Pain Outcomes and Perioperative Cytokine Responses After Intrathecal Morphine or Erector Spinae Plane Block for Caesarean Delivery: A Prospective Observational Cohort Study

Background/Objectives: To compare perioperative cytokine profiles, four-month chronic pain, acute analgesia, and recovery among women receiving intrathecal morphine (ITM) or erector spinae plane block (ESPB) after elective caesarean delivery. Methods: In this prospective observational cohort, 88 women received ITM (50 μg; n = 44) or bilateral ESPB (0.25% bupivacaine, 20 mL/side; n = 44) as part of routine care. Serum IL-6, TNF-α, and IL-10 were measured at baseline, 6 h, and 24 h. Results: Clinically relevant acute pain occurred in 13/44 (29.5%) ITM versus 25/44 (56.8%) ESPB participants (unadjusted risk difference, −27.3 percentage points; 95% CI −44.9 to −6.6). No rescue analgesia was required by 21/44 (47.7%) versus 4/44 (9.1%) (risk difference, 38.6 percentage points; 95% CI 20.2 to 54.0). Mean ObsQoR-11 scores were 95.05 ± 7.49 versus 91.52 ± 6.91 (mean difference, 3.53 points; 95% CI 0.48 to 6.58). Baseline IL-6 and IL-10 concentrations differed; an exploratory baseline-adjusted analysis showed an IL-10 group-by-time interaction after Holm correction. Chronic pain occurred in 3/44 (6.8%) versus 6/44 (13.6%) (risk difference, −6.8 percentage points; 95% CI −20.6 to 6.7). Conclusions: ITM receipt was associated with lower early pain burden and fewer rescue analgesic requirements, but treatment selection was non-randomised and associated with clinician identity. Cytokine findings are exploratory; chronic pain comparisons remain inconclusive.