Anesthesiology APPLIED Exam › Pediatric and neonatal

Regional anesthesia in children beyond the caudal

Pediatric and neonatal·~5 min read· Physician-reviewed✓ Sourced · 11

Stem

A 5-year-old boy, 19 kg, otherwise healthy, is having a day-case open left inguinal hernia repair. His parents want him home tonight and hope he avoids opioids. You have induced with sevoflurane and placed a laryngeal mask. The surgeon plans to infiltrate the wound "with plenty of bupivacaine" at the end.

Question

What regional technique will you use, and how do you do it safely in an anesthetized child?

Ideal answer

HeadlineAn ultrasound-guided left ilioinguinal-iliohypogastric block, done asleep, which is the standard in children, with every milligram of local counted against one weight-based ceiling.¹

Ceiling first: bupivacaine 2.5 mg/kg, 47 mg, because the surgeon's infiltration and my block share one total.²
0.15 mL/kg of 0.25% bupivacaine, 3 mL, because that volume covers the nerves between internal oblique and transversus and uses only 7 mg.³

Aspirate, inject slowly in small aliquots, watch the ECG, because under general anesthesia the first sign of toxicity is an arrhythmia or hypotension, not a seizure.¹
Tell the surgeon what is left, so the infiltration stays inside the ceiling.²

Watch for: T-wave or QRS change, ectopy and falling pressure during and for minutes after injection.

Breaking down the answer

Asleep is the norm — in over 100,000 Pediatric Regional Anesthesia Network blocks, complications under general anesthesia were as rare as those reported for awake adult blocks; neurologic complications 0.02%, none permanent.¹ Changes if: a cooperative teenager, who can have it awake.
Low concentrations work — myelination continues to about 12 years, so 0.125–0.2% ropivacaine gives analgesia; 0.5% is rarely needed.¹
Infants need less — below 6 months, low albumin and immature clearance raise free drug, so I cut the weight-based dose by 30–50%.¹ Changes if: a neonate on an infusion, where chloroprocaine is an alternative.⁴
Choosing the block — penile block for circumcision and hypospadias, never with epinephrine;³ TAP or quadratus lumborum for abdominal incisions, the latter spreading T7–L1;¹ caudal for infraumbilical surgery in younger children.
Test dose for neuraxial and catheters — 0.1 mL/kg lidocaine 1.5% with epinephrine 1:200,000;⁵ positive is T-wave amplitude up ≥25%, heart rate up ≥10 bpm or systolic up ≥15 mmHg within 60–90 s.⁶
Catheters — fascial-plane and peripheral infusions run 0.2% ropivacaine or bupivacaine at 0.1–0.3 mg/kg/h;⁴^,7 the commonest problem is a benign failure: dislodgement, occlusion or disconnection.¹

Follow-up question

Despite your warning, the surgeon infiltrates 10 mL of 0.5% bupivacaine. Two minutes later the ECG shows a wide-complex tachycardia at 170 and the blood pressure is 58/30 under sevoflurane. What do you do?

Follow-up answer

HeadlineThis is local anesthetic systemic toxicity, 57 mg against a 47 mg ceiling; I call it, stop surgery and get help and the lipid kit.

I ventilate with 100% oxygen to prevent hypoxemia and acidosis, and give 20% lipid 1.5 mL/kg, about 28 mL over 2–3 minutes, then 0.25 mL/kg/min by pump; I repeat the bolus or double the infusion if he stays unstable.⁸ Epinephrine starts below 1 mcg/kg; no vasopressin, calcium-channel or beta-blockers, or more local.⁸ Amiodarone treats ventricular arrhythmias; propofol only in small doses for a seizure, never while he is unstable. Pulseless, I start PALS. Once stable he is admitted and observed 4–6 hours, not discharged.⁸

Pitfalls that cost points

Treating LAST with standard ACLS doses of epinephrine.⁸
Trusting a negative aspiration: it misses intravascular and intraosseous placement, so neuraxial injections still get a test dose.⁵
Preloading crystalloid before a caudal or spinal in a small child: under about 8 years, hypotension is rare.¹

Rapid-fire

Q: Where does the conus end in a neonate? A: About L3,¹ reaching the adult L1 level by about 1 year;⁹ MRI studies put it there within months of birth.¹⁰

Q: Why do infants need more spinal local per kilogram? A: CSF volume is 4 mL/kg against 2 mL/kg in adults; bupivacaine 1 mg/kg in infants, 0.5 mg/kg over a year.¹^,11

Q: Upper-extremity block dose in a child? A: Bupivacaine or ropivacaine 0.5–1.5 mg/kg.¹¹

