Evaluation of Sensory Mapping of Erector Spinae Plane Block

Background: Erector spinae plane (ESP) block is an effective regional analgesic technique for thoracic and abdominal pain. The volume of local anesthetic (LA) needed to produce sensory block in the spinal segment is unknown.

Objectives: The aim of the present study was to examine the extent of dermatomal spread following ultrasound-guided administration of ESP block, with a fixed-volume dose of a LA at the midthoracic area for analgesia in acute thoracic pain patients. Secondary objectives were postprocedure analgesia and patient satisfaction.

Study design: This research used a prospective unicentric exploratory cohort design.

Setting: The study was conducted at an academic university hospital.

Methods: A total of 18 patients with acute severe chest pain including rib fractures, thoracic postoperative rescue analgesia, zoster herpetic neuritis, and myofascial pain syndrome received ESP block under ultrasound guidance at the T5-T7 levels. Twenty mL of 0.5% plain bupivacaine was injected. Evaluation of the sensory block was carried out 60 minutes following the completion of the ESP block via a change in sensation to pinprick and cold methods. The Visual Analog Scale (VAS) for pain was recorded one hour after the procedure. Patient satisfaction was reported using a 4-point Likert scale. This study was registered with the clinicaltrials.gov database (identifier: NCT03831581).

Results: Sixteen patients had a successful ESP block; 2 patients were excluded for a failed block. The mean dermatomal spread was 9 (range, 8-11). VAS scores improved by at least 50% from baseline (P < .05), one hour after the ESP block. The degree of satisfaction reported by all patients on the Likert scale was 4 points. No major complications were observed.

Limitations: This study was limited by its sample size.

Conclusions: An ultrasound-guided ESP block with a single injection at the midthoracic level with 20 mL of 0.5% plain bupivacaine provides a mean dermatomal spread of 9 dermatomes (range, 8-11) with a high rate of analgesic efficacy and low incidence of adverse effects.

Key words: Acute pain, dermatomal spread, erector spine plane nerve block, thoracic pain, thoracic postoperative analgesia.