Ultrasound‐guided sacral multifidus plane block for analgesia following excision of sacrococcygeal teratoma in two neonates

Summary

Peri‐operative pain management in the neonate with a sacrococcygeal teratoma poses significant challenges to the anaesthetist. Involvement of the sacrococcygeal area by the tumour often prevents the use of conventional regional anaesthetic techniques such as caudal or epidural analgesia, with a subsequent reliance on intravenous opioids and paracetamol. Since opioids are associated with respiratory depression, constipation and urinary retention, there is high incidence of opiophobia with consequent inappropriate dosage prescription, particularly in the paediatric population. We describe the use of an ultrasound‐guided sacral multifidus plane block in two neonates undergoing surgical excision of sacrococcygeal teratoma. The block is technically easy to perform and also avoids traversing critical structures. Hence, it may be regarded as a promising analgesic technique for painful interventions in the sacrococcygeal area.

Introduction

Sacrococcygeal teratomas are the most common congenital neoplasms, with an incidence of 1 in 30,000–40,000 live births with female preponderance [1]. Both anaesthetic management and surgery for sacrococcygeal teratomas may prove to be challenging. Commonly used regional anaesthetic techniques such as caudal or epidural anaesthesia are not possible due to involvement of the coccyx and sacrococcygeal junction by the tumour [1].

The erector spinae plane block, which involves deposition of local anaesthetic in the fascial plane between the erector spinae muscles and the transverse process, has been used successfully to provide postoperative analgesia in thoracic, abdominal and lower extremity surgical procedures in children [2]. Recently, another paraspinal fascial plane block, the sacral multifidus plane block, which targets the fascial plane underneath sacral multifidus muscle, has been reportedly used successfully in infants [3, 4]. We present two cases of successful ultrasound‐guided sacral multifidus plane block for postoperative analgesia following surgical excision of Altman type 1 sacrococcygeal teratomas, which are predominantly external with a minimal presacral component, in two otherwise healthy neonates delivered by caesarean section.

Report

Patient 1

A 4‐day‐old, 2.7‐kg girl born at full term presented for resection of a 4 × 5 cm sacrococcygeal teratoma. Under standard monitoring, general anaesthesia was induced with intravenous (i.v.) fentanyl and propofol. Atracurium was administered to facilitate tracheal intubation. General anaesthesia was maintained with isoflurane in an oxygen/nitrous oxide mixture.

The child was turned prone and the sacral area was prepared and draped. A 5–13 MHz high frequency linear probe (DC‐70 series, Mindray Medical International Company Ltd., Shenzhen, China) was placed in the midline just above the sacrum. The transducer was then slid caudally to delineate the second and third median sacral crests, as described by Tulgar et al. [5]. Thereafter, the transducer was rotated 90° to obtain a transverse view of the sacrum which showed the multifidus muscle with overlying erector spinae aponeurosis (Fig. 1). Using an in‐plane approach, a 22‐gauge, 50‐mm needle was then advanced from lateral to medial, targeting the fascial plane between the multifidus muscle and the median sacral crests of S2 and S3. Following negative aspiration, a mixture of 0.9 ml bupivacaine 0.25% and dexamethasone 0.125 mg was injected. The same procedure was performed contralaterally. Intravenous paracetamol 10 ml.kg^‐1 was administered before the end of surgery. The patient was transferred to the neonatal high dependency care unit for observation.

Figure 1.

Showing (a) Sono‐anatomy of sacral multifidus plane and administration of the anaesthetic drug at S2/S3 level. Arrow denotes the needle; ESA, erector spinae aponeurosis; MC, median sacral crest MF, multifidus muscle; LA, local anaesthetic. (b) Posterior and lateral view of sacrum showing median sacral crest and intermediate sacral crest with attachment of multifidus and erector spinae aponeurosis. ESA denotes erector spinae aponeurosis; IC, intermediate sacral crest; MC, median sacral crest; MF, multifidus muscle. (c) Organization of the posterior lumbar and sacral musculature showing the iliocostalis, the longissimus, the lumbar multifidus and, the sacral multifidus. IC denotes intermediate sacral crest; IL, iliocostalis; LG, longissimus; L‐MF, lumbar multifidus; MC, median sacral crest; S‐MF, sacral multifidus.

Postoperatively, pain was assessed using facial expression, legs, activity, crying and consolability (FLACC) score at regular intervals [5] The FLACC score immediately postoperative was zero. The time to administration of first rescue analgesia was 14 h at which time a FLACC score of four was recorded. The patient had an uneventful recovery and was discharged from the hospital on the eighth postoperative day without any complications.

Patient 2

A 3‐day‐old, 3.2‐kg girl born at a gestational age of 36 weeks presented for resection of 6 cm x 4 cm sacrococcygeal teratoma. Anaesthesia management and ultrasound‐guided sacral multifidus plane block procedures were performed as described in the previous case. A mixture of 1 ml bupivacaine 0.25% with dexamethasone 0.125 mg was administered in the fascial plane beneath the sacral multifidus muscle on either side of the median sacral crest. Postoperatively, the patient had a FLACC score of one, and time to first rescue analgesia was 11 h with a FLACC score of four recorded at that time. The patient had an uneventful recovery and was discharged from the hospital on the eighth postoperative day without any complications.

