a b s t r a c t

Sciatic radicular back pain is a painful condition resulting in approximately 2% of emergency department (ED) visits a year. Typically, the ED treatment has been limited to various analgesic regimens with limited success sometimes resulting in hospital admissions for pain control. regional anesthesia has become increasing popular for lower-limb analgesia, but has not universally permeated the ED setting. The transgluteal sciatic nerve block (TGSNB) is a procedure that can provide effective analgesia for Lower extremity pain. Herein, we present the first technical description and Clinical response to ultrasound-guided TGSNB performed by emergency physicians for Acute pain control of sciatic back pain through a series of cases.

(C) 2020

Introduction

Sciatica is radicular pain radiating down the buttocks along the course of the sciatic nerve. It is responsible for up to 2.4% of visits in the emergency department (ED) in the United States annually [1]. Pain outcomes for these patients are poor; almost 70% continue to have pain one week after their ED visit and 46% report persistent anal- gesic use three months after [2].

Typically, the ED treatment of sciatica pain is limited to various anal- gesic regimens. Nonsteroidal anti-inflammatory drugs pro- vide superior pain relief when compared to placebo [3]. Opioids are commonly used in the treatment for sciatica, however the long-term potential for misuse and abuse drastically decreases their utility outside of the ED [4]. In addition, recent data demonstrate that a single dose of opioids in the ED is not superior to alternatives [5]. Further, muscle re- laxants also have no benefit for acute low back pain [6,7]. With such lim- case presentations”>ited options for managing acute pain, additional modalities are needed.

* Corresponding author at: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA, United States of America.

E-mail addresses: [email protected] (A.J. Goldsmith), [email protected] (A. Liteplo), [email protected] (B.D. Hayes), [email protected]

(N. Duggan), [email protected] (C. Huang), [email protected] (H. Shokoohi).

Regional anesthesia is increasingly popular for lower-limb analgesia for patients presenting with acute pain [8,9]. The transgluteal sciatic nerve block (TGSNB) is a well-established procedure that is widely used by anesthesiologists both post-operatively and for chronic pain [10-13]. Although well-described in the anesthesia literature, TGSNB has been slow in finding its path to the ED, and we found no report on its application in the ED. Analgesia for sciatica has multiple applications within the ED, particularly for acute-on-chronic sciatic radiculopathy.

ED physicians routinely perform nerve blocks as part of usual clinical care. These are now more commonplace as the use of ultrasound guid- ance has permeated residency training. Ultrasound-guidance permits the visualization of the nerve tissue, needle and spread of local anes- thetic thereby improving the efficacy and safety profile of regional anes- thesia [14,15]. Herein, we present the first technical description and clinical response to ultrasound-guided TGSNB performed by emergency physicians for acute pain control of sciatic back pain.

Case presentations

Case 1

A 27-year-old female with a known L5-S1 disc extrusion presented with left-sided radicular back pain down the posterior left leg and ankle. Her ability to ambulate was significantly decreased. On exam, the patient had paraspinal spasm and tenderness but she demonstrated

https://doi.org/10.1016/j.ajem.2020.06.001

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appropriate strength and sensation in her lower extremities. Her spinal movements ware restricted due to pain, and her straight leg raise test was positive at about 30-40?. Despite taking oxycodone 5 mg every 6-8 h, cyclobenzaprine 5 mg nightly, and naproxen 500 mg twice a day, she presented with 10/10 pain and was unable to perform her ac- tivities of daily living. In the ED, the patient received acetaminophen 975 mg and ibuprofen 600 mg prior to consenting to a TGSNB. Subse- quently, a TGSNB was performed with 15 mL of 0.5% bupivacaine and dexamethasone 10 mg perineurally. One hour after the procedure the patient reported her pain at 1/10.

Case 2

A 45-year-old female with a known L5-S1 disc extrusion presented with acute-on-chronic right sided radicular back pain down the poste- rior right leg and ankle. A Neurological examination showed no abnor- mality in her bilateral lower extremities except a positive left straight leg raise test. She had limited strength in her right leg secondary to pain. She had refused a surgical intervention that had been offered and was treated conservatively with bed rest, NSAIDs, and analgesics nearly for three weeks. Despite taking oxycodone 10 mg the night prior and ibuprofen 600 mg at home she was unable to ambulate due to 10/10 pain. A TGSNB was performed with 15 mL of 0.5% bupivacaine and dexa- methasone 10 mg perineurally. Approximately an hour later the patient

reported significant pain relief with a reported pain at 1/10.

