Erector spinae plane block: anatomical landmark versus ultrasound-guided technique, a randomized controlled trial

Background As a practical interfascial plane regional analgesic technique, ultrasound-guided erector spinae plane block (ESPB) has been identified. Recently, landmark-guided ESPB has been described. We aimed to verify if the landmark-guided method was as effective as the ultrasound-guided method. Patients and methods In a parallel group equivalency trial, female patients aged 18 years or older of grades I and II American Society of Anesthesiology physical status, listed for breast surgery, were involved. The randomization order employed permuted blocks, with participants assigned equally to the ultrasound-guided (group U) or landmark-guided (group L) methods. Participants and assessors were blinded to group allocation. The primary endpoint was a block success rate as the equivalency outcome. Secondary endpoints included the extent of dermatomal spread, visual analog scale scores, total doses of perioperative opioid usage, the duration to the first demand dose of intravenous patient-controlled analgesia, and the occurrence of any adverse effects. Results One hundred twenty-four patients were randomized and analyzed in each group. The proportion of successful blocks (extended from T1 to T6 dermatomes) was 84.7% in the ultrasound-guided technique group and 83.1% in the anatomical landmark-guided technique group, with an absolute difference [95% confidence interval of −0.016 (−0.10 to 0.07)]; given that the equivalence margins were ±10%, we showed the equivalence of both techniques. There was no statistically significant difference in the mean dermatomal spread and the total perioperative consumption. The time to the first demand dose of morphine intravenous patient-controlled analgesia was statistically significantly longer in group U than in group L. The participants’ visual analog scale pain scores during rest after surgery showed a statistically significant difference, observed at 1, 3, 6, and 24 h. No block-related adverse effects were observed. Conclusions Landmark-guided ESPB provides an equivalent dermatomal blockade success rate to ultrasound-guided ESPB.