Does Post-Surgery Placement of Rectus Sheath Block Analgesia Alter the Oxidative Stress Biomarker 8-OHdG Concentrations: A Randomised Trial of Patients with Cancer and Benign Disease.

BACKGROUND The aim of the study was to evaluate whether the post-surgery placement of the rectus sheath block (RSB) analgesia could alter the oxidative stress response. The main hypothesis of our study was to find some correlation between patients' pain experience, numeric rating scale (NRS) and the concentration of oxidative stress marker, 8-OHdG (8-hydroxy-2'-deoxyguanosine) in patients with benign disease and cancer. MATERIALS AND METHODS Initially, 46 patients were randomized to the placebo group (n=11) and to one of the three active groups; single-dose (n=12), repeated-dose (n=12) and continuous infusion (n=11) RSB analgesia group. The plasma concentrations of the hs-C-reactive protein (CRP) and 8-OHdG were measured at three time points: just before, immediately after and 24 h after operation. The primary end-point was to compare plasma concentrations of the hs-CRP and 8-OHdG in the placebo group and in the three different RSB analgesia groups in patients with benign disease and cancer. RESULTS The placebo group and three active groups were similar in terms of demographic variables and the perioperative data. The patients in the continuous infusion group had a trend for lower median 8-OHdG values post-operatively than the three other study groups (p=0.147; in all patients with benign disease and cancer). The patients in the cancer group showed a trend for higher median 8-OHdG values in the repeated-dose group than the patients in the benign group (p=0.241). There was a significant inverse correlation between the individual values of the plasma hs-CRP and 8-OHdG in patients with benign disease and cancer (r=-0.40, p=0.02). However, there was no significant correlation between the individual values of the NRS score and 8-OHdG post-surgery in patients with benign disease and cancer. CONCLUSION The results suggest that the placement of RSB analgesia does not significantly alter the oxidative stress marker 8-OHdG concentrations in patients with benign disease or cancer patients. A new finding with possible clinical relevance is a significant inverse correlation between the individual plasma values of the hs-CRP and 8-OHdG in patients with benign disease and cancer.