The Use of Lumbar Erector Spinae Plane Block for Hip Arthroplasty at the L4 Interspace

Over 300,000 hip arthroplasties are performed each year in the United States.1 This number has been steadily increasing over the last two decades, likely due to increased life expectancy and, more significantly, the obesity epidemic. Traditionally, this procedure has been performed under general anesthesia. However, neuraxial and regional anesthesia have become more commonly utilized to aid in postoperative analgesia. Postoperative pain control has a significant impact on earlier ambulation, initiation of physical therapy, better functional recovery, and overall patient satisfaction.2 Moreover; optimal pain management can reduce the duration of hospitalization and the risk of adverse events, such as deep vein thrombus. The use of regional anesthesia reduces the postoperative opioid requirement, thereby decreasing the degree to which patients suffer the side effects of opioids, namely sedation and constipation, and less frequently nausea, vomiting, respiratory depression, pruritus, and retention. In the past, femoral nerve block, fascia iliaca compartment block, lumbar plexus block and the quadratus lumborum block have been shown efficacious for pain relief for hip arthroplasty. However there are several risk factors such as quadricep weakness and difficulty of the block that causes a limitation in the used of this blocks. Recently, the erector spinae plane block has been introduced as an alternative to the blocks above. This block was first described in the literature in 2016 when it was used to treat chronic neuropathic thoracic pain. Since then, there have been studies demonstrating its efficacy with a thoracic approach for analgesia in breast surgery and rib fractures.9 Only two case reports to date have demonstrated a lumbar approach to achieve analgesia for hip arthroplasty.10,11 The purpose of the study is to determine whether or not a lumbar erector spinae plane block is effective at improving postoperative pain in patients receiving hip arthroplasty.

Hypothesis:

The erector spinae plane block will decrease opioid requirements in patients undergoing hip arthroplasty as compared to patients that do not receive the block.

Primary Objective:

To compare the opioid consumption in the post-anesthesia care unit (PACU) and at 24 hours postoperative (in morphine equivalents) in patients receiving regional anesthesia with spinal vs. spinal alone.

Secondary Endpoints:

To evaluate the pain scores at discharge from PACU, at 2 hours post PACU discharge, at 24 hours and at 48 hours postoperative; to evaluate the sensory distribution of the block (T10-L5); to evaluate whether or not patients that receive the block have evidence of quadricep muscle weakness

Design and methods This is a randomized, prospective study in patients receiving hip arthroplasty. Patients will be assigned to receive a lumbar erector spinae block versus no block. There will be no change in the primary anesthetic technique (spinal anesthesia with sedation) since these patients routinely get spinal anesthesia for hip arthroplasty. Consent for the study will be obtained in the preoperative area upon arrival for surgery. Patients will then be randomized into one of the two groups above. One group will receive a lumbar erector spinae block at L4 with 30ml of 0.375% ropivacaine with 50 mcg of dexmedetomidine before the procedure using ultrasound guidance. The second group will receive no peripheral nerve block to serve as the control. Patients to receive a nerve block will receive mild sedation (1-2mg midazolam ± ≤100mcg fentanyl). All patients receiving nerve blocks will have a printed image of the block thus to confirm proper spread of local anesthetic both cranially and caudally.

Postoperatively, the PACU nurse will be asked to document pain scores according to the Visual Analog Scale (VAS) and total dose of opioids given. The distribution of the sensory block and motor weakness will be documented in the anesthesiologist's PACU discharge note. For patients that receive the block, the Physical therapist note will be assessed for any report of quadriceps muscle weakness (i.e., evidence of buckling while walking).

For postoperative data collection, opioid consumption totals and the pain scores at 2 hours post admission, at 24 hours and 48 hours post-procedure will be collected from the electronic medical record (EMR) as documented by nurses on the admitting floor. Additionally, the Acute Pain service, who rounds on all patients that receive nerve blocks, will make a note of the pain scores of the patient and any residual muscle weakness or decreased sensation at 24- and 48-hours post-procedure. All data will then be extracted from the EMR by the research assistant.

Eligibility Criteria:
Inclusion Criteria:

* Patients undergoing primary hip arthroplasty
* American Society of Anesthesiologists (ASA) Category 1, 2, and 3
* Patients age ≥18 years

Exclusion Criteria:

* Patient refusal
* Inability to understand and sign consent
* Infection at the injection site
* Known allergy or hypersensitivity to ropivacaine or other amide local anesthetics
* Contraindication or patient refusal to get spinal anesthesia
* Thrombocytopenia (platelets \< 100,000)
* Coagulopathy (INR \> 1.4)
* Use of anticoagulant drugs that have not been discontinued in an appropriate amount of time before the surgery
* ASA Category 4 and 5