SummaryProbit analysis was used to predict the median effective concentration (EC 50 ) and the 95% effective concentration (EC 95 ) values of levobupivacaine for caudal analgesia in children at equal volumes of injectate. Sixty children scheduled for inguinal herniorrhaphy were recruited. Anaesthesia was induced with sevofurane and nitrous oxide. Then caudal block (total volume of local anaesthetic 1 ml.kg )1 ) was performed. Patients randomly received one of six concentrations (0.08%, 0.10%, 0.12%, 0.14%, 0.16% or 0.18%) of levobupivacaine. Thereafter, inhalational anaesthetics were discontinued and intravenous midazolam 0.1 mg.kg )1 was administered to maintain sedation. The effective caudal analgesia was defined as an absence of gross movements and a haemodynamic (heart rate or blood pressure) reaction < 20% compared with baseline in response to surgical incision. Our data indicated that the EC 50 and EC 95 values of levobupivacaine for caudal analgesia were 0.109% (95% confidence intervals 0.098-0.120%) and 0.151% (95% confidence intervals 0.135-0.193%) when using the same volume (1 ml.kg )1 ), respectively. Caudal anaesthesia in children is usually performed after an inhaled or intravenous (i.v.) induction and is a useful adjunct for providing postoperative analgesia after genital, lower abdominal, and lower limb operations. It can reduce the amount of inhaled and intravenous anaesthetic required, attenuate the stress response to surgery, facilitate a rapid and smooth recovery, and provide good immediate postoperative analgesia. Levobupivacaine, the S-enantiomer of bupivacaine, has been promoted as an alternative to (with less cardiotoxicity than) racemic bupivacaine [1,2]. Despite extensive use in children [3][4][5], the optimal concentration of levobupivacaine in caudal blockade remains to be established. The minimum local analgesic concentration (MLAC) has been developed as a useful clinical measure of epidural analgesia [6,7]. Unfortunately, MLAC studies only describe one point of the dose-response curve, the effective dose in 50% of the population and do not provide information about the shape or slope of the curve. Indeed, the 95% effective concentration (EC 95 ) would often be more clinically relevant. We hypothesised that the clinical effect of levobupivacaine in caudal analgesia in children varied with the dose used (at equal volumes of injectate), and the purpose of our study was to describe the full dose-response relation of levobupivacaine in this context. MethodsAfter approval by the Hospital Research Ethics Committee and informed written consent from parents, sixty ASA status I children, aged 1-3 years scheduled for elective inguinal herniorrhaphy were enrolled. Children with neurological, neuromuscular, psychiatric or blood clotting disorders or with a known allergy to local anaesthetics were excluded.All children were starved > 6 h but not premedicated. In the operating room, the patients were monitored with electrocardiography, pulse oximetry, heart rate (HR) respiratory rate (RR), and no...

(Anesth Analg. 2018;127:171–178) A major limitation of spinal anesthesia is that the duration of the anesthetic may not be adequate in the event of a prolonged surgery. Bupivacaine without an adjuvant provides ∼120 minutes of surgical anesthesia. Epinephrine added to lidocaine or tetracaine can increase the block’s duration as much as 2-fold. However, less is known about the prolongation of spinal block when epinephrine is added to bupivacaine. In the present study, the authors evaluated whether the addition of subarachnoid epinephrine to bupivacaine and morphine would prolong the duration of surgical anesthesia for repeat cesarean delivery as measured by the time to T-10 regression or activation of the epidural for patient comfort.