Failure of PECS 2 block and a numb hand!!

To the Editor,

A 44 year female with no systemic co-morbidities (American Society of Anesthesiologists'-physical status 1) diagnosed with cystosarcoma phylloides of right breast was posted for a simple mastectomy. It was planned to administer a US guided PECS 2 block as a part of multimodal analgesia along with general anaesthesia using a supraglottic airway. A pre-anaesthesia check up was done. All relevant investigations were normal.

After confirming a 6 hrs nil by mouth status, patient was shifted to the block room. In the block room she received an ultrasound (US) guided PEC 2 block [2 injections- 10 ml of 0.2% ropivacaine between pectoralis major muscle (PMm) and pectoralis minor muscle (Pmm) and 20 ml of 0.2% ropivacaine between Pmm and serratus anterior muscle (SAM)] under due asepsis using a 100 mm stimulating needle (Stimuplex® Ultra 360®, B. Braun Medical Inc).

While wheeling the patient to the operating room, the patient complained of tingling and numbness of fingers of right hand. She was unable to flex and extend elbow, wrist and fingers. After reassuring her, general anaesthesia was induced with 1.5 mg midazolam, 100 μg fentanyl and 200 mg propofol IV. Airway was secured with a 3 sized supraglottic airway (I-Gel).

Intraoperatively, she required a total 200 μg of fentanyl which was suggestive of block failure. During exploration of the axillary fossa the surgeon pointed out towards local anaesthesia collection under a defined sheath [Figure 1]. The operative procedure was uneventful. On postoperative day 2 the right limb did not demonstrate motor power. Tingling and numbness persisted till 5th postoperative day and resolved without any neurological deficit.

Figure 1

Accumulation of local anaesthetic (LA) in axillary fossa after US-guided PECS 2 block. (PECMa- Pectoralis Major muscle, PECMi- PEctoralis minor muscle, LA- local anaesthetic)

Discussion

Blanco[12] described US guided PECS I and 2 block, to provide postoperative analgesia for breast surgery.[12] LA injected in PECS 2 plane involves 20 ml local anaesthetic administration in the plane between SAM and Pmm and another injection between PMm and Pmm. The LA travelled as far as the mid axillary line. Pérez et al. described another technique in which the probe is placed at the outer third of clavicle, the needle is introduced from medial to lateral.[3] However, they did not describe the flow of the LA. A radiological and cadaver study demonstrated the feasibility of anterior approach to serratus anterior interfascial plane and effectively blocking the intercostobrachial nerve and lateral intercostal cutaneous nerves.[4]

In 25 Thiel based cadavers, 10 ml of 0.2% aqueous methylene blue solution was injected from medial to lateral using a single-entry point—triple injection technique.[5] The three subsequent infiltrations were deep to lateral part of the Pmm, between PMm and Pmm, and between PMm and its posterior fascia under US guidance. Upon dissection the lateral and medial pectoral nerves were stained leaving the brachial plexus cords unstained. The study confirmed that 10 ml of solution is sufficient to stain all the medial and lateral pectoral nerve branches without a proximal extension to the cords of the brachial plexus.

In our case the block failed due to spread across components of brachial sheath as LA was seen accumulated in the axillary fossa as a well-defined swelling. The probable reason for early signs of brachial plexus block was action of LA directly on the brachial plexus cords and nerves in the axilla. Since it was a simple mastectomy without axillary clearance the LA accumulation was not drained.

A probable anomalous path might be present which could explain the suspected LA accumulation distal to the site of injection.

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