Combined transverse thoracis plane and pectoral nerve blocks for breast surgery under sedation

Summary

The pectoral nerves 2 (pecs 2) block is widely used as adjunct to general anaesthesia for breast surgery. There are a few case reports and a single case series that describe regional anaesthesia as a single technique or supplemented by light to moderate sedation. Here we describe the management of a 91‐year‐old ASA physical status 4 patient who presented with a T4 breast malignancy. She was considered unfit for general anaesthesia due to significant valvular heart disease. A wide local excision was successfully performed under a pecs 2 block and a transverse thoracis plane block, supplemented with light sedation. We consider this technique to be a good option for selected patients who are considered unfit for general anaesthesia.

Introduction

Regional anaesthesia has been widely used as an adjunct to general anaesthesia for breast surgery since Blanco introduced the pectoral nerves (pecs) block in 2011 and the pecs 2 block in 2012 [1]. In breast surgery, the pecs 2 block decreases postoperative pain, opioid consumption and postoperative nausea and vomiting [2, 3]. Several studies have shown that adding a transverse thoracis plane (TTP) block or parasternal block decreases postoperative pain scores after breast surgery even further [4, 5]. Instead of supplementing general anaesthesia, there are a few case reports suggesting that breast surgery might be possible with regional anaesthesia in isolation or supplemented by sedation [6, 7, 8]. Additionally, Pawa et al. published a case series of 16 breast cancer operations performed under thoracic paravertebral block, pectoral nerves block and sedation [9]. In this case report, we describe the anaesthetic management of a patient requiring wide local excision of a T4 breast cancer who was considered unfit for general anaesthesia.

Report

A 91‐year‐old, ASA physical status 4 woman with Alzheimer’s disease was diagnosed with a left‐sided breast cancer in 2018. The patient declined treatment at that time. She had a medical history of moderate dementia, hypertension, stroke, complete heart block treated with a dual chamber pacemaker and asymptomatic aortic stenosis. Two years later, the tumour had grown and was clinically graded as T4, compromising the skin. To prevent ulceration and achieve local control of disease, a wide local excision of the tumour was proposed without treatment of the axilla or subsequent adjuvant radiotherapy.

We considered the patient unfit for general anaesthesia primarily due to her cardiac pathology. Pre‐operative screening with transthoracic echocardiography showed severe aortic stenosis (maximum velocity = 4.4 m.s⁻¹), severe concentric left ventricular hypertrophy, normal left ventricular ejection fraction and rheumatic mitral valve disease with mild to moderate stenosis and moderate insufficiency.

Regional anaesthesia as a single technique was discussed with the patient, her daughter (medical power of attorney) and the surgeon. All agreed with the plan to perform the surgery under a pecs 2 block in combination with a TTP block.

No sedation was used when performing the blocks, and no local anaesthesia was used to anaesthetise the skin. We used a three‐way connector on the needle (Pajunk SonoPlex 22G × 50 mm, Pajunk GmbH Medizintechnologie, Geisingen, Germany) to localise the correct tissue planes with saline 0.9%. This ensured optimal deposition of local anaesthetic in the desired plane. Pecs 2 block was performed according to the technique described by Blanco et al. [2]. At the level of the third rib, we sonographically localised the pectoralis major and minor muscles and the pectoral branch of the thoraco‐acromial artery interposed between them, where we injected 10 ml of ropivacaine 0.375%. We then advanced the needle to the plane between the pectoralis minor muscle and the serratus anterior muscle and deposited 15 ml ropivacaine 0.375%. We then performed an ultrasound‐guided TTP block at the level of the third intercostal space using a parasagittal, in‐plane needle approach. When the transverse thoracis muscle and intercostal muscle were visualised, 10 ml of ropivacaine 0.375% was deposited in between them. We examined the extent of the sensory block 45 minutes later with ice (Fig. 1).

Figure 1.

Area insensitive to cold as reported by the patient (black outline). The finger lifting the breast is positioned on the tumour.

Because the patient was slightly confused and restless, we sedated her with 1.5 mg of midazolam. Surgery was painless until the surgeon handled the medial caudal aspect. An attempt to anaesthetise this area with 5 ml of lidocaine 0.5% and adrenaline 2.5 μg.ml⁻¹ was insufficient. We therefore commenced remifentanil at 0.1 μg.kg⁻¹.min⁻¹. This was sufficient to continue surgery. The surgeon also switched from electrocautery to using a scalpel, which resulted in complete resolution of discomfort, after which we ceased the remifentanil infusion. The operation took 30 min with remifentanil required for 10 min of this time. The patient was then discharged to the postanaesthetic care unit with a numeric rating scale score of 0 out of 10 and was discharged from hospital the same day. The excised tissue measured 18 × 11 cm and the pathology report demonstrated that an adequate radical resection had been performed. No wound complications or additional cognitive decline occurred after discharge.

Discussion

The use of regional anaesthesia as a single technique for breast surgery has previously been described [6, 7, 8, 9]. Case reports and a single case series show that sedation and/or additional local anaesthetic infiltrated by the surgeon is often necessary if surgery is more extensive. The reason for this is not clear.

