Literature Review
The Dose of Caudal Epidural Analgesia and Duration of Postoperative Analgesia.
Schrock SR & Jones MB. Paediatric Anaesthesia 13: 403-408, 2003
Review: The purpose of this investigation was to determine the optimal volume to be administered for a single-shot caudal anesthetic. In a randomized, blinded, controlled fashion, 54 children between the ages of 1 and 6 years with ASA status I and II, scheduled for inguinal hernia repair were enrolled. All children received premedication with midazolam 0.5 mg/kg orally and an inhalation induction with nitrous oxide in oxygen and halothane. All children were administered a caudal anesthetic with 0.175% bupivacaine with epinephrine 5 mcg/ml. The children were divided into three groups: Group 1 received 0.7 ml/kg of local anesthetic, Group 2 received 1 ml/kg, and Group 3 received 1.3 ml/kg. Patients who were included in the study received no other intraoperative analgesics. Duration of analgesia was determined by the time to first analgesic upon either recovery nurse or parental request. CHEOPS pain score was assessed for all children.
Results: 51 children were included in the results as 2 children did not receive caudal anesthetics because of technical difficulty, and one child was lost to follow up. The 3 groups did not differ with respect to age, weight, or gender. The duration of analgesia was not statistically significant among the groups with Group 1 requiring first analgesic in 4.2 hours, Group 2 in 3.6 hours, and Group 3 in 4.85 hours. Times to voiding, ambulation and discharge also did not differ significantly among the groups.
Comments: Concentration of local anesthetic is clearly associated with a prolonged duration of analgesia, but may also be associated with motor block postoperatively. It has been thought that this could be avoided by using lower concentrations in higher volumes. This is the first study that isolates volume as a factor in duration of analgesia by administering one single concentration of local anesthetic in different volumes. Conventional wisdom has always directed the practitioner to the thought that an increased volume of local anesthetic should provide an increased duration because the regression of the caudal anesthetic should be cephalad to caudad. Caudal anesthetics using these more dilute local anesthetics, however, may not undergo this same pattern of regression. This study by Schrock and Jones has provided additional information on the effectiveness, or the actual ineffectiveness of increasing the volume of a dilute local anesthetic with a recommendation that the lower volumes be used for the above indication. A follow up study using a higher concentration would be of interest.
Reviewed by: Allison K. Ross, MD
References
Gunter et al. Optimal concentration of bupivacaine for combined caudal-general anesthesia in children. Anesthesiology 75: 57-61, 1991
Fisher et al. Postoperative voiding interval and duration of analgesia following peripheral or caudal nerve blocks in children. Anesth Analg 76: 173-177, 1993
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