How different doses of epidural ropivacaine affect pain relief during labor

The ED50 of ropivacaine for initiating epidural analgesia in early labor is 18.4 mg (95% confidence interval, 13.4-25.4 mg).

• A sigmoid dose-response curve was established with a linear regression coefficient of 0.84.
• The effectiveness of different doses was evaluated based on a 50% or greater reduction in pain scores.
• Time to onset of analgesia and duration of analgesia were not significantly affected by the dose of ropivacaine.
• The upper level of sensory block increased with higher doses of ropivacaine (P < 0.01).
• No significant differences were found in the incidence of motor block across the different doses.

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