Surgery · Medical Literature
Comparison of ultrasound-guided serratus posterior superior intercostal plane block and thoracic paravertebral block for postoperative analgesia after breast surgery: a prospective randomized noninferiority trial.
Abstract
This noninferiority trial aimed to evaluate whether the serratus posterior superior intercostal plane block (SPSIPB) provides noninferior postoperative analgesia compared with the thoracic paravertebral block (TPVB) after unilateral mastectomy. This prospective, randomized, assessor-blinded, parallel-group noninferiority trial enrolled 60 female patients scheduled for elective unilateral mastectomy. Patients received either ultrasound-guided SPSIPB (n = 30) or TPVB (n = 30) with 30 mL of 0.25% bupivacaine before induction. The primary outcome was visual analogue scale (VAS) pain scores (0-100 mm) at rest and during coughing over 24 h. Noninferiority was assessed using the Hodges-Lehmann median difference with 95% confidence intervals (CIs) and a prespecified margin of 13 mm, corresponding to the validated minimal clinically important difference (MCID). Secondary outcomes included opioid consumption, area under the curve (AUC) for cumulative pain burden, and patient satisfaction. All 60 patients completed the study. At the first postoperative hour, TPVB provided lower VAS scores at rest (median 10.0 vs. 23.0 mm, 95% CI of difference: 0 to 19). For resting VAS, noninferiority was demonstrated at 0 h, 4 h, and 24 h (upper bounds: 11.5 mm, 12.5 mm, and 5.0 mm). The 24-h AUC for resting VAS was comparable between groups (426 mm/h vs. 426.5 mm/h, p = 0.652). SPSIPB produced significantly lower tramadol consumption in the 12-to-24-h interval (median 0 vs. 50 mg, p < 0.001). However, total opioid consumption over the 24 h was comparable (p = 0.070). No block-related complications occurred in either group. Noninferiority of SPSIPB to TPVB was demonstrated for resting pain scores at the majority of postoperative time points after unilateral mastectomy. TPVB provided a transient early-phase analgesic advantage at 1 h and 2 h, while SPSIPB was associated with late-phase opioid sparing. The comparable cumulative pain burden across 24 h suggests that SPSIPB may serve as a periparavertebral alternative to TPVB when sustained analgesia and opioid reduction are clinical priorities.
Clinical relevance
This prospective randomized noninferiority trial addresses a critical gap in regional anesthesia for breast surgery by evaluating whether the serratus posterior superior intercostal plane block (SPSIPB) — a technically simpler, potentially safer periparavertebral alternative — can match the analgesic efficacy of the established thoracic paravertebral block (TPVB). The study population consists of women undergoing elective unilateral mastectomy, a procedure associated with significant acute postoperative pain and high opioid utilization. As surgeons and anesthesiologists seek effective yet accessible regional techniques with favorable safety profiles, this evidence is immediately clinically actionable for perioperative pain management teams.
Key findings
1. Noninferiority of SPSIPB vs. TPVB for resting VAS pain scores was demonstrated at the majority of assessed time points (0 h, 4 h, and 24 h), with upper bounds of the 95% CI of the Hodges-Lehmann median difference at 11.5 mm, 12.5 mm, and 5.0 mm, respectively — all below the prespecified noninferiority margin of 13 mm (MCID). 2. TPVB provided a statistically and potentially clinically meaningful early analgesic advantage at postoperative hour 1 (median VAS: 10.0 mm vs. 23.0 mm; 95% CI of difference: 0 to 19 mm), exceeding the noninferiority margin, with a similar pattern observed at hour 2 — indicating noninferiority was NOT met at these early time points. 3. The 24-hour area under the curve (AUC) for cumulative resting pain burden was equivalent between groups (426.0 mm·h vs. 426.5 mm·h, p = 0.652), confirming comparable overall pain experience across the full postoperative day. 4. SPSIPB was associated with significantly lower tramadol consumption during the 12-to-24-hour interval (median 0 mg vs. 50 mg, p < 0.001), suggesting a late-phase opioid-sparing advantage. 5. Total 24-hour opioid consumption did not reach statistical significance between groups (p = 0.070), indicating overall opioid use was broadly comparable. 6. No block-related complications were recorded in either group (n = 30 per arm), supporting the safety profile of both techniques in this cohort.
Practice implications
For female patients undergoing elective unilateral mastectomy, SPSIPB may be considered a viable periparavertebral alternative to TPVB when the clinical priority is sustained 24-hour analgesia and late-phase opioid reduction, particularly in settings where TPVB expertise or safety conditions (e.g., coagulopathy risk, proximity to neuraxial structures) are limiting factors. Clinicians should note that TPVB retains a transient analgesic superiority in the first 1–2 postoperative hours, and therefore SPSIPB-based protocols may benefit from supplemental multimodal analgesia (e.g., IV acetaminophen, NSAIDs, or a short-acting opioid rescue) during the immediate recovery period to bridge this early gap. Both blocks were performed with 30 mL of 0.25% bupivacaine under ultrasound guidance before induction; replication of this dosing and timing protocol is important when translating these findings to clinical practice.