Intravenous Dexamethasone to Prolong Caudal Block Analgesia in Children Undergoing Hip Surgery

This prospective, randomized, double-blind, placebo-controlled trial was conducted in the Department of Anesthesiology and Intensive Care of the Children's Hospital Bechir Hamza of Tunis between September 2019 and December 2020, after approval by the local ethics committee and written informed consent from a parent.

Children aged 6 months to 9 years, weighing 20 kg or less, ASA physical status I or II, scheduled for unilateral or bilateral surgery for developmental dysplasia of the hip, were eligible.

Anesthesia was induced by inhalation of sevoflurane 8% in a 50% nitrous oxide/oxygen mixture, followed by propofol 2 mg/kg and fentanyl 3 µg/kg after peripheral venous access. The trachea was intubated, ventilation was controlled (tidal volume 7 ml/kg, end-tidal CO2 target 35 mmHg) and anesthesia was maintained with sevoflurane at 1 MAC.

At induction, children were randomized with the Random Allocation software to receive either dexamethasone 0.5 mg/kg (0.5 ml/kg of a 1 mg/ml solution, maximum 10 mg) intravenously (Group D) or the same volume of normal saline (Group P). The physician administering the study solution, the child and the parents were blinded to group allocation.

A single-shot caudal block was then performed in the lateral position with a 22 G, 30 mm short-bevel caudal needle, injecting 1 ml/kg of plain bupivacaine 0.25% after negative aspiration. Surgical incision took place at least 10 minutes after the block. Block failure was defined as an increase of more than 20% in heart rate and/or blood pressure from baseline within 20 minutes of incision; these children received fentanyl 2 µg/kg and were excluded.

No analgesic was given routinely after surgery. Pain was assessed with the CHEOPS score at awakening, 30 minutes and 1, 2, 3, 4, 8, 12 and 24 hours after surgery. A CHEOPS score of 7 or more triggered intravenous paracetamol 15 mg/kg; if the score remained above 7 after 30 minutes, nalbuphine 0.2 mg/kg was infused over 20 minutes.

The primary outcome was the time to first analgesic request, from caudal block to first analgesic administration. Secondary outcomes were the number and type of analgesics given, the incidence of postoperative nausea and vomiting, and perioperative anesthetic or surgical adverse events.

Sample size: based on a previous trial in children undergoing orchidopexy (time to first analgesic 8.33 ± 0.98 h with dexamethasone versus 6.00 ± 1.15 h with placebo), 26 children per group were required (two-sided alpha 5%, beta 5%). Data were analyzed with IBM SPSS 23 using Pearson's chi-square test, Student's t-test or the Mann-Whitney test as appropriate, and Kaplan-Meier survival analysis for the primary outcome. A p-value below 0.05 was considered significant.