Does Rectus Sheath Block Analgesia Alter Levels of the Oxidative Stress Biomarker Glutathione Peroxidase: A Randomised Trial of Patients with Cancer and Benign Disease

Aim: To evaluate whether the overall satisfaction, as measured by numeric rating scale (NRS), regarding rectus sheath block (RSB) analgesia is associated with the plasma glutathione peroxidase (GPX1) level. The second end-point of the study was to evaluate the differences in GPX1 levels in patients with and without RSB analgesia, with special emphasis on benign or malign disease status. Patients and Methods: Initially, 56 patients were randomized to the placebo group (n=12) and to one of three active RSB analgesia groups: single-dose (n=16), repeated-dose (n=12) and continuous infusion (n=16) groups. The plasma level of GPX1 was measured at three time points: just before, immediately after and 24 h after surgery. The overall satisfaction and an opinion on the success of the analgesic procedure were surveyed using an 11-point numeric rating scale 24 h postoperatively (NRS from 0, completely dissatisfied, to 10, fully satisfied). Results: The placebo group and the three active groups were similar in terms of their perioperative data. The plasma level of GPX1 decreased postoperatively in all four groups. No differences were detected in the GPX1 values between the placebo and the three active groups combined preoperatively and immediately after operation. However, the patients in the single-dose group had a significantly lower median GPX1 values 24 h after surgery compared to the three other groups separately (p=0.032). The median (interquartile range) plasma level of GPX1 differed significantly between patients with benign disease and those with cancer preoperatively (18.0, 12.5-22.0 versus 10.0, 6.3-18.8 pg/ml, p=0.006) and cancer diagnosis was correlated with lower individual plasma GPX1 values (r=–0.42, p=0.004). Conclusion: The placement of RSB analgesia does not significantly affect the level of oxidative stress biomarker GPX1 in patients with benign disease or cancer. A new finding with possible clinical relevance is that patients with cancer appeared to have a trend for lower plasma GPX1 values.

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