Determination of the median effective dose ( ED 50 ) of spinal chloroprocaine in labour analgesia

Summary The primary goal of this study was to determine the median effective dose ( ED 50 ) of spinal chloroprocaine for labour analgesia. Thirty‐eight parturients requesting neuraxial analgesia were enrolled. Doses of 1% chloroprocaine were determined by the technique of up–down sequential allocation, with an initial dose of 20 mg and steps of 2 mg. The chloroprocaine spinal dose was given as the spinal component of a combined spinal‐epidural, which was then supplemented with an epidural dose of 7.5 μg sufentanil in 7 ml saline. Effective analgesia was defined as a score ≤ 10 mm within 15 min on a 100‐mm visual analogue pain scale. Using the isotonic regression estimator method, the ED 50 of chloroprocaine for the spinal component of a combined spinal‐epidural for labour was calculated to be median (95% CI ) 12.0 (9.3–17.0) mg.