Transversus Abdominis Plane (TAP) Block

Overview

• TAP block is a technique to provide analgesia for lower abdominal procedures.
• Involves blocking nerves in the transversus abdominis plane.

Abdominal Wall Anatomy

• Posterior Muscles:
  • Psoas major
  • Erector spinae group
  • Quadratus lumborum
  • Latissimus dorsi
• Anterior Midline:
  • Rectus abdominis muscle
• Lateral Wall Muscles:
  • Transversus abdominis (innermost)
  • Internal oblique (middle, thickest)
  • External oblique (outermost)

Nerve Anatomy

• Spinal intercostal nerves exit the vertebral foramina.
• Lie between transversus abdominis and internal oblique.
• Penetrate the rectus sheath and emerge to innervate the anterior midline.
• Branches:
  • Anterior cutaneous branch
  • Lateral cutaneous branch (innervates anterolateral and posterolateral trunk)
• Nerves travel within the transversus abdominis plane.

TAP Block Procedure

• Aim: Deposit local anesthetic in the transversus abdominis plane.
• Target: Mid-axillary line, between iliac crest and costal margin.
• Sonogram:
  • Three layers of muscle visible with subcutaneous fat above and abdominal cavity below.
  • Bright fascial line between internal oblique and transversus abdominis is the tap plane.
  • Insert needle from anterior, advance to fascial plane.

Important Landmarks and Technique

• Start scanning near abdominal midline.
• Follow muscles to mid-axillary line where transversus ends (important landmark).
• Needle Technique:
  • Approach from anterior, located within internal oblique.
  • Test injection of saline, followed by local anesthetic.
  • Use hydraulic force to separate muscle planes.
• Volume:
  • Use 25-30 mL per side.
  • Ensure careful use of anesthetic concentrations.

Applications

• Used for cesarean delivery, lower abdominal surgeries (hysterectomy, bladder surgery, oncologic procedures).
• Not ideal for procedures above the umbilicus.

Tips and Tricks

1. Tectonic Sign:
   • Use to define muscle layers when scanning.
   • Fan probe cephalocodally to identify oblique muscles.
2. Needle Insertion:
   • Hit tap plane at a shallow angle.
   • Calculate depth to the tap plane before insertion.
3. Injection Technique:
   • Use hydraulic pressure to unzipper the plane.
   • Move needle to ensure maximum spread of anesthetic.

Conclusion

• Proper technique ensures consistent and reliable nerve block outcomes.
• Importance of ensuring spread for effective analgesia.