratus anterior muscle. It supplies this muscle, and when it is damaged by axillary clearances or radical mastectomies produces a winging scapula, especially when the arm is lifted forward. During surgery the serratus muscle is dissected together with the pectoralis muscles to make the pocket needed for breast expanders.
The thoracodorsal nerve is a branch of the posterior cord made up of the three posterior divisions of the trunks of the brachial plexus. It follows the thoracodorsal artery and innervates the latissimus dorsi in the posterior wall of the axilla. It lies very deep, and it is important during latissimus dorsi flaps for breast reconstructions.
To complete the knowledge of the axillary and breast region we need to mention two other structures involved in these blocks: the clavipectoral fascia and Gerdy's ligament. The fascia on the superficial surface of Pmm is the clavipectoral fascia and the hard fascia on the lateral border is Gerdy's ligament or suspensory ligament of the axilla, which is a connective tissue that maintains the concave shape of the axilla. We can see the anatomical relationship of the structures involved in Figure 1.
The Pecs II block is a simple alternative to the conventional paravertebral and neuroaxial blocks for breast surgery. The block produces excellent analgesia and can be used to provide a balanced anesthesia and as a rescue block in cases where the analgesia provided by the paravertebral or epidural was patchy or ineffective. In our opinion, the easily identifiable landmarks make this block a good novel regional anesthetic technique.
Section snippets
Description of the block sequence
It is our practice to perform Pecs I for operations where expanders are inserted during breast reconstruction. We choose Pecs II for the same operation when axillary clearances are required or for the rest of glandular operations involving intercostal innervations. Informed consent for the block was requested, together with consent for general anesthesia or deep sedation. An IV access is also inserted for monitoring. The infraclavicular and axillary regions were cleaned with chlorhexidine. The
Results and discussion
The analgesia for breast reconstructive surgery can involve different degrees of nerve blocks, so we have described different types of modifications to suit the type of surgery depending on the affected tissues and nerves (Pecs I and Pecs II or modified Pecs). During breast expanders and prosthesis insertions the PMm is mainly involved. For tumorectomies, mastectomies and sentinel node dissection, the intercostal nerves are the main nervous structures that we need to block. And, finally, for
Conflict of interest
The authors declare no conflicts of interest.
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