What levobupivacaine concentration and total volume should be used for a bilateral transversus abdominis plane (TAP) block in a typical healthy adult undergoing an elective cesarean section?

Levobupivacaine Dosing for TAP Block After Cesarean Section

For bilateral TAP block after cesarean section, use 0.25% levobupivacaine at a volume of 20 mL per side (total 40 mL, 100 mg total dose). This concentration and volume provides effective analgesia while maintaining plasma levels well below toxic thresholds 1, 2.

Recommended Concentration and Volume

• Concentration: 0.25% levobupivacaine 1, 2, 3
• Volume per side: 20 mL 1, 2, 3
• Total volume: 40 mL (bilateral) 1, 2
• Total dose: 100 mg levobupivacaine 3

Safety Profile

The 0.25% concentration at 20 mL per side has been extensively studied and demonstrates excellent safety margins:

• Peak plasma concentrations occur at approximately 10 minutes post-injection, reaching mean levels of 0.99 μg/mL, with the highest recorded concentration of 1.99 μg/mL—well below the toxic threshold of 2.62 mg/L 3
• Postpartum women have an 80% higher volume of distribution (172 L vs 94.3 L in non-pregnant volunteers), resulting in lower peak concentrations and later time to peak, which provides a greater margin of safety 1
• Maximum safe dose of levobupivacaine is 3.0 mg/kg 4

Clinical Efficacy

This dosing regimen provides:

• Significantly prolonged time to first rescue analgesia request (555 minutes vs 215 minutes without TAP block) 5
• Reduced cumulative morphine consumption within 24 hours (5.3 mg vs 7.7 mg) 5
• Lower pain scores and reduced opioid requirements up to 48 hours postoperatively 6

Important Clinical Context

TAP blocks should only be performed when intrathecal morphine is NOT used, as adding TAP blocks to intrathecal morphine provides no additional analgesic benefit 4, 7. The 2021 PROSPECT guidelines clearly state that the benefits of fascial plane blocks are not apparent when intrathecal morphine or diamorphine is administered 4.

Decision Algorithm:

• If intrathecal morphine 50-100 μg was given: Do NOT perform TAP block 4, 7
• If NO intrathecal opioid was given: Perform bilateral TAP block with 0.25% levobupivacaine 20 mL per side 4

Adjuvant Considerations

Adding dexmedetomidine 1 μg/kg to the levobupivacaine solution significantly prolongs analgesia duration and increases patient satisfaction without additional side effects 2. However, mild sedation may occur with α2-agonist adjuvants 4.

Technical Considerations

• Perform under ultrasound guidance 1, 2
• Posterior approach provides better pain scores at 12 hours compared to lateral approach 4
• Can be administered by surgeon or anesthesiologist with equivalent efficacy 4