Nociception level index-directed superficial parasternal intercostal plane block vs erector spinae plane block in open-heart surgery: a propensity matched non-inferiority clinical trial

This single-center study explored the efficacy of superficial parasternal intercostal plane block (SPIPB) versus erector spinae plane block (ESPB) in opioid-sparing within Nociception Level (NOL) index-directed anesthesia for elective open-heart surgery. After targeted propensity matching, 19 adult patients given general anesthesia with preincisional SPIPB were compared to 33 with preincisional ESPB. We hypothesized that SPIPB is non-inferior to ESPB in reducing total intraoperative fentanyl consumption, with a non-inferiority margin (δ) set at 0.1 mg. Intraoperative fentanyl dosing targeted a NOL index ≤ 25. Postoperatively, paracetamol 1 g 6-hourly and morphine for numeric rating scale (NRS) ≥ 4 were administered. This study could not demonstrate that SPIPB was inferior to ESPB for total intraoperative fentanyl consumption, as the confidence interval for the median difference of 0.1 mg (95% CI 0.05-0.15) crossed the predefined δ, with the lower bound falling below and the upper bound exceeding δ, p = 0.558. SPIPB led to higher postoperative morphine use at 24 and 48 h: 0 (0-40.6) vs. 59.5 (28.5-96.1) µg kg^-1, p < 0.001 and 22.2 (0-42.6) vs. 63.5 (28.5-96.1) µg kg^-1, p = 0.001. Four times fewer SPIPB patients remained morphine-free at 48 h, p < 0.001, and their time to first morphine dose was three times shorter compared to ESPB patients, p = 0.001. SPIPB led to higher time-weighted average NRS scores at rest, 1 (0-1) vs. 1 (1-2), p = 0.004, and with movement, 2 (1-2) vs. 3 (2-3), p = 0.002, calculated over the 48-h period post-extubation. The SPIPB group had a significantly higher average NOL index, p = 0.003, and greater NOL index variability, p = 0.027. This study could not demonstrate that SPIPB was inferior to ESPB for intraoperative fentanyl consumption. Significant differences were observed in secondary outcomes, with SPIPB leading to higher postoperative morphine use, higher pain scores, and reduced nociception control.