Chapter 152. Transversus Abdominis Plane (TAP) Block; Ilioinguinal and Iliohypogastric Blocks

Indications:

• Unilateral block: postoperative analgesia following inguinal hernia repair, appendectomy, renal transplant, anterior iliac crest bone harvest
• Bilateral block: median laparotomy, radical prostatectomy, hysterectomy, various laparoscopic procedures, C-section; typically performed preoperatively, except for C-section

Anatomy:

See chapter 151.

Landmarks “blind” technique:

• Patient supine, arm abducted to allow access to lateral abdomen
• Identify the triangle of Petit (delimited by latissimus dorsi, iliac crest, and external oblique):
  • Can be very difficult in obese patients
• Needle inserted perpendicular to the skin
• “Double pop” felt as needle inserted (blunt needle gives more obvious pops):
  • First pop—fascia between external and internal oblique muscles
  • Second pop—fascia between internal oblique and transverse abdominis muscles
• Twenty milliliters of local anesthesia is injected

Ultrasound technique (Figure 152-1):

• Landmarks: between costal margin and iliac crest in midaxillary line
• Muscle planes are identified with a high-frequency (8–13 MHz) probe
• Muscles are hypoechoic (dark); fascia is hyperechoic (bright)
• A 100-mm short-bevel needle inserted in-plane, anterior to posterior (i.e., from the medial side). An out-of-plane approach is also possible but requires more experience
• Inject a few milliliters of saline to ascertain correct position of needle tip
• Local deposition in the fascial layer between the internal oblique and transverse abdominis muscles; typically 15–20 mL of 0.25% bupivacaine or ropivacaine
• Oblique subcostal approach has been tried to increase block height: probe placed parallel along the costal margin, needle inserted in an in-plane technique from lateral to medial

Testing:

• Pinprick testing can be performed to assess block level
• Block is most commonly done for postoperative analgesia after induction of general anesthesia
• Block is dependent on volume, not concentration; 20 mL of 0.25% bupivacaine routinely gives 18–24 hours of analgesia

Side effects/complications:

Low-risk analgesic block:

• General risks:
  • Needle trauma
  • Intravascular injection
  • Local anesthetic toxicity
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