Obesity decreases the EC50 of epidural ropivacaine when combined with dexmedetomidine for labor analgesia

Abstract

ABSTRACT Objectives This study aims to estimate the EC50 of ropivacaine when co-administered with dexmedetomidine for epidural labor analgesia in antepartum obese and non-obese parturients. Methods Sixty parturients scheduled for epidural labor analgesia were enrolled and divided into antepartum obesity (AO) and control (CON) groups, according to their body mass index at labor. Both groups received 0.5 µg/mL dexmedetomidine with ropivacaine as anesthetics. The concentration of ropivacaine was initially set at 0.125% and varied by 0.01% according to the up‐and‐down rule for sequential allocation. Hemodynamic parameters were monitored and pain intensity was assessed using a visual analog scale. Results When co-administered with dexmedetomidine, the EC50 of ropivacaine was 0.095% (95% confidence interval [CI]: 0.090–0.100%) and 0.070% (95% CI: 0.062–0.076%) in CON and AO groups, respectively. There was a significant difference between the two groups (P < 0.001). EC95 values of ropivacaine were 0.084% (95% CI: 0.077–0.122%) and 0.106% (95% CI: 0.101–0.128%) in AO and CON groups, respectively. Conclusion Patients with antepartum obese may require decreased ropivacaine concentration for epidural labor analgesia when co-administered with 0.5 µg/mL dexmedetomidine.