Ultrasound-Guided Erector Spinae Plane Block for Breakthrough Cancer Pain in the Emergency Department: A Case Series

Background

Chronic pain is common among patients living with cancer. A recent meta-analysis of 444 studies revealed an overall pain prevalence of 44.5% and a 30.6% prevalence of moderate to severe pain among cancer patients. ¹ Opioids remain the primary modality of treating moderate to severe pain for patients with cancer. ² However, in response to the opioid epidemic, the number of opioid prescriptions for patients with cancer has declined in recent years, despite the difficulties of managing cancer-related pain.^3,4

When cancer patients experience breakthrough pain (BTP), they often present to the emergency department (ED). According to the CONCERN trial, the most commonly administered analgesic for these patients are short-acting opioids. ⁵ However, patients who received an opioid had a 1.56 increased odds of hospital readmission for BTP within 30 days of their initial ED visit. A separate 2020 study found that 66% of cancer patients admitted for BTP required an admission of over 72 hours and incurred a median cost of $48,156 per admission. ⁶

Cancer-related pain is challenging to treat due to its multifactorial physiology. ⁷ Somatic pain arises from malignant invasion of surrounding tissues. Visceral pain is caused by tumor-related stretching of visceral walls and capsules and disruption of surrounding ligaments and vasculature. Neuropathic pain comes from invasion of neural structures. ⁸ Treatment factors can further complicate cancer pain. Incisional pain, fibrosis, and muscle spasm from surgery contributes to somatic pain. Neurotoxic chemotherapies and radiation-induced fibrosis can cause neuropathic pain. ⁹

As emergency physicians seek alternative analgesics to opioids, there has been growing literature describing the use of regional anesthesia in the ED. The erector spinae plane block (ESPB) is a relatively novel procedure first reported in 2016 by Forero et al. for managing pain from rib fractures and metastases. ¹⁰ Recently, emergency physicians have adopted this procedure for truncal injuries and pain, including rib and spine fractures,^11,12 acute pancreatitis, ¹³ appendicitis, ¹⁴ and renal colic, ¹⁵ among other causes.

The ESPB has an excellent safety profile with rare complications. Risks include incomplete block, infection, local anesthetic systemic toxicity, pneumothorax, and spinal epidural hematoma. Yet there have been no reported confirmed cases of pneumothorax or epidural hematoma from this block. An absolute contraindication is overlying infection at the site.

Mechanistically, the ESPB is ideal for treating cancer-related pain. A single injection of anesthetic into the paraspinal fascia diffuses to coat the dorsal rami, ventral rami, and sympathetic chain. ¹⁶ The injectate also covers at least three spinal levels caudally and cranially, as demonstrated via MRI. ¹⁷ Thus, patients receive an extensive multi-level block against somatic pain carried by the ventral and dorsal rami, visceral pain carried by the sympathetic chain, and neuropathic pain. ¹⁸

This case series describes three patients with abdominal malignancy who presented to the ED with abdominal pain. The patients received an ESPB, resulting in significant and sustained reduction in pain. Pre- and post-procedure visual analog scale scores were obtained. The UC San Diego IRB granted a waiver of consent for this project, as it was deemed QA/QI. All patients consent to quality improvement/quality assurance and retrospective data review as part of our general registration and consent process.

Case 1

A 52-year-old woman with a history of metastatic rectal cancer presented with 7/10 lower abdominal pain for one week. Her outpatient pain regimen was with oxycodone 5–10 mg every four hours as needed. Her initial vitals were blood pressure 181/114, pulse 130, temperature 98.6°F, respiratory rate 18, and oxygen saturation of 100% on room air. On exam, her abdomen was soft with diffuse lower tenderness. A CT abdomen/pelvis with IV contrast revealed stable rectal/perirectal and hepatic metastases. Initially, she received a single dose of intravenous hydromorphone 1 mg. Two hours later, her pain returned at 7/10, and she was offered a bilateral ESPB at L1 with 20 mL of 0.25% bupivacaine per side.

Thirty minutes postprocedurally, her pain score was 0/10. She remained opioid-free until 17 hours post-procedure, at which point she was restarted on her home oxycodone regimen. She was discharged that evening and, a week later, reported complete resolution of pain at a telehealth visit.

