The Role of Cytokines in Acute and Chronic Postsurgical Pain in Pediatric Patients after Major Musculoskeletal Surgeries.

STUDY OBJECTIVE: To determine if baseline cytokines and their changes over postoperative days 0-2 (POD0-2) predict acute and chronic postsurgical pain (CPSP) after major surgery.

DESIGN: Prospective, observational, longitudinal nested study.

SETTING: University-affiliated quaternary children's hospital.

PATIENTS: Subjects (≥8 years old) with idiopathic scoliosis undergoing spine fusion or pectus excavatum undergoing Nuss procedure.

MEASUREMENTS: Demographics, surgical, psychosocial measures, pain scores, and opioid use over POD0-2 were collected. Cytokine concentrations were analyzed in serial blood samples collected before and after (up to two weeks) surgery, using Luminex bead arrays. After data preparation, relationships between pre- and post-surgical cytokine concentrations with acute (% time in moderate-severe pain over POD0-2) and chronic (pain score>3/10 beyond 3 months post-surgery) pain were analyzed. After adjusting for covariates, univariate/multivariate regression analyses were conducted to associate baseline cytokine concentrations with postoperative pain, and mixed effects models were used to associate longitudinal cytokine concentrations with pain outcomes.

MAIN RESULTS: Analyses included 3,164 measures of 16 cytokines from 112 subjects (median age 15.3, IQR 13.5-17.0, 54.5% female, 59.8% pectus). Acute postsurgical pain was associated with higher baseline concentrations of GM-CSF (β=0.95, SE 0.31; p =.003), IL-1β (β=0.84, SE 0.36; p =.02), IL-2 (β=0.78, SE 0.34; p =.03), and IL-12 p70 (β=0.88, SE 0.40; p =.03) and longitudinal postoperative elevations in GM-CSF (β=1.38, SE 0.57; p =.03), IFNγ (β=1.36, SE 0.6; p =.03), IL-1β (β=1.25, SE 0.59; p =.03), IL-7 (β=1.65, SE 0.7, p =.02), and IL-12 p70 (β=1.17, SE 0.58; p =.04). In contrast, CPSP was associated with lower baseline concentration of IL-8 (β= -0.39, SE 0.17; p =.02), and the risk of developing CPSP was elevated in patients with lower longitudinal postoperative concentrations of IL-6 (β= -0.57, SE 0.26; p =.03), IL-8 (β= - 0.68, SE 0.24; p =.006), and IL-13 (β= -0.48, SE 0.22; p =.03). Furthermore, higher odds for CPSP were found for females ( vs. males) for IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, and TNFα, and for pectus ( vs. spine) surgery for IL-8 and IL-10.

CONCLUSION: We identified pro-inflammatory cytokines associated with increased acute postoperative pain and anti-inflammatory cytokines associated with lower CPSP risk, with potential to serve as predictive and prognostic biomarkers.