The effect of clonidine on the minimum local analgesic concentration of epidural ropivacaine during labor

Circadian Variation in the Median Effective Dose of Epidural Ropivacaine for Labor Analgesia

Background: Labor pain perception has been demonstrated to exhibit a circadian rhythm with lower pain scores during the day compared with the night. This study aimed to determine and compare the median effective dose (ED₅₀) of ropivacaine in parturients having epidural labor analgesia during the day vs. during the night.

Methods: The study group consisted of 60 nulliparous healthy parturients who were assigned to one of two groups according to the time they requested labor analgesia: Day Group (7:01 am to 7:00 pm) and Night Group (7:01 pm to 7:00 am). A bolus of.15% ropivacaine was administered epidurally and effective analgesia was defined as the attainment of a visual analog scale (VAS) pain score ≤ 10 mm within 30 min. The dose of ropivacaine for the first parturient in each group was 18 mg. The dose for each subsequent parturient was varied with increments or decrements of 3 mg based on the response of the previous subject. The ED₅₀ was calculated using up-down sequential analysis. Probit regression was used to estimate the relative mean potency of ropivacaine between groups.

Results: The ED₅₀ (mean [95% CI]) of ropivacaine was lower in the Day Group (17.9 [16.5–19.4] mg) than in the Night Group (20.9 [19.2–22.7] mg) (P = 0.003). The estimate of relative potency for ropivacaine for the Night Group vs. the Day Group was 0.85 (95% CI:0.56–0.98).

Conclusions: Under the conditions of this study, the dose requirement for epidural ropivacaine for labor analgesia was ~ 15% greater during the night than during the day.

Clinical Trials Registration: Chinese Clinical Trial Registry (No.: ChiCTR1900025269. http://www.chictr.org.cn/showprojen.aspx?proj=36993).

Effect of epidural clonidine on minimum local anesthetic concentration (ED50) of levobupivacaine for caudal block in children

BACKGROUND

Clonidine has the potential to significantly prolong the duration of caudal epidural anesthesia. We investigated the effect of the addition of clonidine to the MLAC of levobupivacaine in a randomized controlled dose-response trial.

METHODS

A group of 120 children aged <6 years of age received caudal anesthesia with levobupivacaine and 1, 2, or 3 μg·kg(-1) of clonidine. The MLAC was determined according to a Dixon-Massey protocol. The primary outcome was effective surgical anesthesia. Secondary outcomes were the duration of postoperative analgesia, postoperative pain scores, clonidine side effects, and time to hospital discharge.

RESULTS

The MLAC of caudal levobupivacaine was 0.106%, 0.077%, and 0.035% with 1, 2, and 3 μg·kg(-1) of clonidine, respectively. There were significant dose-dependent increases in median duration of analgesia. The incidence of delayed discharge, somnolence, and PONV was significantly increased in the 3 μg·kg(-1) of clonidine group.

CONCLUSIONS

Clonidine produces a local anesthetic sparing effect with a dose-dependent decrease in levobupivacaine MLAC for caudal anesthesia. In addition, there is a dose-dependent prolongation of postoperative analgesia following lower abdominal surgery in children. A dose of 2 μg·kg(-1) of clonidine provides the optimum balance between improved analgesia and minimal side effects.

Ropivacaine: a review of its use in regional anaesthesia and acute pain management

Ropivacaine (Naropin) is the pure S(-)-enantiomer of propivacaine, and is a long-acting amide local anaesthetic agent, eliciting nerve block via reversible inhibition of sodium ion influx in nerve fibres. Ropivacaine is a well tolerated regional anaesthetic effective for surgical anaesthesia as well as the relief of postoperative and labour pain. The efficacy of ropivacaine is similar to that of bupivacaine and levobupivacaine for peripheral nerve blocks and, although it may be slightly less potent than bupivacaine when administered epidurally or intrathecally, equi-effective doses have been established. Clinically adequate doses of ropivacaine appear to be associated with a lower incidence or grade of motor block than bupivacaine. Thus ropivacaine, with its efficacy, lower propensity for motor block and reduced potential for CNS toxicity and cardiotoxicity, appears to be an important option for regional anaesthesia and for the management of postoperative and labour pain.