Background The mechanisms contributing to postoperative hyperalgesia (PH) in children are multifactorial. Recent evidence suggests a potential pathogenetic role for inflammation.

Objective To examine the relationship between serum concentrations of inflammatory mediators, cortisol (hydrocortisone) and PA after oncology surgicy.

Methods Prospective observational study involving children with PH after oncology surgery and normal controls. All patients after operation received adequate analgesic therapy (continuous infusion opioid analgesics). Blood samples were taken at birth from peripheral venous blood, at 8 h, 24 and 42 h for cytokines, cortisol and CRP after surgical procedure. The area of hyperalgesia for punctuate mechanical stimuli around the incision was measured 48 h after the operation with a hand-held von Frey filament. For statistical analysis 2 tests were used.

Results 26 children (12,2 +/- 2,4 years) with PA and 20 controls (12,8 +/- 3,1 years) were enrolled. 14/26 (53,8%) children with PH required mechanical ventilation. Children with PA had more than threefold higher serum levels of interleukin 8 (IL8) than the controls (p < 0.05). At 8 h, 24 h and 42 h, serum IL6 and CRP were 2.43- fold higher in neonates than the controls group (p < 0.003). All patients with PH had significantly (p < 0.001) higher plasma cortisol levels over control group (mean +/- SD, 464.42 +/- 56.40 vs. 202.21 +/- 37.30 micromol/l on 8 h; 752.02 +/- 96.4 vs. 308.12 +/- 100.1 micromol/l on 24 h; 600.04 +/- 62.3 vs. 302.8 +/- 51.2 micromol/l in 42 h).

Conclusion This study demonstrated that postoperative hyperalgesia syndrome is associated with raised blood levels of proinflammatory mediators and cortisol, suggesting that inflammation contributes to the PA.