Considering the innervation of the breast, the choice of regional anaesthesia must be carefully selected. The pectoral muscles are innervated by the medial and lateral pectoral nerves originating from the brachial plexus. More superficial structures (breast tissue and skin) on the lateral side of the breast are innervated by the lateral branches of the third to sixth thoracic intercostal nerves. The medial side of the breast is innervated by the medial branches of the second to sixth thoracic intercostal nerves. The skin of the cranial part of the breast is innervated by supraclavicular nerves originating from the superficial cervical plexus. Cadaver studies suggest that the role of the supraclavicular nerves is limited to the area immediately caudal to the clavicle [10]. Therefore, it is unlikely that anaesthetising these nerves is necessary for breast surgery. The long thoracic nerve, intercostobrachial nerve and medial brachial cutaneous nerve play an important role in the innervation of the axilla.

A pecs 2 block provides sufficient anaesthesia for lateral breast surgery and/or axillary lymph node dissection. Adding a TTP block, parasternal block, paravertebral block or epidural anaesthesia is necessary for any type of surgery where the medial side of the breast is involved (medial lumpectomy; surgery around the nipple; or mastectomy). A single paravertebral or epidural block is not sufficient for all types of breast surgery because neither technique anaesthetises the medial and lateral pectoral nerves, nor do they block the long thoracic nerve or the medial brachial cutaneous nerve. Key benefits of the TTP block over a thoracic epidural are elimination of the risks of hypotension, sympathectomy or dural puncture. It is superior to a thoracic paravertebral block because there is less chance of pneumothorax, vascular puncture, hypotension and no risk of epidural or intrathecal spread. It is also an attractive option for patients of low body weight, because a lower volume of local anaesthetic is needed for a TTP block when compared with a paravertebral block. Lastly, the concomitant administration of anticoagulant therapy poses a reduced risk than an epidural and thoracic paravertebral block.

In the reported case, pain was felt in an area which was tested pre‐operatively and considered anaesthetised, requiring additional sedation. The cause of this is interesting to evaluate. Firstly, surgical pain despite an adequate block can be due to traction on tissue outside of the anaesthetised area with forceps. Another explanation is the use of electrocautery which may lead to stimulation of nociceptors further away from the surgical field due to tissue conduction of residual current. Pain sensation can therefore extend beyond the anaesthetised area. Using a scalpel for the outer areas of the surgical field could be an effective way to minimise pain, as it was in our case. We hypothesise that remifentanil might not have been necessary if the use of electrocautery was minimised. The postoperative numeric rating scale score of 0/10 confirms that our blocks covered the entire surgical field. A third explanation might the lower concentration of ropivacaine used. This diluted concentration was necessary due to low patient weight and a high‐volume local anaesthetic needed for three blocks. Before performing the blocks, we considered the maximal non‐toxic ropivacaine dose to be 3 mg.kg^‐1. The patient weighed 50 kg, so the maximum allowed dose was 150 mg. With ropivacaine 0.375% (3.75 mg.ml^‐1) we were able to use 35 ml for the blocks. This is 87.5% of the maximal non‐toxic local anaesthetic dose. The remaining 12.5% could be used by the surgeon as a supplement during surgery. We chose lidocaine 0.5% (5 mg.ml^‐1) with adrenaline 2.5 μg.ml^‐1 for this because it is rapid acting and has modest systemic absorption. The maximal calculated dose for the surgeon to use was derived as:

$$\text{Maximal allowed volume}\left(\text{ml}\right)=\text{maximum dose of lidocaine with adrenaline}\left(\text{mg}.{\text{kg}}^{‐1}\right)\times \text{total body weight}\left(\text{kg}\right)\times \text{proportion of maximum local anaesthetic dose remaining / concentration of lidocaine used}\left(\text{mg}.{\text{ml}}^{‐1}\right)$$

$$\therefore \text{Maximal allowed volume}\left(\text{ml}\right)=7\text{mg}.{\text{kg}}^{‐1}\times 50\text{kg}\times \mathrm{0.125/5}\text{mg.ml}=8.5\text{ml}$$

In our routine practice, ropivacaine 3.75 mg.ml⁻¹ seems to be an adequate concentration for surgery. In this case however, it could have been a reason why our patient experienced pain. A fourth explanation might be that our blocks did not provide enough anaesthesia in the caudal margin of the breast due to how we divided our local anaesthetic volume. Theoretically, a pecs 1 block should not require a large volume due to the close proximity of the medial and lateral pectoral nerve to the pectoral branchs of the thoraco‐acromial artery, which is often viewed on ultrasound. This in contrast to a pecs 2 or TTP block, which need more volume to reach distant nerve branches. It is worthwhile to consider using less volume for pecs 1 and using more volume for the pecs 2 and TTP components, or to perform a multilevel TTP block. In general, differing results of regional anaesthesia (and therefore the need for sedation and/or additional local anaesthetic) can be explained by different surgical and anaesthetic techniques and interindividual anatomical variation in patients [10].

This case report shows that extensive breast surgery is possible with the combination of a pecs 2 block and a TTP block, supplemented with light to moderate sedation. We consider it to be a good alternative for patients with a contra‐indication to general anaesthesia due to severe pulmonary or cardiac comorbidities. It is also a suitable alternative to the combination of a pecs 2 block and an epidural or thoracic paravertebral block.