What is the recommended technique and dosage for a tap block using local anesthetics such as ropivacaine (generic name) or bupivacaine (generic name)?

Recommended Technique and Dosage for TAP Block

For TAP (transversus abdominis plane) block, ultrasound-guided technique is strongly recommended using 0.2-0.5 ml/kg per side of bupivacaine 0.25% or ropivacaine 0.2%, with maximum doses of 2.5 mg/kg for bupivacaine and 3 mg/kg for ropivacaine. 1

Technique Options

Ultrasound-Guided Technique (Preferred)

• Positioning: Patient supine with exposed abdomen
• Ultrasound probe: High-frequency linear probe
• Needle approach: In-plane technique for optimal visualization
• Target location: Between internal oblique and transversus abdominis muscles
• Visualization requirements:
  • Identify external oblique, internal oblique, and transversus abdominis muscles
  • Ensure needle tip visibility throughout the procedure
  • Observe local anesthetic spread between correct fascial planes

Landmark-Based Technique (Not Recommended)

• Landmark technique has been shown to have highly variable results with only 27% of injections correctly placed 2
• This technique involves identifying the lumbar triangle of Petit for needle insertion
• Due to poor accuracy and potential complications, this approach should be avoided when ultrasound is available

Recommended Dosages

For Adults:

• Bupivacaine 0.25%: 0.2-0.5 ml/kg per side (maximum 2.5 mg/kg total)
• Levobupivacaine 0.25%: 0.2-0.5 ml/kg per side (maximum 2.5 mg/kg total)
• Ropivacaine 0.2%: 0.2-0.5 ml/kg per side (maximum 3 mg/kg total)

For Children:

• Same dosing as adults, with strict adherence to weight-based calculations
• Bupivacaine 0.25%: 0.2-0.5 ml/kg per side (maximum 2.5 mg/kg total)
• Ropivacaine 0.2%: 0.2-0.5 ml/kg per side (maximum 3 mg/kg total)

Safety Considerations

Potential Complications

• Local anesthetic systemic toxicity (LAST): Cases of seizures have been reported after bilateral TAP blocks, particularly with higher concentrations 3
• Peritoneal injection: Inadvertent peritoneal injection has been reported with landmark technique 2

Risk Reduction Strategies

1. Use appropriate concentration: Lower concentrations (0.2% ropivacaine or 0.25% bupivacaine) are recommended to reduce toxicity risk
2. Calculate maximum safe dose: Always calculate based on patient weight before performing the block
3. Aspirate before injection: To avoid intravascular injection
4. Incremental injection: Administer in small aliquots with frequent aspiration
5. Have lipid emulsion available: For immediate treatment of LAST if it occurs

Adjuncts

• Preservative-free clonidine: Can be added at 1 microgram/kg per side to prolong block duration 1
• Continuous TAP catheters: Can be considered for prolonged analgesia with infusion rates of 0.1-0.3 ml/kg/hr of bupivacaine 0.25% or ropivacaine 0.2% 1, 4

Efficacy Considerations

• TAP blocks have been shown to significantly reduce perioperative opioid consumption 5
• The block primarily affects dermatomes T10-T12 4
• The ED50 (median effective analgesic dose) of ropivacaine in TAP blocks has been reported as 2.70 mg/kg, which is close to the toxic threshold 6

Remember that while TAP blocks provide excellent analgesia for abdominal wall procedures, they do not address visceral pain, which may require supplemental analgesia. Always monitor patients for signs of LAST, including perioral numbness, metallic taste, tinnitus, seizures, or cardiovascular depression.