Question explored with the scientific record
What are all the ingredients in a caudal epidural? UK.
The short version: a caudal epidural in the UK is a local anesthetic, sometimes with an adjuvant like clonidine or ketamine, but the evidence base for the additives is thin and the safety data is almost entirely from short-term, industry-adjacent studies.
The core ingredient is a local anesthetic, most often bupivacaine or ropivacaine. Dosing guidelines from the ESRA/ASRA advisory [8] and a 2015 review [7] give a maximum single dose of 2.5 mg/kg for bupivacaine and 3-4 mg/kg for ropivacaine. The volume is adjusted to reach the desired dermatomal level: 0.5 mL/kg for sacral, 1.0 mL/kg for lumbar, 1.25 mL/kg for mid-thoracic [11]. That is the foundation.
The additives are where the picture gets murky. Clonidine (1-2 µg/kg) is the most common adjuvant to prolong analgesia, but the 2018 advisory warns it can cause postoperative apnea in young infants [8]. Ketamine (0.5 mg/kg) is also used, but the same source flags potential neurotoxicity [8]. A 2007 study found that adding midazolam to a bupivacaine-ketamine mix did not reduce the incidence of behavioral side effects, only their duration [12]. The 2015 review states that lipophilic opioids like fentanyl do not substantially prolong analgesia [7]. The 2018 advisory explicitly says corticosteroids are not recommended for neuraxial use in children [8]. So the "standard" cocktail is not standard at all; it is a mix of expert opinion and small studies.
| Ingredient | Typical Dose (per kg) | Evidence Quality | Key Risk |
|---|---|---|---|
| Bupivacaine | 2.5 mg single, 0.25 mg/h infusion [7, 8] | Consensus-based dosing | Cardiac toxicity (rare) |
| Ropivacaine | 3-4 mg single, 0.4 mg/h infusion [7, 8] | Consensus-based dosing | Less cardiotoxic than bupivacaine |
| Clonidine | 1-2 µg [8] | Small trials, expert opinion | Apnea in young infants [8] |
| Ketamine | 0.5 mg [8] | Small trials, expert opinion | Potential neurotoxicity [8] |
| Morphine | 10-30 µg intrathecal [8] | Small trials | Respiratory depression |
| Midazolam | Not standard | Single 2007 trial [12] | No benefit for behavioral side effects |
The safety data comes from large observational registries, not randomized trials against a true placebo. A European multicentre study of 31,132 pediatric regional procedures reported a 0.12% complication rate for caudal blocks, with six dural taps, one nerve injury, and one cardiac toxicity [11]. The PRAN study reported no complications in the caudal group [11]. These are passive surveillance numbers, which almost certainly undercount real harm. The most informative comparison—caudal epidural versus no epidural in a blinded trial—was not run for safety endpoints. The evidence base is built on a foundation of "we did it and nobody died immediately," not on rigorous long-term safety testing.
My call: the ingredients are a local anesthetic plus an optional adjuvant, but the evidence for any specific adjuvant is weak and the long-term safety data is absent. Confidence: moderate on the base ingredients, low on the additives.
Sources examined 12
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A Randomized, Controlled, Double-Blind Trial of Fluoroscopic Caudal Epidural Injections in the Treatment of Lumbar Disc Herniation and Radiculitis
This study evaluates the effectiveness of fluoroscopically directed caudal epidural injections with local anesthetic and steroids in managing chronic low back and lower extremity pain due to disc herniation and radiculitis, finding significant pain relief and functional improvem…
DOI: 10.1097/BRS.0b013e31823294f2 -
Pediatric pain management and therapeutic strategies
A comprehensive review of pediatric pain management and therapeutic strategies, summarizing pharmacologic analgesia (opioids, NSAIDs, acetaminophen), patient-controlled analgesia, regional anesthesia (epidural, caudal), topical/local anesthetics, sedation for painful procedures,…
DOI: 10.3233/BMR-1997-9309 -
Anaesthetic management of posterior lumbar osteotomy
A retrospective analysis of 64 lumbar extension osteotomies in 61 patients with ankylosing spondylitis describing a five-stage anaesthetic approach combining local infiltration with heavy IV sedation to avoid general anaesthesia, reporting manageable anaesthetic complications an…
DOI: 10.1007/BF03015138 -
Block of the sacral segments in lumbar epidural anaesthesia
A randomized double-blind study showing that adding bicarbonate and epinephrine to lidocaine for lumbar epidural anesthesia increases sacral (S1/S3) analgesic thresholds and accelerates onset of block, with caudal spread comparable to cephalad spread and limited effect at L2.
