title: Dose-response of ropivacaine administered caudally to children undergoing surgical procedures under sedation with midazolam.
abstract: 1. In a double-blind randomized controlled design, 50 children were allocated to receive bupivacaine 0.25% or ropivacaine 0.25%, 0.32%, 0.40% or 0.50% by caudal block. 2. Caudal block was performed after induction of anaesthesia with 2-5% sevoflurane, atropine 10 microg/kg and midazolam 100-300 microg/kg. During the surgical procedure, patients were maintained under spontaneous ventilation and no intravenous or inhalatory anaesthetic agent was administered. For transoperative sedation, midazolam 100-300 microg/kg was administered every 0.5-1.0 h. Transoperative cardiovascular response, postoperative analgesia and local and systemic complications were evaluated. 3. Groups were similar (P > 0.05) in sex, age, weight and in the time elapsed from caudal block to the beginning of the surgical procedure. The surgical time was significantly lower in the ropivacaine 0.25% group. The duration of analgesia was 24 h with ropivacaine 0.25% and approximately 10 h in the other four groups (P < 0.001). Linear regression analysis revealed a significant relationship between the postoperative analgesic period produced by ropivacaine and the surgical time (r = -0.48, two-sided P = 0.002). Systolic and diastolic blood pressures remained in the physiologically normal range for the duration of the transoperative period. Vomiting was present in only one patient receiving ropivacaine 0.50%. 4. In children, the duration of analgesia produced by caudal block with ropivacaine may be affected by surgical time. At surgical times of 0.5-1 h, ropivacaine 0.25% produced at least 24 h postoperative analgesia. At similar surgical times, ropivacaine 0.32%, 0.40% and 0.50% produced similar analgesic times to bupivacaine 0.25%.
authors.affiliation: Hospital de Gineco-Pediatría no. 48, IMSS, Guanajuato, Mexico DF, Mexico.
authors.forename: F Tonatiu
authors.initials: FT
authors.lastname: Aguirre-Garay
authors.forename: Rosario
authors.initials: R
authors.lastname: García
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Nava-Ocampo
mesh_terms: D000577:Amides / Q000008:administration & dosage; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000008:administration & dosage; D002045:Bupivacaine / Q000008:administration & dosage; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives; D016014:Linear Models; D008297:Male; D008874:Midazolam; D010147:Pain Measurement / Q000187:drug effects; D000077212:Ropivacaine
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D006993:Hypnotics and Sedatives; D000077212:Ropivacaine; D008874:Midazolam; D002045:Bupivacaine