What dose of hyperbaric bupivacaine (0.5%) should be used for a single‑shot spinal anesthesia in a healthy 10‑year‑old, 32 kg child undergoing open reduction and internal fixation of the ankle and tibia?

Spinal Anesthesia Dosing for 10-Year-Old, 32 kg Child Undergoing ORIF Ankle and Tibia

For this 10-year-old, 32 kg child undergoing lower extremity orthopedic surgery, administer 0.5 mg/kg of hyperbaric bupivacaine 0.5%, which equals 16 mg or 3.2 mL total dose. 1

Dosing Algorithm for Pediatric Spinal Anesthesia

Age-Based Dosing Strategy

• Children older than 1 year should receive 0.5 mg/kg of hyperbaric bupivacaine 0.5% for spinal anesthesia, as recommended by the joint ASRA/ESRA guidelines 1
• For this 32 kg patient, the calculation is: 0.5 mg/kg × 32 kg = 16 mg total dose (3.2 mL of 0.5% hyperbaric bupivacaine) 1
• This dose is appropriate for lower extremity orthopedic procedures including ORIF of ankle and tibia 2, 1

Evidence Supporting This Dosing

• A large prospective study of 1,132 pediatric patients (ages 6 months to 14 years) demonstrated that 0.2 mg/kg of 0.5% hyperbaric bupivacaine provided adequate anesthesia for lower body surgery, with only 27 patients requiring supplementation 2
• However, the ASRA/ESRA consensus guidelines recommend the higher dose of 0.5 mg/kg for children over 1 year to ensure adequate surgical anesthesia 1
• The higher guideline-recommended dose (0.5 mg/kg) should be used rather than the lower research dose (0.2 mg/kg) to minimize the risk of inadequate block for this major orthopedic procedure 1

Technical Considerations

Baricity Selection

• Hyperbaric bupivacaine (in 8% glucose) is preferred over isobaric solutions because it provides a higher success rate (96% vs 82%) in pediatric patients 3
• Both 0.9% and 8% glucose solutions produce similar block characteristics, but hyperbaric solutions offer more predictable spread 4, 3

Expected Block Characteristics

• The median highest sensory level achieved is typically T3-T4, which is adequate for lower extremity surgery 2, 3
• Duration of sensory block is approximately 80 minutes (range 30-190 minutes) with two-segment regression 3
• Motor block intensity correlates with adequate sensory blockade 3

Sedation Protocol

• Administer sedation with midazolam, propofol, or thiopental during the procedure while maintaining spontaneous ventilation 2
• Avoid inhalational anesthetics as they are not necessary with adequate spinal blockade 2

Safety Profile and Monitoring

Cardiovascular Stability

• Hypotension is rare in children under 10 years (incidence of only 9/942 or <1% in the large pediatric series) 2
• For this 10-year-old, the risk remains low but have atropine and vasopressors immediately available 2, 3
• Maintain standard monitoring including continuous pulse oximetry, heart rate, blood pressure, and SpO₂ 5

Neurological Complications

• Post-dural puncture headache incidence is very low (5/1,132 or 0.4%) in pediatric patients 2
• Backache occurs in less than 1% of cases 2
• No serious neurological complications have been reported with this dosing regimen 2

Common Pitfalls to Avoid

• Do not use the adult dose of 1 mg/kg in children over 1 year, as this exceeds recommended pediatric dosing and increases toxicity risk without improving block quality 1
• Do not underdose by using 0.2 mg/kg for major orthopedic procedures, as this may result in inadequate anesthesia requiring supplementation or conversion to general anesthesia 2, 1
• Ensure proper positioning (lateral decubitus) during injection to optimize spread of hyperbaric solution 3
• Use appropriate needle size (24-27 gauge pediatric spinal needle) to minimize trauma and post-dural puncture headache risk 3

Backup Plan for Inadequate Block

• Have fentanyl 1-2 mcg/kg IV available for breakthrough pain if the block is insufficient 5
• Consider supplemental sedation rather than immediate conversion to general anesthesia if the block is adequate but the child is anxious 2
• If complete block failure occurs (rare with hyperbaric solution), convert to general anesthesia 3