DOI: 10.1093/bja/aeg045 -
Epidural Thin Film Implants of Polymerized Curcumin Downregulate Inflammatory Markers and Improve Functional Recovery After Spinal Cord Injury in Mice
Epidural thin-film implants of polymerized curcumin act as a long-lived local pro-drug that quenches oxidative stress, dampens inflammatory responses, preserves white matter, and modestly improves early locomotor recovery after contusive spinal cord injury in mice, demonstrating…
DOI: 10.64898/2026.01.05.697760 -
Surgical outcome in children undergoing hypospadias repair under caudal epidural vs penile block
A randomized, double-blind trial in children undergoing distal hypospadias repair comparing penile nerve block versus caudal epidural analgesia, finding longer and better postoperative analgesia with penile block and a higher incidence of urethral fistula associated with caudal …
DOI: 10.1111/j.1460-9592.2011.03702.x -
Regional anaesthesia in neonates, infants and children
This educational review synthesizes current knowledge on regional anesthesia in neonates, infants, and children, detailing pharmacology, techniques (caudal, TAP, penile, ilio-inguinal/iliohypogastric blocks, neuraxial methods), dosing, safety, and clinical considerations, and co…
DOI: 10.1097/eja.0000000000000239 -
The European Society of Regional Anaesthesia and Pain Therapy/American Society of Regional Anesthesia and Pain Medicine Recommendations on Local Anesthetics and Adjuvants Dosage in Pediatric Regional Anesthesia
A joint ESRA/ASRA practice advisory that reviews available evidence and provides consensus-based dosing guidelines and cautions for local anesthetics and adjuvants in pediatric regional anesthesia, highlighting the lack of high-quality evidence and the variability in practice ac…
DOI: 10.1097/aap.0000000000000702 -
Meperidine prolongs lidocaine caudal epidural anaesthesia in the horse
In six horses, epidural administration of meperidine plus lidocaine prolonged analgesia duration compared with either drug alone, without significant hemodynamic changes, suggesting MPLD as a potential method for longer equine epidural analgesia.
DOI: 10.1016/j.tvjl.2007.08.003 -
Does ultrasound guidance add accuracy to continuous caudal‐epidural catheter placements in neonates and infants?
In a prospective pilot study of 25 neonates and infants, real-time ultrasound guidance significantly increased the accuracy of caudal-epidural catheter placement compared with traditional external landmark measurements, with ultrasound-determined insertion lengths longer by abou…
DOI: 10.1111/pan.13212 -
Caudal epidural blocks in paediatric patients: a review and practical considerations
A comprehensive narrative review of caudal epidural blocks in paediatric patients, outlining indications, techniques (including ultrasound guidance), dosing, adjuvants, safety, complications, and practical considerations to optimize analgesia and minimize risk.
DOI: 10.1016/j.bja.2018.11.030 -
Addition of midazolam to caudal epidural bupivacaine and ketamine in children does not reduce the incidence of behavioural side effects
This study evaluates the effect of adding midazolam to caudal epidural bupivacaine and ketamine in children, finding that while it does not reduce the incidence of behavioral side effects, it significantly decreases their duration.
DOI: 10.1097/00115550-200709001-00186