Case 3

A 40-year-old male with a known L4-L5 disc extrusion presented with acute-on-chronic right sided radicular back pain down the poste- rior right leg. Previously, Conservative therapy including bed rest, phys- ical therapy, NSAIDs, and analgesics had been advised, as he had no neurological deficit. On physical examination, he had a positive straight leg raise test but was otherwise neurovascularly intact in both his lower extremities. Despite taking ibuprofen 600 mg and cyclobenzaprine 5 mg 6 h prior to arrival the patient described his pain as 10/10. The patient received oxycodone 5 mg, naproxen 500 mg, and acetaminophen 975 mg in the ED, but the pain was still rated 10/10 one hour later. A TGSNB performed with 15 mL of 0.5% bupivacaine and dexamethasone 10 mg perineurally. One hour after the procedure the patient reported substantial improvement with his pain as 3/10.

The TGSNB procedures were directly performed or supervised by an emergency ultrasound trained fellow with extensive training and expe- rience in regional anesthesia. Within 20-30 min of performing an TGSNB, all three patients were able to ambulate with less pain. Prior to this TGSNB strategy, patients with this type of pain presentation would have required intravenous (IV) analgesia and possibly an over- night admission. None of the patients had any motor deficits or any

other complications and all were able to ambulate and walk out of the ED without additional support. A follow-up phone call 24 h after the TGSNB confirmed that patients had a minimum of 16 h of pain relief. One patient had up to 24 h. When the pain returned, it was decreased compared to when in the ED. Of note, none of these patients had ever had this procedure before. On discharge, all patients mentioned that they would have this procedure again if offered.

Description of technique

Pre-assessment

Inspect the lateral proximal thigh for evidence of infection or excess soft tissue. If neither are present, a thorough neurological evaluation of the affected leg should be performed. Patients with evidence of infec- tion, excessive soft tissue, or signs of motor dysfunction are poor candi- dates for a TGSNB.

Positioning

Expose the proximal lateral aspect of the patient’s affected leg and place the patient in the lateral decubitus position with the affected side up and the knee flexed at a 90? angle. The ultrasound machine should be placed on the side of the bed that the patient is facing and the operator should be standing on the other side. The bed should be el- evated to a level where the needle, probe, and ultrasound screen can all be viewed in a direct line-of-site with minimal movement.

Bupivacaine and dexamethasone

The recommended solution is a mixture of 0.5% bupivacaine (to a maximum of 2 mg/kg, or 0.4 mL/kg) and dexamethasone 10 mg perineurally. Perineural dexamethasone increases the duration of sen- sory blocks by upwards of 8 h with no reported risk of adverse events [16]. Although not tested in EM, a Cochrane review of 35 studies dem- onstrates moderate evidence for its use to prolong the duration of sen- sory blocks [17]. Our main goal by using this combination was to provide pain relief for the longest duration possible for the patient.

Identifying block location and injection

The sciatic nerve is formed from the L4-S3 segments of the sacral plexus. After leaving the lower vertebrae the nerves converge to form the longest and widest single nerve in the human body [18]. Specifically, the nerve exits the pelvis through the greater sciatic foramen adjacent to the piriformis muscle and descends between the greater trochanter and ischial tuberosity (Fig. 1). The nerve then progresses posterior to the hamstring down to the foot providing sensation to the posterior

Fig. 1. MRI of sacral spine in both coronal (a) and sagittal (b) depicting the course of the lumbosacral plexus and the sciatic nerve. The lumbosacral plexus can be seen exiting the lumbar and sacral spine forming the sciatic nerve as it courses adjacent to the pyriformis and inferior to the Gluteus maximus.

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thigh, anterior, lateral and posterior leg in addition to motor function to those same compartments.

The TGSNB targets the sciatic nerve at the level of the great trochan- ter. The sciatic nerve is identified in cross section at the level of the is- chial tuberosity (medially), greater trochanter (laterally), gluteus maximus (superior) and quadratus femoris (inferior) (Fig. 2).

With the patient in the lateral decubitus position, palpate for the greater trochanter laterally and the posterior superior iliac spine medi- ally. A line between the two landmarks will indicate the path of the nee- dle. A curviLinear probe (1-5 MHz) should be placed along this line. The greater trochanter should be located laterally and the ischial tuberosity should be located medially. The sciatic nerve will appear as a flattened, round or triangular hyperechoic structure lying within the fascial plane between the gluteus maximus and quadratus muscles. It will usually be located about 4-6 cm below the skin (Fig. 2).