Q: An adjuvant to prolong a peripheral block? A: Dexmedetomidine.¹¹

Q: Maximum plain lidocaine? A: 5 mg/kg.²

Numbers to know

Item	Value
Maximum plain dose	Bupivacaine 2.5, lidocaine 5 mg/kg;² ropivacaine 2 mg/kg for a caudal (ESRA/ASRA)⁴
Ilioinguinal-iliohypogastric volume	0.15 mL/kg per side³
Infant under 6 months	Reduce dose 30–50%¹
Catheter infusion	0.1–0.3 mg/kg/h (mg, not mL) of 0.2%⁷
Test dose	0.1 mL/kg lidocaine 1.5% with epinephrine 1:200,000 (epinephrine 0.5 mcg/kg)⁵
Lipid 20% under 70 kg	1.5 mL/kg bolus, 0.25 mL/kg/min, max 12 mL/kg⁸

Sources

1.Regional Anesthesia in Children · OpenAnesthesia (IARS), 2024 · openanesthesia.orgBlocks under GA, PRAN complication data, myelination and concentration, infant dose reduction 30-50%, conus level, LAST presentation under GA, QL vs TAP spread.
2.Transversus Abdominis Plane (TAP) Block case guide · Society for Pediatric Anesthesia, 2024 · www2.pedsanesthesia.orgMaximum plain doses (bupivacaine 2.5, ropivacaine 3, lidocaine 5 mg/kg); communicate block dose to surgeon; TAP volumes 0.1-1 mL/kg per side.
3.Peripheral Nerve Blocks for Urologic Procedures · ASRA Pain Medicine News, 2018 · asra.comIlioinguinal-iliohypogastric volume in children 0.15 mL/kg per side; no epinephrine in penile block.
4.Recomendaciones ESRA/ASRA en anestésicos locales y adyuvantes empleados en la población pediátrica · Revista Electrónica de AnestesiaR (critical summary of the 2018 ESRA/ASRA recommendations), 2019 · dialnet.unirioja.esSpanish-language summary of the full recommendations: peripheral and fascial-plane infusions of 0.2% ropivacaine or bupivacaine at 0.1-0.3 mg/kg per hour (B3); caudal ceiling 2 mg/kg ropivacaine, 2.5 mg/kg bupivacaine (B2); chloroprocaine note.
5.Caudal Anesthesia · OpenAnesthesia (IARS), 2023 · openanesthesia.orgTest dose 0.1 mL/kg lidocaine 1.5% with epinephrine 1:200,000 and its positive criteria.
6.Evaluating T-wave amplitude as a guide for detecting intravascular injection of a test dose in anesthetized children · Anesthesia and Analgesia (Tanaka, Nishikawa), 1999 · europepmc.orgSevoflurane-anesthetized children, epinephrine 0.5 mcg/kg: positive criteria heart rate up >=10 bpm, systolic up >=15 mmHg, T-wave amplitude up >=25%, at about 30, 70 and 20 s; abstract read.
7.Fascial plane blocks in pediatric patients · Journal of Anesthesia, Analgesia and Critical Care (Quiroz, Jacoby, Turan), 2026 · europepmc.orgRestates the 2018 ASRA-ESRA advisory: continuous fascial plane catheters 0.2% ropivacaine or bupivacaine at 0.1-0.3 mg/kg/h (evidence B3); single-shot fascial plane 0.25-0.75 mg/kg; peripheral nerve blocks 0.5-1.5 mg/kg.
8.Checklist for Treatment of Local Anesthetic Systemic Toxicity (LAST) · ASRA Pain Medicine, 2020 · asra.com
9.Pediatric Epidural and Spinal Anesthesia and Analgesia · NYSORA · nysora.comConus at about L3 in neonates and infants, reaching the adult L1 level at about 1 year.
10.Assessment of the levels of termination of the conus medullaris and thecal sac in the pediatric population · Neuroradiology (Blaaza et al.), 2023 · europepmc.org520 MRIs, 1 month to 19 years: no change in conus level with age; prior studies place the final position at 2-5 months after birth.
11.The ESRA/ASRA Recommendations on Local Anesthetics and Adjuvants Dosage in Pediatric Regional Anesthesia · Regional Anesthesia and Pain Medicine (Suresh et al.), 2018 · rapm.bmj.comAbstract only read: spinal bupivacaine 1 mg/kg infants, 0.5 mg/kg over 1 year; upper-extremity blocks 0.5-1.5 mg/kg; dexmedetomidine may prolong peripheral blocks.

Facts on this page were checked against these sources on Oct 23, 2026. Guidelines change; confirm doses against current institutional protocols.