Transversus Abdominis Plane (TAP) Block

1. Introduction

The Transversus Abdominis Plane (TAP) block is a regional anesthesia technique that provides somatic analgesia for abdominal wall surgeries. It involves injecting local anesthetic into the neurovascular plane between the internal oblique and transversus abdominis muscles, blocking the thoracolumbar nerves (T6–L1).

✅ Indications: Postoperative pain relief in abdominal surgeries (e.g., cesarean section, hernia repair, laparotomy).

❌ Limitations: Does not provide visceral analgesia (needs multimodal analgesia).

 

2. Anatomy of the TAP Block

The anterior abdominal wall consists of:

1. External oblique muscle (outermost).

2. Internal oblique muscle (middle).

3. Transversus abdominis muscle (innermost).

🔹 Between the internal oblique and transversus abdominis lies the transversus abdominis plane (TAP), where the thoracolumbar nerves (T6–L1) travel, making it the ideal site for local anesthetic deposition.

 

✅ Innervation covered by TAP block:

• T6–T9 → Epigastrium and upper abdomen.

• T10–T12 → Umbilical and lower abdominal wall.

• L1 → Suprapubic and inguinal region.

 

3. Indications

✅ Surgeries where TAP block is beneficial

• General Surgery: Appendectomy, hernia repair, laparotomy.

• Obstetrics & Gynecology: Cesarean section, hysterectomy.

• Urology: Lower abdominal procedures.

 

4. Contraindications

❌ Absolute contraindications

• Patient refusal.

• Infection at the injection site.

• Allergy to local anesthetic.

 

❌ Relative contraindications

• Coagulopathy (risk of hematoma).

• Previous abdominal surgery (distorted anatomy).

 

5. Types of TAP Blocks

Type

Targeted Nerves

Surgical Indications

Subcostal TAP Block

T6–T9

Upper abdominal surgeries (e.g., cholecystectomy)

Classic (Lateral) TAP Block

T10–T12

Mid/lower abdominal surgeries (e.g., appendectomy)

Posterior TAP Block

T9–L1

Covers wider area, including parietal peritoneum

Quadratus Lumborum Block

T7–L2

Extended analgesia including visceral pain relief

 

6. Technique of TAP Block

A. Patient Position- Supine position with abdominal exposure.

B. Equipment

• 22G–23G blunt-tipped needle.

• Ultrasound machine (preferred).

• Local anesthetic (e.g., bupivacaine, ropivacaine).

 

C. Approaches

1. Landmark-Based Technique (Blind) – Less Preferred

1. Identify the **iliac crest and midaxillary line

2. Insert the needle perpendicular to the skin just above the iliac crest.

3. Advance through the external oblique and internal oblique muscles until a “pop” is felt, indicating entry into the TAP plane.

4. Aspirate to rule out vascular puncture, then inject local anesthetic.

❌ Limitations: Higher failure rate due to anatomical variability, lack of precision.

 

2. Ultrasound-Guided TAP Block – Preferred Approach

✅ Provides real-time visualization of anatomy, improving accuracy and safety.

1. Place a high-frequency linear probe in the midaxillary line between the costal margin and iliac crest.

2. Identify the three muscle layers:

• External oblique (superficial).

• Internal oblique (middle).

• Transversus abdominis (deepest).

3. Insert a 22G–23G needle in-plane and advance it into the plane between the internal oblique and transversus abdominis.

4. Aspirate to avoid vascular puncture and inject 20–30 mL of local anesthetic.

 

7. Local Anesthetics Used

Drug

Concentration

Dose (per side)

Duration of Action

Bupivacaine

0.25%–0.5%

20–30 mL

6–8 hours

Ropivacaine

0.2%–0.5%

20–30 mL

6–8 hours

Lidocaine

1%

20–30 mL

2–4 hours

🚨 Maximum dose of bupivacaine: 2.5 mg/kg (to avoid toxicity).

🚨 Additives like clonidine or dexmedetomidine can prolong analgesia.

 

8. Complications

Complication

Cause

Prevention

Local anesthetic systemic toxicity (LAST)

Intravascular injection

Aspirate before injecting, use ultrasound

Hematoma

Vessel injury

Avoid vascular structures

Peritoneal puncture

Needle too deep

Use ultrasound, advance cautiously

Block failure

Incorrect placement

Ensure correct spread of local anesthetic under ultrasound

 

9. Advantages of TAP Block

✅ Opioid-sparing effect → Reduces post-op opioid use.

✅ Effective for somatic pain → Improves post-op recovery.

✅ Less systemic side effects → No hemodynamic instability.

 

🚨 Limitations: Ineffective for visceral pain (needs multimodal analgesia).

 

 MCQs on TAP Block

1️⃣ Which nerves are primarily targeted in a TAP block?

a) Sciatic and femoral

b) Thoracolumbar (T6–L1) ✅

c) Phrenic and vagus

d) Ilioinguinal and iliohypogastric

 

2️⃣ Which muscle layers form the TAP plane?

a) Between rectus abdominis and peritoneum

b) Between external and internal oblique

c) Between internal oblique and transversus abdominis ✅

d) Between transversus abdominis and peritoneum

 

3️⃣ Which of the following is NOT a limitation of TAP block?

a) Inadequate visceral pain relief

b) Risk of local anesthetic toxicity

c) Hemodynamic instability ✅

d) High failure rate with landmark-based technique

 

4️⃣ Which type of TAP block is used for upper abdominal surgeries?

a) Classic TAP

b) Posterior TAP

c) Subcostal TAP ✅

d) Quadratus lumborum block