Discussion

Sacrococcygeal teratomas are the commonest primordial germ cell tumours, arising from the base of the coccyx. They may grow in a posterior direction forming an external protrusion, or in the anterior direction, dissecting and distorting surrounding pelvic structures and with the potential to invade the spinal cord [1, 6]. Involvement of coccyx and sacrococcygeal junction by sacrococcygeal teratomas makes the administration of caudal analgesia virtually impossible, thus depriving these neonates of the benefits of regional analgesia.

Tulgar et al. described the first successful sacral multifidus plane block in a young man undergoing surgery for pilonidal cyst. They reported satisfactory analgesia for 13 h with deposition of bupivacaine deep to the multifidus muscle lying posterior to the sacrum between the median and intermediate sacral crest [7]. Since then, few other cases have been reported in literature [3, 4, 8]. However, in some initial reports, sacral multifidus plane block was referred to as an ‘erector spinae plane block’ incorrectly, as some authors use this term to refer to all blocks targeting the intrinsic back muscles and because anatomy studies and atlases often depict the paraspinal muscles as a single mass in cross section. Hamilton et al. challenged this nomenclature and emphasised that transversospinales muscle group differed from the erector spinae muscle group and hence the sacral erector spinae plane block should be actually referred to as the sacral multifidus plane block in line with correct anatomical terminology [8].

Anatomically, the major muscle groups of the lumbar spine can be divided into anterior (hypaxial) and posterior (epaxial) groups based on an imaginary coronal plane that passes through the transverse processes. The epaxial group is formed by two major muscle groups: (1) the erector spinae muscle group (consisting of longissimus and iliocostalis laterally); and (2) the transversospinales muscle group (consisting of multifidus, semispinalis and rotatores medially). The thick erector spinae aponeurosis extends from the thoracic region to the sacrum and covers the lumbar erector spinae muscle group.

At the level of the lumbosacral junction the longissimus and iliocostalis bellies disappear, ending their attachments on the ilium and the sacrum. The multifidus expands in width and bulk in a caudal direction and forms the dominant paraspinal muscle in the sacral area. The multifidus is covered by the erector spinae aponeurosis, from which it is separated by a cleavage plane. The dorsal branches of the sacral nerves exit from the posterior sacral foramina and course along the posterior aspect of the sacrum, pass through the multifidus muscle, and divide into the medial and lateral branches. The medial branches end in the multifidus, whereas the lateral branches join and advance superficially to the skin. They supply the sensory innervations of the posterior part of the buttock and gluteal area and are an important neural target of the sacral multifidus plane block [9].

Previously, the use of the sacral multifidus plane block has been described only in two paediatric patients, using 1 ml.kg^‐1of bupivacaine 0.25%, with no requirement for rescue analgesia until 24 h after surgery. However, we used a lower volume of local anaesthetic in our patients. This is based on previous experiences of the erector spinae plane block in paediatric patients, where a volume of 0.5–0.6 ml.kg^‐1 of local anaesthetic ensures a spread over at least five dermatomes, suggesting that at least 0.1 ml.kg^‐1 of local anaesthetic is required per dermatome in infants and toddlers [2]. This is also supported recent guidelines for local anaesthesia in paediatric regional anaesthesia [10].

Neither of our patients developed any motor weakness, urinary retention or constipation. This may be due to the confined spread of the low volumes of local anaesthetic to the sacral multifidus muscle by the erector spinae aponeurosis, such that only the dorsal rami were involved, while sparing the anterior branches of sacral nerves or sacral plexus. Cranial spread to the lumbar dermatomes may have been limited by the iliolumbar ligament [2, 9].

This block is administered in close proximity to the lesion with possible underlying anatomical distortion and this may present some challenges. Although rare, sacrococcygeal tumours can invade and involve the spinal cord and neighbouring nerve roots directly and can present with a range of neurological symptoms. Spinal ultrasonography is thus useful in the management of newborns with a sacrococcygeal teratoma. It is essential not only to assess pelvic extension of tumour in relation to sacral promontory and pelvic brim, but also to look for intraspinal extension [6]. Our patients both had Altmann grade 1 sacrococcygeal teratomas with no other congenital abnormality. Both the patients were examined thoroughly before the procedure to delineate the extent of tumour and to rule out any spinal or nerve invasion using sonography.

Caudal anaesthesia in neonates is generally accepted as safe, even when administered by landmark technique. In contrast, the sacral multifidus plane block is a fascial plane block and may not be feasible without ultrasound guidance. Unlike caudal anaesthesia, it places the drug away from central neuraxis and in skilled hands does not carry the same risk of accidental dural puncture in neonates. Thus, the sacral multifidus plane block may be a viable alternative to caudal anaesthesia in neonates for peri‐operative analgesia. However, no data exist comparing caudal and sacral multifidus plane blocks in paediatric populations. Data regarding optimal doses of local anaesthetic, the craniocaudal spread of drug, the extent of bilateral spread from a midline injection, analgesic efficacy and safety are still not available, with a demonstrable lack of large prospective cadaveric, clinical and radiological studies. However, despite the lack of such data, this report nevertheless serves to demonstrate feasibility in applying the sacral multifidus plane block for postoperative analgesia in neonates undergoing surgical resection of sacrococcygeal teratomas.