With the transducer fixed over the targeted nerve, identify a needle insertion site approximately 1-2 cm away from the probe. The site can be either cephalad or caudad to the probe as the sciatic nerve can be approached from either direction.

After sterile prep, place a lidocaine skin wheal at the insertion site using a 27 g needle. Then insert a block needle (i.e. Sonoplex 22G 90 mm) and advance at 70-90? toward the sciatic nerve. After the 1-2 cm of insertion, stop further needle advancement and make subtle probe adjustments until the needle is visualized. Continue advancing with in-plane ultrasound guidance to position the needle tip approxi- mately 1-2 cm away from the nerve.

Once the needle tip is visualized adjacent to the sciatic nerve, aspi- rate prior to injecting small aliquots of solution. Anechoic fluid should be seen separating the fascial plane away from the sciatic nerve. The

needle should be readjusted to circumferentially provide anesthetic around the entire sciatic nerve. The operator should aspirate prior to injecting any solution after the needle is repositioned. If resistance is met, the needle should be slightly withdrawn and reconfirmed on ultra- sound prior to injection. A total of approximately 10-15 mL of bupivacaine and dexamethasone mixture is suggested. In our experi- ence, the total procedure time was less than 5 min.

Discussion

Sciatic pain can be a difficult condition to manage in the ED. Current ED pain management regimens are limited, especially with opioids being phased out. As an alternative to providing IV opioids and poten- tially admitting the patients for pain control, a TGSNB was performed and all three patients ambulated and were successfully discharged from the ED. TGSNB was performed in all three patients rather than a more distal sciatic anesthetic block given the proximity to the likely source of the patients pain (i.e. herniated disc). TGSNBs were well- tolerated and significantly improved patient comfort. All three patients experienced no motor dysfunction or had any adverse events.

The natural question is should emergency physicians be performing this? Much of the published regional anesthesia evidence comes from the anesthesia literature, where TGSNBs are used successfully for post- operative pain relief with extremely low adverse events [10-13]. Given the possible significant benefit of pain relief and satisfaction, and the potential cost-saving impact from avoiding admission, there is opportunity for EDs to employ this technique.

We believe that the TGSNB is a useful and successful regional anes- thesia technique for a selected group of patients with back pain and

Fig. 2. patient positioning and technique for performing TGSNB. A. Positioning patient in a lateral decubitus position with identification of anatomical landmarks and its corresponding ultrasound image (B) using a curvilinear probe. (C) The needle is inserted 1-2 cm away from the probe at approximately 75? degree angle toward the ischial tuberosity. (D) Anechoic fluid is then injected in small aliquots surrounding the sciatic nerve. GT = greater trochanter, GM = gluteus maximus, SN = sciatic nerve, IT = ischial tuberosity, triangles = needle, L = local anesthetic.

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radiculopathy. The impact on reducing opioid use and patient discom- fort in the ED may be substantial. It is a feasible and safe procedure that requires only a single injection. Although this small case series demonstrated its efficacy when performed correctly, all three blocks were performed and/or supervised by an EM ultrasound fellow trained physician. Currently, there is limited data describing the safety and effi- cacy of the TGSNB in the ED.

Further, clinicians should prioritize appropriate patient selection and be aware of the general risks associated with a nerve block, includ- ing LAST syndrome and Peripheral nerve injury [14]. IV lipid emulsion should be readily available in EDs performing TGSNB [19]. Patients with extensive tissue between the skin surface and sciatic nerve are suboptimal candidates for TGSNB given the potential of technical diffi- culty. Further variability in providing circumferential anesthetic to the nerve may reduce the length of pain relief. More data is needed to deter- mine its efficacy and safety in the ED.

Conclusion

Our initial experience suggests that the TGSNB is technically feasible and highly efficacious for the management of acute on chronic sciatic ra- dicular pain. In this case series, all three patients had no adverse out- comes and had excellent pain relief. Further studies are needed to confirm its effectiveness within the ED as well as emergency providers comfort performing it.

Author credit statement

Andrew J. Goldsmith, MD, MBA: Conceptualization, Writing Original Draft.

Andrew Liteplo, MD: Writing- Reviewing and Editing, Supervision. Bryan D. Hayes, PharmD: Writing- Reviewing and Editing.

Nicole Duggan, MD: Visualization, Writing- Reviewing and Editing. Calvin Huang, MD: Visualization, Writing- Reviewing and Editing. Hamid Shokoohi, MD MPH: Writing- Reviewing and Editing,

Supervision.

Presentations

None.

Financial support

None.

Declaration of competing interest

The authors report no conflict of interest.

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