Effects of antiemetic doses of dexamethasone on plasma mediators of inflammation resolution and pain after surgery in women.

BACKGROUND

Dexamethasone is commonly given as an antiemetic during surgical procedures. It has immunosuppressive effects and can affect key enzymes involved in the synthesis of specialised lipid mediators of inflammation resolution (SPM) that direct inflammation resolution and have anti-nociceptive actions. This study examined the effect of dexamethasone on plasma SPM, and the relationship between SPM and perceived pain in women undergoing surgery.

METHODS

Plasma SPM were measured in samples obtained from two double-blind controlled interventions. The first, included 51 women mean age 53 ± 1.5 years, undergoing breast surgery allocated to either intravenous saline, or dexamethasone (4 mg or 8 mg) after induction of anaesthesia. The second study included 31 women of mean age 44 ± 0.5 years undergoing laparoscopic gynecological surgery that were allocated to either saline, or dexamethasone (4 mg). SPM (18-HEPE, 17-HDHA, RvE2, RvD1 17R-RvD1 and RvD2) were measured in plasma collected prior to induction of anaesthesia and at 24 h, and 6 weeks post-surgery. Pain was assessed using a verbal analogue scale at discharge from the post-anaesthesia recovery unit. The data from each study was combined to examine the effect of dexamethasone on plasma SPM. The relationship between pain score and SPM was examined using ordinal logistic regression.

RESULTS

The SPM 18-HEPE, 17-HDHA, RvE2, RvD1 17R-RvD1 and RvD2 were detectable in all plasma samples. There was no significant difference in any SPM due to dexamethasone over the duration of the study. There was a fall in 17-HDHA between baseline and 24 h in both the dexamethasone and saline groups (P = 0.003) but no change in the downstream SPM (RvD1, 17R-RvD1 and RvD2) or 18-HEPE and RvE2. Pain score was negatively related to levels of RvE2 measured prior to induction of anaesthesia (rho = -0.2991, P = 0.006) and positively related to BMI (rho = 0.279, P = 0.011). In ordinal logistic regression the odds ratio for RvE2 was 0.931 (CI 0.880, 0.986; P = 0.014); after adjusting for the effect of BMI indicating that an increase in RvE2 of 1 pg/ml would result in a 6.9 % fall in pain score. Allocation to a dexamethasone group did not influence the pain score or the relationship between RvE2 and pain score.

CONCLUSION

Dexamethasone administered as an anti-emetic does not affect plasma SPM levels. An elevated RvE2 level prior to surgery is predictive of a lower perceived pain score post-anaesthesia.