Case 2

A 44-year-old man with a history of metastatic rectal cancer presented with two days of 8/10 diffuse abdominal pain. His outpatient pain regimen was oxycodone 5 mg every six hours as needed. His initial vitals were blood pressure 118/82, pulse 109, temperature 99°F, respiratory rate 16, and oxygen saturation of 98% on room air. On exam, his abdomen was soft with diffuse lower tenderness. A CT abdomen/pelvis with IV contrast revealed progression of rectal, hepatic, and bladder masses. Initially, he received two doses of intravenous hydromorphone 1 mg. Four hours later, his pain returned at an 8/10, and he was offered bilateral ESPB at L1 with 20 mL of 0.25% bupivacaine with dexamethasone 5 mg per side.

Thirty minutes postprocedurally, his pain score was 2/10. He ambulated without difficulty and requested discharge two hours later. On 24-hour routine telephone follow-up, he reported continued 80% improvement of pain and function and full satisfaction with his ED care.

Case 3

A 63-year-old woman with a history of metastatic pancreatic adenocarcinoma presented with 10/10 diffuse abdominal pain. Her outpatient pain regimen was oxycodone-acetaminophen 5–325 mg every four hours as needed. Her initial vitals were blood pressure 193/124, pulse 101, temperature 96.7°F, respiratory rate 18, and oxygen saturation of 97% on room air. On exam, her abdomen was soft with diffuse, primarily epigastric, tenderness. A CT abdomen/pelvis with IV contrast revealed an improved pancreatic pseudocyst versus seroma adjacent to her subtotal pancreatectomy site and duodenal inflammation. Prior to being offered an ESPB, she received two doses of intravenous hydromorphone, 1 mg. Three hours later, her pain returned at 6/10, and she was offered bilateral ESPB at T6. She received 20 mL of 0.25% bupivacaine with dexamethasone 5 mg per side.

Fifteen minutes postprocedurally, her pain score was 2/10. She was discharged from the hospital the next day without the need for additional opioids.

Discussion

In all three cases, ESPB provided significant, sustained analgesia, facilitating discharge without the need for rescue opioids (Table 1). Prior to the procedure, the patient in case 3 received two doses of IV hydromorphone an hour after each other and required supplemental oxygen secondary to bradypnea, highlighting the danger of stacking rescue opioids and the need for alternatives or adjuncts.

There was variability between cases, primarily in target level selection and composition of injectate. Level selection was primarily based upon dermatomal association. The first two patients discussed had a history of rectal cancer with lower abdominal tenderness and thus were treated at L1. The third patient had a history of pancreatic cancer with epigastric tenderness and was treated at T6.

While the use of dexamethasone was not standardized, all three patients had a similarly robust response. Case 1 received bupivacaine alone and had a profound 17-hour response that exceeded its half-life of 3.5 hours. ¹⁹ Dexamethasone was added to case 2 and 3′s injection. Dexamethasone has been shown to increase the duration of analgesia when added to nerve blocks. Its half-life is 36–54 hours. ²⁰ One meta-analysis of 27 randomized controlled trials showed a mean duration difference of 6.7 hours with adjunctive dexamethasone compared to placebo. ²⁰ Proposed mechanisms include inhibition of inflammatory mediator release, reduction in ectopic neuron discharge, and inhibition of nociceptive fiber discharge.

Until better-powered studies are performed, these patients should still be admitted or observed as their pain crises may return as the block wears off. Patients should only be considered for discharge if there is confirmed close follow-up with their outpatient palliative or oncology team and clear discharge instructions and return precautions. Otherwise, patients should still be admitted or observed in the department.

An emergency medicine resident performed all three ESPBs under the supervision of an attending physician without formal ultrasound or pain management training. The ESPB does not involve specialized equipment and can be accomplished using standard supplies found in most emergency departments. After positioning and skin prep, the procedure should take 10–15 minutes to complete bilaterally, perhaps with additional time needed for challenges associated with anatomical variance. This procedure is within the scope of procedural abilities for emergency physicians who routinely perform ultrasound-guided procedures.

Limitations

A major limitation of this study is that in each case, the patients were bridged to ESPB with an additional IV opioid, confounding their response to ESPB alone. However, the sustained effect lasted beyond the half-life of the opioids, supporting our conclusion that the ESPB was the primary reason for the robust response. A control group receiving standard of care would be helpful in elucidating the efficacy of ESPB. We hope to address these limitations in a future prospective, randomized clinical trial.

Conclusion

In conclusion, our case series describes three patients with cancer-related abdominal pain who were successfully treated with the ESPB block. Acute exacerbations of cancer pain are difficult to manage, and opioids are associated with significant complications. We hope that this article demonstrates a starting point for future research into this promising and effective analgesic method.