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

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.

KEYWORDS:

• Dexmedetomidine
• labor analgesia
• obesity
• median effective concentration
• ropivacaine

Article highlights

• Obesity may affect the optimal concentration of epidural ropivacaine for labor analgesia.

• Up-down sequential allocation methodology was applied to study the EC50 of epidural ropivacaine for antepartum obese and non-obese parturient.

• EC50 of ropivacaine in obesity group was 0.070% and 0.095% in BMI normal group.

• EC95 of ropivacaine in obesity group was 0.084% and 0.106% in BMI normal group.

• Obese parturient require less local anesthetic to achieve an adequate level of labor analgesia.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

The study was supported by Institutional Research Grants from Chongqing Health Center for Women and Children (No. 2019YJMS02 and 2019YJMS07).