Effects of dexamethasone on the EC50 of remifentanil combined with dexmedetomidine achieving analgesia during pancreatic extracorporeal shockwave lithotripsy: a prospective, randomized and controlled study.

Background: In addition to their classic genomic effects, glucocorticoids also manifest rapid non genomic effects. We speculate that dexamethasone has the potential prompt onset of analgesic effects. The objective of this study is to investigate the influence of a single preoperative dose of dexamethasone on the half maximal effective concentration (EC50) of remifentanil when combined with dexmedetomidine for pain relief during pancreatic extracorporeal shockwave lithotripsy (P-ESWL).
Methods: A total of 60 patients undergoing P-ESWL were enrolled and randomized at 1:1 ratio into the dexamethasone (DXM) group and the placebo group. Before anesthesia induction, patients in DXM group received an intravenous injection of 8 mg dexamethasone, while subjects in placebo group received an equal dose of physiological saline. Monitored anesthesia care (MAC) was performed based on remifentanil in combination with dexmedetomidine. Remifentanil was administered by TCI with an initial target concentration of 2.5 µg/mL for both groups. A positive response was defined as that VAS score > 3 by the patient at any time during the procedure. Subsequent target concentrations were adjusted by Dixon up-down sequential method, where dose modifications were performed by 0.3 ng/mL intervals, based on the response of the previous patient. The EC50 of remifentanil for pain relief during P-ESWL treatment was calculated using Dixon's up-and-down method. Hemodynamic variables, oxygen saturation and adverse events were also recorded.
Results: Dixon up-and-down method revealed that the EC50 of remifentanil was significantly higher in placebo group (2.65 ± 0.28 ng/mL) than in DXM group (2.02 ± 0.23 ng/ml) (P < 0.001). Hemodynamic parameter exhibited a significant decrease in mean arterial pressure (MAP) and heart rate (HR) before and after induction in placebo group; however, data of the two groups were comparable (P>0.05). Less adverse events occurred in DXM group, including the incidence of postoperative nausea and vomiting (PONV) and analgesia requirement with in the first 24 h following the procedure at ward.
Conclusion: Dexamethasone exerted analgesic effects with a rapid onset, and patients received dexamethasone 8 mg preoperative had a lower required EC50 of remifentanil during P-ESWL. It is also associated with reduced PONV in addition to reduced postoperative analgesic consumption in the first postoperative 24 h.
Trial Registration: Registered in the Chinese Clinical Trial Registry (ChiCTR2300078171) on 30/11/2023.
(© 2024. The Author(s).)