What are the typical doses for epidural and spinal anesthesia, including bupivacaine (local anesthetic) and fentanyl (opioid analgesic)?

Epidural and Spinal Anesthesia Dosing

Intrathecal (Spinal) Anesthesia Dosing

For intrathecal labor analgesia after accidental dural puncture, initiate with bupivacaine 1.5-2.5 mg combined with fentanyl 5-20 µg, then maintain with a continuous infusion of bupivacaine 0.0417-0.1% plus fentanyl 2-2.5 µg/mL at 1-3 mL/hour. 1

Initial Bolus Dosing for Labor Analgesia

• Bupivacaine: 1.25-5 mg (most commonly 1.5-2.5 mg) 1
• Fentanyl: 5-20 µg (most commonly 12.5-25 µg) 1
• Alternative opioid: Sufentanil 2.5-7.5 µg may replace fentanyl 1

Maintenance Infusion for Labor

• Bupivacaine concentration: 0.0417-0.1% 1
• Fentanyl concentration: 2-2.5 µg/mL 1
• Infusion rate: 1-3 mL/hour 1
• Patient-controlled boluses: 0.5-1 mL every 20-30 minutes if needed 1
• Breakthrough pain management: 1-2 mL of maintenance solution administered by clinician 1

Cesarean Section via Intrathecal Catheter

• Initial opioid bolus: Fentanyl 15-20 µg plus morphine 0.25-0.3 mg 2
• Incremental local anesthetic: Bupivacaine 1.25-2.5 mg boluses every 3 minutes until T4 sensory level achieved 3, 2
• Total dose range: 7.5-25 mg bupivacaine (median 8.8-15 mg) 3, 2
• Critical safety measure: Never exceed 2.5 mg increments to minimize high block risk 3

Standard Single-Shot Spinal for Cesarean

• Hyperbaric bupivacaine 0.5%: 10-15 mg (2-3 mL) to achieve T4 level 2
• Adjuvant opioid: Morphine ≤100 µg or diamorphine 300 µg 2

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Epidural Anesthesia Dosing

For epidural test dosing to detect intrathecal catheter misplacement, use no more than 10 mg bupivacaine equivalent, as recommended by the Royal College of Anaesthetists to minimize risk of total spinal anesthesia while producing clinically evident sensory, motor, or autonomic effects. 1

Test Dose Guidelines

• Maximum safe test dose: 10 mg bupivacaine or equivalent 1
• Rationale: This dose produces detectable sensory/motor/autonomic changes if intrathecal, while minimizing high or total spinal risk 1
• Alternative validated dose: 8 mg bupivacaine showed ≥80% sensitivity and positive predictive value 1

Initial Loading Dose for Epidural Analgesia

Lumbar epidural in adults:

• Bupivacaine 0.25%: 0.5 mL/kg (maximum 15 mL) 3, 4, 5
• This equals: 12.5-37.5 mg bupivacaine depending on patient weight 3, 4

Thoracic epidural in adults:

• Bupivacaine 0.25%: 0.2-0.3 mL/kg (maximum 10 mL) 3, 4

Pediatric populations:

• Maximum dose: 2.5 mg/kg (1 mL/kg of 0.25% bupivacaine) 3, 4
• Caudal block: 1.0 mL/kg of 0.25% bupivacaine 3, 4

Epidural Maintenance Infusion

• Bupivacaine concentration: 0.1% (1 mg/mL) 6, 7
• Fentanyl concentration: 2-3 µg/mL 8, 6, 7
• Infusion rate: 5-10 mL/hour 6, 7
• Patient-controlled boluses: 5 mL with 15-minute lockout 6

Maximum Dosing Limits

• Single dose with epinephrine: Up to 225 mg bupivacaine 5
• Single dose without epinephrine: Up to 175 mg bupivacaine 5
• Maximum 24-hour dose: 400 mg bupivacaine 5
• Repeat dosing interval: Every 3 hours minimum 5

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Critical Safety Considerations

Incremental Dosing Technique

• Always use fractional doses: Administer epidural bupivacaine in 3-5 mL increments 5
• Allow sufficient time between doses: To detect signs of intravascular or intrathecal injection 5
• Obstetric epidural: Use only 0.25% or 0.5% concentrations; 0.75% is contraindicated 5
• Obstetric dosing limit: 50-100 mg per dosing interval for 0.5% solution 5

Special Population Adjustments

• Elderly and debilitated patients: Reduce all doses 5
• Cardiac or hepatic disease: Reduce all doses 5
• Patients <40 kg: Calculate doses carefully 3, 4
• Obese patients: Use ideal body weight for calculations 3, 4

Common Pitfalls to Avoid

• Never use 0.75% bupivacaine for obstetric anesthesia due to cardiac toxicity risk 5
• Never use preservative-containing vials for neuraxial techniques 5
• Do not omit test doses when using epidural catheters, especially in obstetrics 5
• Avoid rapid injection of large volumes; always use incremental technique 5
• Monitor for hypotension more vigilantly with intrathecal catheters (25.6% incidence vs 3.8% with epidural) 1

Monitoring Requirements

• Standard monitoring: No additional cardiovascular or respiratory monitoring beyond routine epidural practice is typically required for intrathecal catheters 1
• Exception: If intrathecal morphine used, assess respiratory rate and sedation hourly for 12 hours, then every 2 hours for next 12 hours 1